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#1
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rusty transformers
I just got an amp with rusty power and output transformers. I have
noticed that people buy amps like this on E-bay. Does the rust short the laminations? would spraying with liquid wrench damage the transformers? How about rustolium paint? Any advice would be appreciated. |
#2
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rusty transformers
"sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. ...... Phl |
#3
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rusty transformers
sortech wrote:
I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? would spraying with liquid wrench damage the transformers? How about rustolium paint? Any advice would be appreciated. I've found that a good sanding/wire brushing to remove the rust and then several coats of black "Sharpie" permanent marker looks very nice. Raymond |
#4
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rusty transformers
On Fri, 26 Jun 2009 07:43:10 -0500, Raymond Koonce
wrote: sortech wrote: I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? would spraying with liquid wrench damage the transformers? How about rustolium paint? Any advice would be appreciated. I've found that a good sanding/wire brushing to remove the rust and then several coats of black "Sharpie" permanent marker looks very nice. Raymond Hammerite is the stuff to use. Gives the right vintage look too. d |
#5
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rusty transformers
On Fri, 26 Jun 2009 00:02:59 -0600, sortech wrote:
I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? No. would spraying with liquid wrench damage the transformers? Might, I'd not recommend any solvent on a transformer. How about rustolium paint? Sure, if that turns you on. Wipe off any rust, or clean it well without allowing solvent into the laminations. Any advice would be appreciated. |
#6
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rusty transformers
I restored a Dynaco ST-70 for a customer last year, transformers were a
rusty mess. I took the transformers off the chassis, sanded the end bells and laminate core, gave them 2 coats of primer and 2 coats of semi-gloss black. The before photo is http://www.tuberadios.com/dynaco-st70/st70notnice1.jpg and the after picture is http://www.tuberadios.com/dynaco-st70/st70nice.jpg Sal |
#7
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rusty transformers
On Jun 26, 5:52*pm, Sal wrote:
I restored a Dynaco ST-70 for a customer last year, transformers were a rusty mess. I took the transformers off the chassis, sanded the end bells and laminate core, gave them 2 coats of primer and 2 coats of semi-gloss black. The before photo is *http://www.tuberadios.com/dynaco-st70/st70notnice1..jpg and the after picture ishttp://www.tuberadios.com/dynaco-st70/st70nice.jpg Sal Very nice, Sal... like new! I would just add, wire brush or and/or steel wool. No solvents, just paint. I use "Painters Choice" and "Rustoleum" brands from Home Depot (in pressure cans), semi-gloss for lams, gloss for bells. BTW, as ugly as rust is, any rusty electrical path is of too high resistance to allow significant eddy currents in the core. Cheers, Roger |
#8
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rusty transformers
Thanks Roger,
I used Rustoleum primer and Rustoleum Semi-Gloss paint on the core and end bells, all painted separately. I lightly sanded the laminates just to remove the loose rust, the end bells, I took all the old paint off with sandpaper. Regards, Sal Engineer wrote: On Jun 26, 5:52 pm, Sal wrote: I restored a Dynaco ST-70 for a customer last year, transformers were a rusty mess. I took the transformers off the chassis, sanded the end bells and laminate core, gave them 2 coats of primer and 2 coats of semi-gloss black. The before photo is http://www.tuberadios.com/dynaco-st70/st70notnice1.jpg and the after picture ishttp://www.tuberadios.com/dynaco-st70/st70nice.jpg Sal Very nice, Sal... like new! I would just add, wire brush or and/or steel wool. No solvents, just paint. I use "Painters Choice" and "Rustoleum" brands from Home Depot (in pressure cans), semi-gloss for lams, gloss for bells. BTW, as ugly as rust is, any rusty electrical path is of too high resistance to allow significant eddy currents in the core. Cheers, Roger |
#9
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rusty transformers
Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. ..... Phl All that advice is fine Phil. WD40 might stop paint from adhering though. But what caused the rust? Water, no? The OPT could still be damp inside so it would be wise to warm up the amp to say 50C in an oven then place in a vacuum chamber so that most moisture trapped inside will then boil off and be sucked away by the vacuum pump. I always would have grave doubts about old amps that may have been in flooded premises. There must have been dozens of amps flooded in New Orleans by Katrina. Maybe they sound well with Blues music. Are the trannies varnished or waxed? if varnished, their resistance to moisture effects is better than if only waxed. If the OPT has been waxed, maybe immersing in a vat of molten wax at 110C for 4 hours will drive out water. But wax stops paint adhering, so after wax soaking the OPT should be left to drain and then the external surfaces should be cleaned with a solvent to remove wax, so the paint will stick on. Its all a painful bother, and just one reason I have never ever bought anything on E-bay. Patrick Turner. |
#10
Posted to rec.audio.tubes
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rusty transformers
"Patrick Turner" Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. All that advice is fine Phil. WD40 might stop paint from adhering though. ** I did say to " clean it off thoroughly " !!!! A rag dipped in turps is the way to do that. Worked for me.... ...... Phil |
#11
Posted to rec.audio.tubes
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rusty transformers
Phil Allison wrote: "Patrick Turner" Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. All that advice is fine Phil. WD40 might stop paint from adhering though. ** I did say to " clean it off thoroughly " !!!! A rag dipped in turps is the way to do that. Worked for me.... ..... Phil Indeed many tricks are done with rags dipped in turps..... But who here would ever think of it.... I did once pick up a Geloso 17W musicians wedding amp, or "brick" amp at as rubbish tip moments before a bulldozer would have run right over it. It had an arcing OPT with only 320Vdc. The arc was from wires outside the winding and after cleaning all the wax and carbon build up and doing slight wire relocation and re-waxing, the amp has been going well for many years. I also re-designed and re-wired it, and many little faults were fixed. Luckily the OPT and PT were not soaking wet. I sold it to a guy who had another Geloso and he wanted to have a pair. Patrick Turner. |
#12
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rusty transformers
On Jun 28, 7:33*am, Patrick Turner wrote:
Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** *No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. *Then some rust treatment like WD40 or the stuff you mentioned. *After 48 hours clean it off thorougly. *Then brush with gloss, black enamel paint. ..... * Phl All that advice is fine Phil. WD40 might stop paint from adhering though. But what caused the rust? Water, no? The OPT could still be damp inside so it would be wise to warm up the amp to say 50C in an oven then place in a vacuum chamber so that most moisture trapped inside will then boil off and be sucked away by the vacuum pump. I always would have grave doubts about old amps that may have been in flooded premises. There must have been dozens of amps flooded in New Orleans by Katrina. Maybe they sound well with Blues music. Are the trannies varnished or waxed? if varnished, their resistance to moisture effects is better than if only waxed. If the OPT has been waxed, maybe immersing in a vat of molten wax at 110C for 4 hours will drive out water. But wax stops paint adhering, so after wax soaking the OPT should be left to drain and then the external surfaces should be cleaned with a solvent to remove wax, so the paint will stick on. Its all a painful bother, and just one reason I have never ever bought anything on E-bay. Patrick Turner.- Hide quoted text - - Show quoted text - An idea about drying out an MT... one might power up the transformer with all secondaries shorted out at VERY low voltage (use a variac with current measurement plus a filament transformer, the 6.3 or 12.6 VAC sec. to mains primary winding.) Calculate the watts input and keep it low, say 10 to 15 watts. Let the transformer warm up for several hours until certainly dry. Might also work for an OPT... shoet speaker secondaries and power the P-P primay. Disclaimer: I've never done this with any transformer - outside temperature will lag power input, so could burn out windings with exterior still cold - watch all currents, power and resultant heating like a hawk! Of course, if there are enough iron losses just power it up off-load and wait until it dries out... I have done this! Cheers, Roger |
#14
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rusty transformers
"Jon Yaeger" wrote in message
... in article , Phil Allison at wrote on 6/28/09 7:41 AM: "Patrick Turner" Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. All that advice is fine Phil. WD40 might stop paint from adhering though. ** I did say to " clean it off thoroughly " !!!! A rag dipped in turps is the way to do that. Worked for me.... ..... Phil WD40 migrates and gets into all of the nooks and crannies. I certainly wouldn't use it on a rust transformer, and especially if I was going to paint it. If you are lucky, the compound will become part of the paint. If not, you've got a mess. Chemically, the major component in WD-40 is Stoddard Solvent. Other names for this include mineral spirits, solvent naphtha, aliphatic petroleum distillate, and PAINT THINNER. If the paint to be applied is alkyd or oil-based paint, there should be little problem. However, WD-40 does contain around 30 to 35 percent of "solvent dewaxed heavy paraffinic petroleum distillates" or lubricating oil. Since this is not a drying oil like linseed or tung oil, it may leave the paint slightly sticky or it may delay the drying of the paint. [Technically oil based paints do not dry, but react with oxygen in the air to cross link and polymerize. Drying oils have carbon-carbon double bonds that allow this to happen.] Wiping the transformer off with a rag soaked in paint thinner or naphtha is all that is needed to remove the lubricating oil before painting. As for rust, one of the classic books on transformer design in my library notes that allowing the laminations to rust slightly can take the place of insulating the laminations from each other. This was common practice in many inexpensive transformers in early years. One negative thing about painting a transformer is a slight reduction in the heat dissipation of the unit. Transformer life is halved for every 8 °C rise in temperature. The maximum service temperature of a transformer should be less than 60 °C for good engineering design. If you can touch the transformer laminations and keep your fingers in contact, then the transformer is not running too hot. 73, Barry WA4VZQ |
#15
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rusty transformers
"Dr. Barry L. Ornitz" Phil Allison wrote: ** What you need is a stiff wire brush, stroked along the line of the lams until no more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. Chemically, the major component in WD-40 is Stoddard Solvent. Other names for this include mineral spirits, solvent naphtha, aliphatic petroleum distillate, and PAINT THINNER. ** You fail to realsise that ALL the volatile parts of WD40 soon evaporate from a surface. If the paint to be applied is alkyd or oil-based paint, there should be little problem. ** There simply is no " thinner " there when you paint. However, WD-40 does contain around 30 to 35 percent of "solvent dewaxed heavy paraffinic petroleum distillates" or lubricating oil. ** See my instruction the "thoroughly clean" the surface ?? Since this is not a drying oil like linseed or tung oil, it may leave the paint slightly sticky or it may delay the drying of the paint. ** See my instruction the "thoroughly clean" the surface ?? Wiping the transformer off with a rag soaked in paint thinner or naphtha is all that is needed to remove the lubricating oil before painting. ** Ah - now he sees it !!!! One negative thing about painting a transformer is a slight reduction in the heat dissipation of the unit. ** Not one tiny bit likely. A black surface radiates heat far better than other colours and convection cooling is not affected by a thin layer of enamel paint. BTW In Australia " paint thinner " = acetone. And "mineral spirits" = White Spirits. ...... Phil |
#16
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rusty transformers
In article , "Dr. Barry L. Ornitz" wrote:
"Jon Yaeger" wrote in message ... in article , Phil Allison at wrote on 6/28/09 7:41 AM: "Patrick Turner" Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. All that advice is fine Phil. WD40 might stop paint from adhering though. ** I did say to " clean it off thoroughly " !!!! A rag dipped in turps is the way to do that. Worked for me.... ..... Phil WD40 migrates and gets into all of the nooks and crannies. I certainly wouldn't use it on a rust transformer, and especially if I was going to paint it. If you are lucky, the compound will become part of the paint. If not, you've got a mess. Chemically, the major component in WD-40 is Stoddard Solvent. Other names for this include mineral spirits, solvent naphtha, aliphatic petroleum distillate, and PAINT THINNER. If the paint to be applied is alkyd or oil-based paint, there should be little problem. However, WD-40 does contain around 30 to 35 percent of "solvent dewaxed heavy paraffinic petroleum distillates" or lubricating oil. Since this is not a drying oil like linseed or tung oil, it may leave the paint slightly sticky or it may delay the drying of the paint. [Technically oil based paints do not dry, but react with oxygen in the air to cross link and polymerize. Drying oils have carbon-carbon double bonds that allow this to happen.] Wiping the transformer off with a rag soaked in paint thinner or naphtha is all that is needed to remove the lubricating oil before painting. As for rust, one of the classic books on transformer design in my library notes that allowing the laminations to rust slightly can take the place of insulating the laminations from each other. This was common practice in many inexpensive transformers in early years. One negative thing about painting a transformer is a slight reduction in the heat dissipation of the unit. Transformer life is halved for every 8 °C rise in temperature. The maximum service temperature of a transformer should be less than 60 °C for good engineering design. If you can touch the transformer laminations and keep your fingers in contact, then the transformer is not running too hot. 73, Barry WA4VZQ The question arises, what is one trying to accomplish. You could use a very small amount of paint with a whole lot of mineral spirits, and that would also try to seep into the laminates and dry. Then progressively use thicker coatings. With no need to oil it up, why bother, except for a quick fix. I only redid one transformer in my life, and I used Shellac to coat the laminations. I don't think thats good stuff. Seems like Shellac absorbs moisture from what I have seen. greg |
#17
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rusty transformers
In article , "Phil Allison" wrote:
"Dr. Barry L. Ornitz" Phil Allison wrote: ** What you need is a stiff wire brush, stroked along the line of the lams until no more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. Any chemical or acid will likely just cause an uneven surface like the "POR" products. Chemically, the major component in WD-40 is Stoddard Solvent. Other names for this include mineral spirits, solvent naphtha, aliphatic petroleum distillate, and PAINT THINNER. ** You fail to realsise that ALL the volatile parts of WD40 soon evaporate from a surface. Seems like the company used to stress drying to a protective film. I thought the dry film was essentialy, varnish. Hey you could paint with WD-40 !! If the paint to be applied is alkyd or oil-based paint, there should be little problem. ** There simply is no " thinner " there when you paint. However, WD-40 does contain around 30 to 35 percent of "solvent dewaxed heavy paraffinic petroleum distillates" or lubricating oil. ** See my instruction the "thoroughly clean" the surface ?? Since this is not a drying oil like linseed or tung oil, it may leave the paint slightly sticky or it may delay the drying of the paint. ** See my instruction the "thoroughly clean" the surface ?? Wiping the transformer off with a rag soaked in paint thinner or naphtha is all that is needed to remove the lubricating oil before painting. ** Ah - now he sees it !!!! One negative thing about painting a transformer is a slight reduction in the heat dissipation of the unit. ** Not one tiny bit likely. Makes sense. A black surface radiates heat far better than other colours and convection cooling is not affected by a thin layer of enamel paint. BTW In Australia " paint thinner " = acetone. And "mineral spirits" = White Spirits. I was just using an old can of paint thinner. Under that name in parenthesis is "mineral spirts" I always thought it did the same, but was not the same. Perhaps they can charge more money for paint thinner. Any time I use acetone its gone before I can do anything with it. ...... Phil |
#18
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rusty transformers
In article , "Phil Allison" wrote:
"Dr. Barry L. Ornitz" Phil Allison wrote: ** What you need is a stiff wire brush, stroked along the line of the lams until no more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. Chemically, the major component in WD-40 is Stoddard Solvent. Other names for this include mineral spirits, solvent naphtha, aliphatic petroleum distillate, and PAINT THINNER. On my contact cleaner research page, I got an email from a guy saying in 1962 the Navy banned the use of WD-40 on hydrophones because it contained a small amount of silicone.That would be great for a paint job !!! Perhaps now the formula has changed. That would be WD-41 !! greg ** You fail to realsise that ALL the volatile parts of WD40 soon evaporate from a surface. |
#19
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rusty transformers
Rather than re-quote excessive text, let me combine several questions
and answers into one message. GregS wrote: The question arises, what is one trying to accomplish. You could use a very small amount of paint with a whole lot of mineral spirits, and that would also try to seep into the laminates and dry. Then progressively use thicker coatings. With no need to oil it up, why bother, except for a quick fix. I see no need for any oil either. Even if diluted into a very low viscosity, oil based paint between the laminations may never dry completely (*). Oxygen must diffuse through the cured film on the surface and then must diffuse down the narrow spaces between laminations. Even the paint thinner will be slow to evaporate as it has this same torturous path to diffuse through to evaporate. But when the transformer gets hot in use, the thinner will develop a considerably higher vapor pressure. It could be high enough to drive the laminations apart or harm the dried paint film on the surface. Since slightly rusty laminations do not harm the transformer, the main reason for painting is cosmetic. If the transformer buzzes, paint may help. Or you could take the transformer to a motor rewinding shop and have it vacuum impregnated with an alkyd varnish that cures (polymerizes) when heated. Glyptal is one such resin, and it has been around since the late 1920's. I only redid one transformer in my life, and I used Shellac to coat the laminations. I don't think thats good stuff. Seems like Shellac absorbs moisture from what I have seen. Shellac should work fine. It is a natural resin dissolved in alcohol. While it does absorb moisture, this should not be much of a problem with transformers. It can be a problem with wood finishes. ** You fail to realsise that ALL the volatile parts of WD40 soon evaporate from a surface. Early formulations of WD-40 had less lubricating oil than do today's versions. They would soon evaporate, usually within a few days. WD- 40 today contains much more lubricating oil, and it has a higher molecular weight. This evaporates slowly after the Stoddard solvent is gone. But its useful lifetime is now months instead of days. Seems like the company used to stress drying to a protective film. I thought the dry film was essentialy, varnish. No, they are referring to the lubricating oil. This oil has a low percentage of double bonds (chemists call this saturated) so it forms little "varnish". Varnish here refers to the films found in automotive applications, not varnish like used as wood finishes. Hey you could paint with WD-40 !! Yes but it would be like painting with water - no lasting protective coating would form. On my contact cleaner research page, I got an email from a guy saying in 1962 the Navy banned the use of WD-40 on hydrophones because it contained a small amount of silicone.That would be great for a paint job !!! Perhaps now the formula has changed. That would be WD-41 !! To the best of my knowledge, WD-40 has never contained silicones. The earliest compositions of WD-40 had mainly Stoddard solvent with small amounts of lubricating oil. This has changed over the years as now WD-40 contains up to 35% of lubricating oil. The exact composition of WD-40 changes from batch to batch depending on who supplies the solvent and oils. If the oils are more viscous, they add more solvent. Remember that all petroleum products are mixtures. I personally think the entire "story" of WD-40 is a fake. I had a chemical engineering professor who once worked at a refinery that sold to the makers of WD-40. He said that Stoddard solvent was essentially a waste product that was often burned as a fuel. Its molecular weight was too low to be diesel fuel, but too high for gasoline. I think it may be used in some high-altitude jet fuels where it lowers the cloud point temperature. When it was stored in older tanks that were riveted rather than welded, it would seep out through even very tiny cracks. This property was well known in the refining industry and it is why most penetrating oil mixtures contain Stoddard solvent. Of course, this origin was not exotic enough to sell to the public. A formulation chemist would have begun his formulation studies with a mixture similar to what is today WD-40. As another example of where the story differs from reality, the real invention of Eastman 910 adhesive, the original "superglue", is quite different than the story generally told the public. The technician who glued the prisms in the Abbe refractometer worked down the hall from my office. Soon after Fred Joyner retired, the infamous refractometer disappeared. I think it was thrown out in the trash! The chemist who Fred was working for, Harry Coover, rode his "discovery" to a Kodak vice-president's position. It appears that most websites now claim Fred Joyner was a fellow PhD to Harry Coover. He was actually Coover's technician, and I am not sure if he even had a BS in chemistry. Fred was, however, a wonderful fellow who had many tales of Eastman during its post-war growth. Fred died in 1994 if I remember correctly. 73, Barry WA4VZQ (*) Have you ever left a can of oil-based paint open for a long time? It forms a polymerized skin on top, but if you remove the skin, the paint below is usually still good. The skin will stop growing in thickness when the diffusion of oxygen through the skin stops. |
#20
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rusty transformers
Engineer wrote: On Jun 28, 7:33 am, Patrick Turner wrote: Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. ..... Phl All that advice is fine Phil. WD40 might stop paint from adhering though. But what caused the rust? Water, no? The OPT could still be damp inside so it would be wise to warm up the amp to say 50C in an oven then place in a vacuum chamber so that most moisture trapped inside will then boil off and be sucked away by the vacuum pump. I always would have grave doubts about old amps that may have been in flooded premises. There must have been dozens of amps flooded in New Orleans by Katrina. Maybe they sound well with Blues music. Are the trannies varnished or waxed? if varnished, their resistance to moisture effects is better than if only waxed. If the OPT has been waxed, maybe immersing in a vat of molten wax at 110C for 4 hours will drive out water. But wax stops paint adhering, so after wax soaking the OPT should be left to drain and then the external surfaces should be cleaned with a solvent to remove wax, so the paint will stick on. Its all a painful bother, and just one reason I have never ever bought anything on E-bay. Patrick Turner.- Hide quoted text - - Show quoted text - An idea about drying out an MT... one might power up the transformer with all secondaries shorted out at VERY low voltage (use a variac with current measurement plus a filament transformer, the 6.3 or 12.6 VAC sec. to mains primary winding.) Calculate the watts input and keep it low, say 10 to 15 watts. Let the transformer warm up for several hours until certainly dry. Might also work for an OPT... shoet speaker secondaries and power the P-P primay. Disclaimer: I've never done this with any transformer - outside temperature will lag power input, so could burn out windings with exterior still cold - watch all currents, power and resultant heating like a hawk! Of course, if there are enough iron losses just power it up off-load and wait until it dries out... I have done this! Cheers, Roger It won't work the way you say Roger. If you want to heat a tranny with current, it should be dc current, and the current applied must be carefully monitored lest you over heat the one winding that you are heating. Trouble is, moisture is merely moved from one part of the tranny to another. If a winding goes to say 105C, water boils away, but condenses elsewhere. The whole tranny must be heated to 110C to ensure moisture loss. You have to worry abou the old insulation material melting and varnish degrading which may have been used. Patrick Turner. |
#21
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rusty transformers
"Dr. Barry L. Ornitz" wrote: Rather than re-quote excessive text, let me combine several questions and answers into one message. GregS wrote: The question arises, what is one trying to accomplish. You could use a very small amount of paint with a whole lot of mineral spirits, and that would also try to seep into the laminates and dry. Then progressively use thicker coatings. With no need to oil it up, why bother, except for a quick fix. I see no need for any oil either. Even if diluted into a very low viscosity, oil based paint between the laminations may never dry completely (*). Oxygen must diffuse through the cured film on the surface and then must diffuse down the narrow spaces between laminations. Even the paint thinner will be slow to evaporate as it has this same torturous path to diffuse through to evaporate. But when the transformer gets hot in use, the thinner will develop a considerably higher vapor pressure. It could be high enough to drive the laminations apart or harm the dried paint film on the surface. Rusty laminations need to be VERY rusty before significant oxidation of the iron occurs and then rendering the iron useless in the transformer. Probably all that needs tobe done about an existing tranny's rust is to stop it getting worse which means sealing the external surfaces to prevent further moisture ingress causing more rust. So first the existing water in the tranny should be romoved with the least heating and trauma as possible, ie, 50C plus vacuum, then mechanical wire brushing and sanding followed by painting without delay, or soaking in electrical varnish and re-baking at 125C for 4 hours but only if its cetain that won't damage anything. I can't see any benefits with WD40. Since slightly rusty laminations do not harm the transformer, the main reason for painting is cosmetic. If the transformer buzzes, paint may help. Or you could take the transformer to a motor rewinding shop and have it vacuum impregnated with an alkyd varnish that cures (polymerizes) when heated. Glyptal is one such resin, and it has been around since the late 1920's. So where is Glyptal available? Is it a low vicosity liquid easily applied? tell us more about Glyptal. I only redid one transformer in my life, and I used Shellac to coat the laminations. I don't think thats good stuff. Seems like Shellac absorbs moisture from what I have seen. Shellac should work fine. It is a natural resin dissolved in alcohol. While it does absorb moisture, this should not be much of a problem with transformers. It can be a problem with wood finishes. So is polyurethane timber varnish a problem? ( Wattyl Estapol is a trade name here in Oz ) ** You fail to realsise that ALL the volatile parts of WD40 soon evaporate from a surface. Early formulations of WD-40 had less lubricating oil than do today's versions. They would soon evaporate, usually within a few days. WD- 40 today contains much more lubricating oil, and it has a higher molecular weight. This evaporates slowly after the Stoddard solvent is gone. But its useful lifetime is now months instead of days. Seems like the company used to stress drying to a protective film. I thought the dry film was essentialy, varnish. No, they are referring to the lubricating oil. This oil has a low percentage of double bonds (chemists call this saturated) so it forms little "varnish". Varnish here refers to the films found in automotive applications, not varnish like used as wood finishes. Hey you could paint with WD-40 !! Yes but it would be like painting with water - no lasting protective coating would form. On my contact cleaner research page, I got an email from a guy saying in 1962 the Navy banned the use of WD-40 on hydrophones because it contained a small amount of silicone.That would be great for a paint job !!! Perhaps now the formula has changed. That would be WD-41 !! To the best of my knowledge, WD-40 has never contained silicones. The earliest compositions of WD-40 had mainly Stoddard solvent with small amounts of lubricating oil. This has changed over the years as now WD-40 contains up to 35% of lubricating oil. The exact composition of WD-40 changes from batch to batch depending on who supplies the solvent and oils. If the oils are more viscous, they add more solvent. Remember that all petroleum products are mixtures. I personally think the entire "story" of WD-40 is a fake. I had a chemical engineering professor who once worked at a refinery that sold to the makers of WD-40. He said that Stoddard solvent was essentially a waste product that was often burned as a fuel. Its molecular weight was too low to be diesel fuel, but too high for gasoline. I think it may be used in some high-altitude jet fuels where it lowers the cloud point temperature. When it was stored in older tanks that were riveted rather than welded, it would seep out through even very tiny cracks. This property was well known in the refining industry and it is why most penetrating oil mixtures contain Stoddard solvent. Of course, this origin was not exotic enough to sell to the public. A formulation chemist would have begun his formulation studies with a mixture similar to what is today WD-40. As another example of where the story differs from reality, the real invention of Eastman 910 adhesive, the original "superglue", is quite different than the story generally told the public. The technician who glued the prisms in the Abbe refractometer worked down the hall from my office. Soon after Fred Joyner retired, the infamous refractometer disappeared. I think it was thrown out in the trash! The chemist who Fred was working for, Harry Coover, rode his "discovery" to a Kodak vice-president's position. It appears that most websites now claim Fred Joyner was a fellow PhD to Harry Coover. He was actually Coover's technician, and I am not sure if he even had a BS in chemistry. Fred was, however, a wonderful fellow who had many tales of Eastman during its post-war growth. Fred died in 1994 if I remember correctly. 73, Barry WA4VZQ (*) Have you ever left a can of oil-based paint open for a long time? It forms a polymerized skin on top, but if you remove the skin, the paint below is usually still good. The skin will stop growing in thickness when the diffusion of oxygen through the skin stops. I have observed that often. Eventually the can of paint which is only 25% full all becomes like treacle and you can't use what's under the skin. Some cans of paint go right off, and the paint all sets hard after shrinking. Polyurethane varnishes also do this ****. So, Mr "Barry" Chemist, what's the best varnish to use when winding up a tranny and where you brush on the varnish as you wind with the aim to heat the tranny later to a conveniently low temperature to make the varnish harden? Patrick Turner. |
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In article , "Dr. Barry L. Ornitz" wrote:
Rather than re-quote excessive text, let me combine several questions and answers into one message. GregS wrote: The question arises, what is one trying to accomplish. You could use a very small amount of paint with a whole lot of mineral spirits, and that would also try to seep into the laminates and dry. Then progressively use thicker coatings. With no need to oil it up, why bother, except for a quick fix. I see no need for any oil either. Even if diluted into a very low viscosity, oil based paint between the laminations may never dry completely (*). Oxygen must diffuse through the cured film on the surface and then must diffuse down the narrow spaces between laminations. Even the paint thinner will be slow to evaporate as it has this same torturous path to diffuse through to evaporate. But when the transformer gets hot in use, the thinner will develop a considerably higher vapor pressure. It could be high enough to drive the laminations apart or harm the dried paint film on the surface. Since slightly rusty laminations do not harm the transformer, the main reason for painting is cosmetic. If the transformer buzzes, paint may help. Or you could take the transformer to a motor rewinding shop and have it vacuum impregnated with an alkyd varnish that cures (polymerizes) when heated. Glyptal is one such resin, and it has been around since the late 1920's. I only redid one transformer in my life, and I used Shellac to coat the laminations. I don't think thats good stuff. Seems like Shellac absorbs moisture from what I have seen. Shellac should work fine. It is a natural resin dissolved in alcohol. While it does absorb moisture, this should not be much of a problem with transformers. It can be a problem with wood finishes. ** You fail to realsise that ALL the volatile parts of WD40 soon evaporate from a surface. Early formulations of WD-40 had less lubricating oil than do today's versions. They would soon evaporate, usually within a few days. WD- 40 today contains much more lubricating oil, and it has a higher molecular weight. This evaporates slowly after the Stoddard solvent is gone. But its useful lifetime is now months instead of days. Seems like the company used to stress drying to a protective film. I thought the dry film was essentialy, varnish. No, they are referring to the lubricating oil. This oil has a low percentage of double bonds (chemists call this saturated) so it forms little "varnish". Varnish here refers to the films found in automotive applications, not varnish like used as wood finishes. Some years ago a doctor was telling me he used WD-40 a lot on his firearms. He noticed it was developing a build up of what he called varnish. This is supposed to be the real story today..... http://www.wired.com/science/discove...st_whatsinside Hey you could paint with WD-40 !! Yes but it would be like painting with water - no lasting protective coating would form. |
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Jon wrote:
WD40 migrates and gets into all of the nooks and crannies. I certainly wouldn't use it on a rust transformer, and especially if I was going to paint it. If you are lucky, the compound will become part of the paint. If not, you've got a mess. Quite. It will leach down between the laminations, and then creep up again under the paint. If you use some other solvent to remove it, you may as well have used that to begin with. It may be compatible with some paints, but not with others. WD40 is for bodgers. A quick fix responsible for millions of subsequent catastrophic failures. And it stinks. I would brush until flat, and wipe with enough phosphoric acid to penetrate the bit of rust left between the laminations. Then after a day or two clean with a wipe of whatever solvent is appropriate for the paint, and allow to dry thoroughly. The most important thing for a lasting finish is to ensure there is no damp remaining between the laminations, which will cause more rust under the paint. The paint should be hard or it will soon rub off the corners. If it can't be baked, a two-part paint such as epoxy should be considered, because normal air drying paints take months to harden. Ian |
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In article , "Ian Iveson" wrote:
Jon wrote: WD40 migrates and gets into all of the nooks and crannies. I certainly wouldn't use it on a rust transformer, and especially if I was going to paint it. If you are lucky, the compound will become part of the paint. If not, you've got a mess. Quite. It will leach down between the laminations, and then creep up again under the paint. If you use some other solvent to remove it, you may as well have used that to begin with. It may be compatible with some paints, but not with others. WD40 is for bodgers. A quick fix responsible for millions of subsequent catastrophic failures. And it stinks. I would brush until flat, and wipe with enough phosphoric acid to penetrate the bit of rust left between the laminations. Then after a day or two clean with a wipe of whatever solvent is appropriate for the paint, and allow to dry thoroughly. The most important thing for a lasting finish is to ensure there is no damp remaining between the laminations, which will cause more rust under the paint. Not many transformers are completly sealed. The paint should be hard or it will soon rub off the corners. If it can't be baked, a two-part paint such as epoxy should be considered, because normal air drying paints take months to harden. Why would it rub off the corners if no contact is being made? It does not have to be epoxy to dry fast. Automobile paint usually comes with a hardner additive, which you add like and epoxy mix, which makes it pretty dry in a day or two. If you don't add the hardner it takes, or took me several months, even with some heat applied, just to get it hard enought to buff. Still was no way near hard like if I would have added the hardner. This was on a car I was detailing last year. I played with the phosphoric acid last year on the car. One thing it does not do is penetrate through all rust layers. What you end up with is a hard coating over remaining rust. The rust layer cannot be thick to work well. I really don't think phosphoric acid is going to get through the laminations. I do have some old Dupont prep which is alcohol based. Phosphoric acid and alcohol. You can probably mix with alcohol to get a better seep into the laminations, if thats what you want to do. greg greg |
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On Jun 30, 5:18*am, Patrick Turner wrote:
Engineer wrote: On Jun 28, 7:33 am, Patrick Turner wrote: Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** *No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. *Then some rust treatment like WD40 or the stuff you mentioned. *After 48 hours clean it off thorougly. *Then brush with gloss, black enamel paint. ..... * Phl All that advice is fine Phil. WD40 might stop paint from adhering though. But what caused the rust? Water, no? The OPT could still be damp inside so it would be wise to warm up the amp to say 50C in an oven then place in a vacuum chamber so that most moisture trapped inside will then boil off and be sucked away by the vacuum pump. I always would have grave doubts about old amps that may have been in flooded premises. There must have been dozens of amps flooded in New Orleans by Katrina. Maybe they sound well with Blues music. Are the trannies varnished or waxed? if varnished, their resistance to moisture effects is better than if only waxed. If the OPT has been waxed, maybe immersing in a vat of molten wax at 110C for 4 hours will drive out water. But wax stops paint adhering, so after wax soaking the OPT should be left to drain and then the external surfaces should be cleaned with a solvent to remove wax, so the paint will stick on. Its all a painful bother, and just one reason I have never ever bought anything on E-bay. Patrick Turner.- Hide quoted text - - Show quoted text - An idea about drying out an MT... one might power up the transformer with all secondaries shorted out at VERY low voltage (use a variac with current measurement plus a filament transformer, the 6.3 or 12.6 VAC sec. to mains primary winding.) Calculate the watts input and keep it low, say 10 to 15 watts. *Let the transformer warm up for several hours until certainly dry. Might also work for an OPT... shoet speaker secondaries and power the P-P primay. Disclaimer: I've never done this with any transformer - outside temperature will lag power input, so could burn out windings with exterior still cold - watch all currents, power and resultant heating like a hawk! Of course, if there are enough iron losses just power it up off-load and wait until it dries out... *I have done this! Cheers, Roger It won't work the way you say Roger. If you want to heat a tranny with current, it should be dc current, and the current applied must be carefully monitored lest you over heat the one winding that you are heating. Trouble is, moisture is merely moved from one part of the tranny to another. If a winding goes to say 105C, water boils away, but condenses elsewhere. The whole tranny must be heated to 110C to ensure moisture loss. You have to worry abou the old insulation material melting and varnish degrading which may have been used. Patrick Turner.- Hide quoted text - - Show quoted text - Patrick, you have a point, but I was not thinking of boiling water off, rather just getting the transformer warm enough to let any moisture evaporate slowly before painting... say 50 deg.C for 48 hours, or as long as it needs to heat soak. BTW, what's wrong with AC to heat the windings? As you know, S/C testing produces I^2.R losses, only, heating the copper with no iron losses to speak of. But open circuit (no load) core heating is from iron losses, if there are enough of them - might be better for drying as it's "more inside". I have at least one MT that gets quite warm under O/C testing and it doesn't have shorted turns. I have others that stay virtually stone cold if unloaded and barely warm up on normal load. Another, in a circa-1960's Phillips table-top radio, gets very hot under normal load but I don't think it has shorted turns - it's just a nasty component! I sold the radio (it's still working fine!) Cheers, Roger |
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"GregS" wrote in message
... Why would it rub off the corners if no contact is being made? It does not have to be epoxy to dry fast. Automobile paint usually comes with a hardner additive, which you add like and epoxy mix, which makes it pretty dry in a day or two. If you don't add the hardner it takes, or took me several months, even with some heat applied, just to get it hard enought to buff. Still was no way near hard like if I would have added the hardner. This was on a car I was detailing last year. The manufacturers of early epoxy resins for the public should have done a better job of naming the ingredients. The "resin" is actually a monomer or short chain polymer having an epoxide group at both ends. The "hardener" is a polyamine monomer. Epoxy is a co-polymer formed when resin reacts with the hardener, and both need to be in approximately equal parts. Compare this to unsaturated polyester resins (like Bondo) which need a polymerization catalyst like methyl-ethyl-ketone peroxide to start the reaction. Polyester resins will react without the catalyst, albeit slowly. I am amazed your epoxy hardened at all. I played with the phosphoric acid last year on the car. One thing it does not do is penetrate through all rust layers. What you end up with is a hard coating over remaining rust. The rust layer cannot be thick to work well. I really don't think phosphoric acid is going to get through the laminations. I do have some old Dupont prep which is alcohol based. Phosphoric acid and alcohol. You can probably mix with alcohol to get a better seep into the laminations, if thats what you want to do. The phosphoric acid reacts with red iron oxides to convert them to a tightly adhering black iron phosphate. This will actually prevent further rusting under the phosphate. Most of the rust should be removed mechanically before the phosphoric acid is applied, as you note. Let the iron phosphate dry very thoroughly before painting. 73, Barry WA4VZQ |
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"GregS" wrote in message
... Some years ago a doctor was telling me he used WD-40 a lot on his firearms. He noticed it was developing a build up of what he called varnish. Yes, there is a small amount of hydrocarbons in WD-40 with covalent bonds. These can oxidize and form a gummy residue similar to paint or varnish. Gasoline when stored for a while, exposed to air, can form varnish too. This is supposed to be the real story today..... http://www.wired.com/science/discove...st_whatsinside It took many tries before this would load. I am not terribly impressed with their results. Most certainly, the alkanes are not all linear chains. And if cyclics like dimethyl naphthalene and cyclohexane are present, there will be other cyclics and isoalkanes by the score. They should have performed simulated distillation with the chromatograph. This ramps its temperature up slowly so the less volatile components will elude from the GC column. WD-40 has significant levels of C18 through C22 hydrocarbons with lower levels of even higher molecular weight hydrocarbons. The manufacturer will not publically divulge what anti-oxidant is used in WD-40. I suspect that something in the hydroquinone family or either tocopherol (Vitamin E) is used for this. Wired needs a better lab! Barry |
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"Patrick Turner" wrote in message
... So where is Glyptal available? Is it a low vicosity liquid easily applied? tell us more about Glyptal. Glyptal was one of the earliest alkyd varnishes. Its name comes from GLYcerin and PhThALic acid, the ingredients used to make it. These ingredients were combined in a condensation polymerization reaction to produce a low molecular weight liquid polymer. This is applied and then heated to further polymerize and cross-link, thereby creating the final cured coating. Most motor rewinding shops have it or an alternative material for vacuum impregnating motor coils and transformers. They also have the large ovens for baking it. Many of these coatings are available from the Glyptal Company (formerly a part of General Electric). See: http://www.glyptal.com for details. Getting just a gallon or two from them may be difficult. Fortunately Caswell Plating carries it, http://www.caswellplating.com/aids/glyptal.html#. It cannot be shipped by air, but UPS (United Package Smashers) will carry it. So is polyurethane timber varnish a problem? ( Wattyl Estapol is a trade name here in Oz ) The oil based varnish should do well too but read on... So, Mr "Barry" Chemist, what's the best varnish to use when winding up a tranny and where you brush on the varnish as you wind with the aim to heat the tranny later to a conveniently low temperature to make the varnish harden? Patrick Turner. Well, to start, my degrees are in chemical and electrical engineering, not chemistry. But I am not offended. :-) One of my hobbies is restoring Boatanchors, which are what ham radio operators affectionately call vacuum tube radios. The name comes from the military surplus radios flooding the market after WWII. I used to be active in a mail reflector specific to vacuum tube radios. Since I was the one who usually answered questions about glyptal, MPF (moisture and fungus proofing), wrinkle finish paint, PCBs (polychlorinated biphenyls), cellulose ester plastics, and other sundry antique radio stuff, I was respectfully called the "resident chemist" by the group. Earlier this evening, I wrote some recommendations for PCB cleanup for Alan, VK2DRR. He was restoring a venerable old AR88 receiver whose oil filled caps were leaking. I consider Morris, VK3DOC, another restorer of Boatanchors, one of my closest friends. One of these days, I plan to visit him down under. It has been my experience that Aussie hams were some of the most resourceful hams I have ever met. Instead of applying Glyptal, or another insulating varnish, by hand, layer by layer, I suggest visiting a large motor rewinding shop. They usually have the facilities for vacuum impregnation and they are a good source for enameled wire too. I have had a large transformer coated and baked for just a few dollars. The shop also supplied "fish paper" and Nomex high temperature insulating cloth. Making a friend there is well worth your while. You can pick up lots of useful tips for nothing more than the cost of a few cups of coffee and a box of doughnuts. 73 (amateur radio for Best Regards), Barry WA4VZQ |
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In article , "Dr. Barry L. Ornitz" wrote:
"Patrick Turner" wrote in message ... So where is Glyptal available? Is it a low vicosity liquid easily applied? tell us more about Glyptal. Glyptal was one of the earliest alkyd varnishes. Its name comes from GLYcerin and PhThALic acid, the ingredients used to make it. These i Instead of applying Glyptal, or another insulating varnish, by hand, layer by layer, I suggest visiting a large motor rewinding shop. They usually have the facilities for vacuum impregnation and they are a good source for enameled wire too. I have had a large transformer coated and baked for just a few dollars. The shop also supplied "fish paper" and Nomex high temperature insulating cloth. Making a friend there is well worth your while. You can pick up lots of useful tips for nothing more than the cost of a few cups of coffee and a box of doughnuts. 73 (amateur radio for Best Regards), Barry WA4VZQ I went to a shop in the early 80's. Some woman was in charge of a bunch of workers. It was mostly a transformer shop. I got copper wire for cheap along with free mica tape and laminations. greg |
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In article , "Dr. Barry L. Ornitz" wrote:
Rather than re-quote excessive text, let me combine several questions and answers into one message. GregS wrote: The question arises, what is one trying to accomplish. You could use a very small amount of paint with a whole lot of mineral spirits, and that would also try to seep into the laminates and dry. Then progressively use thicker coatings. With no need to oil it up, why bother, except for a quick fix. I see no need for any oil either. Even if diluted into a very low viscosity, oil based paint between the laminations may never dry On my contact cleaner research page, I got an email from a guy saying in 1962 the Navy banned the use of WD-40 on hydrophones because it contained a small amount of silicone.That would be great for a paint job !!! Perhaps now the formula has changed. That would be WD-41 !! To the best of my knowledge, WD-40 has never contained silicones. The earliest compositions of WD-40 had mainly Stoddard solvent with small amounts of lubricating oil. This has changed over the years as now WD-40 contains up to 35% of lubricating oil. The exact composition of WD-40 changes from batch to batch depending on who supplies the solvent and oils. If the oils are more viscous, they add more solvent. Remember that all petroleum products are mixtures. I don't know if it was true, and I don't know what Navy.(US) That was from a person who I will quote below.. As WD-40 contains small amounts of silicone, we advise against its use. The problem with any product containing silicone it that when it is exposed to salt, it can form 'waterglass', which ie an excellent insulator and it is very difficult to remove! In 1962, the US navy banned its use in sonar hydrophones for that reason. I have friends who are commercial pilots who sprayed it on wing-flap hinges; the consequence was that the skin of the flap developed hairline cracks. The normal technique of 'Stop drilling' did not prevent the propagation of the crack. Wm. M. Wright, CEO S. W. Electrochemicals Ltd. |
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"GregS" wrote in message
... I don't know if it was true, and I don't know what Navy.(US) That was from a person who I will quote below.. As WD-40 contains small amounts of silicone, we advise against its use. The problem with any product containing silicone it that when it is exposed to salt, it can form 'waterglass', which ie an excellent insulator and it is very difficult to remove! In 1962, the US navy banned its use in sonar hydrophones for that reason. I have friends who are commercial pilots who sprayed it on wing-flap hinges; the consequence was that the skin of the flap developed hairline cracks. The normal technique of 'Stop drilling' did not prevent the propagation of the crack. This still sounds like a Navy fish story to me. Waterglass is sodium silicate and it is trivial to remove as it dissolves in water; it also is an electrical conductor when wet. Also silicones are very resistant to salt solutions. Not many things attack silicone. A few that do include the now banned dichloro-difluoro-ethylene which is a good solvent for low molecular weight silicones, and strong caustics like concentrated potassium hydroxide and sodium hydroxide. In fact, silicone potting compounds are used in hydrophone construction. Silicone compounds have been used since WWII to encapsulate the Rochelle salt piezoelectric crystals. What I suspect was happening to the hydrophones was the use of one-part silicone which, when it cures, releases acetic acid (some newer silicones release alcohols which are much more benign). One-part silicones will not cure deeper than a centimeter or so too. For deep section cures, two part silicones are needed as they need no the exposure to air and do not release any reaction byproducts. Eastman Chemical Company learned this the hard way when they tried to seal some thermocouples used in their coal gasifier. I was called in from their research labs to find out why their thermocouple life was so short. Switching to two-part silicones cured half of their problems. The other half of the problems required the assistance of one of the plant metallurgists. WD-40 provides very little long-term lubrication, especially early formulations of WD-40. With air flowing past the hinges at high velocity, the evaporation of WD-40 would increase leaving the hinges with NO lubrication. But the cracks appear much more like stress corrosion cracking than anything in WD-40. I know of no ingredients in WD-40 that would cause stress corrosion cracking. Does your friend, perchance, sell his own version of WD-40? It sure sounds like he is stretching facts to dissuade people from using WD-40. Barry |
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On Jul 1, 9:08*pm, "Dr. Barry L. Ornitz"
wrote: "GregS" wrote in message ... I don't know if it was true, and I don't know what Navy.(US) That was from a person who I will quote below.. As WD-40 contains small amounts of silicone, we advise against its use. The problem with any product containing silicone it that when it is exposed to salt, it can form 'waterglass', which ie an excellent insulator and it is very difficult to remove! In 1962, the US navy banned its use in sonar hydrophones for that reason. I have friends who are commercial pilots who sprayed it on wing-flap hinges; the consequence was that the skin of the flap developed hairline cracks. The normal technique of 'Stop drilling' did not prevent the propagation of the crack. This still sounds like a Navy fish story to me. *Waterglass is sodium silicate and it is trivial to remove as it dissolves in water; it also is an electrical conductor when wet. *Also silicones are very resistant to salt solutions. *Not many things attack silicone. *A few that do include the now banned dichloro-difluoro-ethylene which is a good solvent for low molecular weight silicones, and strong caustics like concentrated potassium hydroxide and sodium hydroxide. *In fact, silicone potting compounds are used in hydrophone construction. *Silicone compounds have been used since WWII to encapsulate the Rochelle salt piezoelectric crystals. What I suspect was happening to the hydrophones was the use of one-part silicone which, when it cures, releases acetic acid (some newer silicones release alcohols which are much more benign). *One-part silicones will not cure deeper than a centimeter or so too. *For deep section cures, two part silicones are needed as they need no the exposure to air and do not release any reaction byproducts. *Eastman Chemical Company learned this the hard way when they tried to seal some thermocouples used in their coal gasifier. *I was called in from their research labs to find out why their thermocouple life was so short. *Switching to two-part silicones cured half of their problems. *The other half of the problems required the assistance of one of the plant metallurgists. WD-40 provides very little long-term lubrication, especially early formulations of WD-40. *With air flowing past the hinges at high velocity, the evaporation of WD-40 would increase leaving the hinges with NO lubrication. *But the cracks appear much more like stress corrosion cracking than anything in WD-40. *I know of no ingredients in WD-40 that would cause stress corrosion cracking. Does your friend, perchance, sell his own version of WD-40? *It sure sounds like he is stretching facts to dissuade people from using WD-40. * * * * Barry This is a really great thread. WD 40. Well its the best selling bodge-tastic do it all nothingness that exists. It does have its uses though. When I worked at Dowtys they used to buy it in 5 gallon drums (expensive). We used it as a first shot at freeing a broken stud/bolt etc. Sometimes it worked although 90 percent of the time we ended up drilling/grinding and generally munching the thing out. I still use it now as cutting fluid for aluminium alloys. On the last fine cut you really cant beat it, although unless you can afford it just use normal parafin for roughing out. I have some old Rocol branded stuff that is the best penetrating fluid. Its solvent is "trike" 111, dont ask me to spell it although I know its banned (builds up in your liver) great stuff for killing flies too. Anyway as for WD 40 I am certain it contains silicone because if you have it anywhere near your prep work for painting you end up with blotches (and the paint). You can even use it to advantage if you want a Hammerite type finish. Cheers Matt. I agree about the waterglass nonesense. Its jelly like, disolves in water and is no real problem |
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"bigwig = bigwank " WD 40. Well its the best selling bodge-tastic do it all nothingness that exists. ** Funny how so many folk find it so useful - then. Anyway as for WD 40 I am certain it contains silicone.. ** It says right on the can " No Silicone. No kerosene ". But ****wits like YOU can never be convinced of anything. .... Phil |
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rusty transformers
Engineer wrote: On Jun 30, 5:18 am, Patrick Turner wrote: Engineer wrote: On Jun 28, 7:33 am, Patrick Turner wrote: Phil Allison wrote: "sortech" I just got an amp with rusty power and output transformers. I have noticed that people buy amps like this on E-bay. Does the rust short the laminations? ** No. would spraying with liquid wrench damage the transformers? ** What you need is a stiff wire brush, stroked along the line of the lams until nothing more comes off. Then some rust treatment like WD40 or the stuff you mentioned. After 48 hours clean it off thorougly. Then brush with gloss, black enamel paint. ..... Phl All that advice is fine Phil. WD40 might stop paint from adhering though. But what caused the rust? Water, no? The OPT could still be damp inside so it would be wise to warm up the amp to say 50C in an oven then place in a vacuum chamber so that most moisture trapped inside will then boil off and be sucked away by the vacuum pump. I always would have grave doubts about old amps that may have been in flooded premises. There must have been dozens of amps flooded in New Orleans by Katrina. Maybe they sound well with Blues music. Are the trannies varnished or waxed? if varnished, their resistance to moisture effects is better than if only waxed. If the OPT has been waxed, maybe immersing in a vat of molten wax at 110C for 4 hours will drive out water. But wax stops paint adhering, so after wax soaking the OPT should be left to drain and then the external surfaces should be cleaned with a solvent to remove wax, so the paint will stick on. Its all a painful bother, and just one reason I have never ever bought anything on E-bay. Patrick Turner.- Hide quoted text - - Show quoted text - An idea about drying out an MT... one might power up the transformer with all secondaries shorted out at VERY low voltage (use a variac with current measurement plus a filament transformer, the 6.3 or 12.6 VAC sec. to mains primary winding.) Calculate the watts input and keep it low, say 10 to 15 watts. Let the transformer warm up for several hours until certainly dry. Might also work for an OPT... shoet speaker secondaries and power the P-P primay. Disclaimer: I've never done this with any transformer - outside temperature will lag power input, so could burn out windings with exterior still cold - watch all currents, power and resultant heating like a hawk! Of course, if there are enough iron losses just power it up off-load and wait until it dries out... I have done this! Cheers, Roger It won't work the way you say Roger. If you want to heat a tranny with current, it should be dc current, and the current applied must be carefully monitored lest you over heat the one winding that you are heating. Trouble is, moisture is merely moved from one part of the tranny to another. If a winding goes to say 105C, water boils away, but condenses elsewhere. The whole tranny must be heated to 110C to ensure moisture loss. You have to worry abou the old insulation material melting and varnish degrading which may have been used. Patrick Turner.- Hide quoted text - - Show quoted text - Patrick, you have a point, but I was not thinking of boiling water off, rather just getting the transformer warm enough to let any moisture evaporate slowly before painting... say 50 deg.C for 48 hours, or as long as it needs to heat soak. 50C for all week long still won't dry out the tranny thouroughly. BTW, what's wrong with AC to heat the windings? Its because you have to apply fairly high voltages, and if there is a HV secondary and water present maybe you get arcing. The application of dc means voltages are all very low and the coils heat up according to I*R. But the cores don't heat from the dc; the coils heat and transfer heat to the core, so you need to wrap the item in a blanket and allow time for the heat to soak out into the core. Very tricky. In many PT, with no load and applied ac, the cores don't heat up much at all, unless you raise the applied voltage to push the cores into saturation, and then you get high current peaks and copper heating as well. I don't lke any of these techniques, and using an oven to heat up a tranny to 50C then place it in a vacuum chamber, and a compressor set up to suck rather than blow will do from a suitable enclosure and a small dia hose pipe. As you know, S/C testing produces I^2.R losses, only, heating the copper with no iron losses to speak of. But open circuit (no load) core heating is from iron losses, if there are enough of them - might be better for drying as it's "more inside". I have at least one MT that gets quite warm under O/C testing and it doesn't have shorted turns. I have others that stay virtually stone cold if unloaded and barely warm up on normal load. Another, in a circa-1960's Phillips table-top radio, gets very hot under normal load but I don't think it has shorted turns - it's just a nasty component! I sold the radio (it's still working fine!) Cheers, Roger Many cheap radios had 30C rise in temp above ambient. It means that on a 30C day the PT rises to 60C, ouch! Many were designed like that and had ordinary paper insulation thatafter 60 years goes very dry and brittle. Sometimes you can extend life by soaking the tranny when it is dry in varnish and baking it. Patrick Turner. |
#36
Posted to rec.audio.tubes
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rusty transformers
"Dr. Barry L. Ornitz" wrote: "Patrick Turner" wrote in message ... So where is Glyptal available? Is it a low vicosity liquid easily applied? tell us more about Glyptal. Glyptal was one of the earliest alkyd varnishes. Its name comes from GLYcerin and PhThALic acid, the ingredients used to make it. These ingredients were combined in a condensation polymerization reaction to produce a low molecular weight liquid polymer. This is applied and then heated to further polymerize and cross-link, thereby creating the final cured coating. Most motor rewinding shops have it or an alternative material for vacuum impregnating motor coils and transformers. They also have the large ovens for baking it. There are suppliers selling "electrical varnish" that pongs badly while using it and which hardens in air, but not under layers of wire and insulation unless heated at 125C for 4 hours. I have no idae if its Glyptal. Many of these coatings are available from the Glyptal Company (formerly a part of General Electric). See: http://www.glyptal.com for details. Getting just a gallon or two from them may be difficult. Fortunately Caswell Plating carries it, http://www.caswellplating.com/aids/glyptal.html#. It cannot be shipped by air, but UPS (United Package Smashers) will carry it. So is polyurethane timber varnish a problem? ( Wattyl Estapol is a trade name here in Oz ) The oil based varnish should do well too but read on... It doesn't seem to really go very hard after heating. Sort of mushy, and then its easy to over heat it and its brittle. So, Mr "Barry" Chemist, what's the best varnish to use when winding up a tranny and where you brush on the varnish as you wind with the aim to heat the tranny later to a conveniently low temperature to make the varnish harden? Patrick Turner. Well, to start, my degrees are in chemical and electrical engineering, not chemistry. But I am not offended. :-) One of my hobbies is restoring Boatanchors, which are what ham radio operators affectionately call vacuum tube radios. The name comes from the military surplus radios flooding the market after WWII. I used to be active in a mail reflector specific to vacuum tube radios. Since I was the one who usually answered questions about glyptal, MPF (moisture and fungus proofing), wrinkle finish paint, PCBs (polychlorinated biphenyls), cellulose ester plastics, and other sundry antique radio stuff, I was respectfully called the "resident chemist" by the group. Earlier this evening, I wrote some recommendations for PCB cleanup for Alan, VK2DRR. He was restoring a venerable old AR88 receiver whose oil filled caps were leaking. I consider Morris, VK3DOC, another restorer of Boatanchors, one of my closest friends. One of these days, I plan to visit him down under. It has been my experience that Aussie hams were some of the most resourceful hams I have ever met. I have 3 AR88 and several other old radios waiting for the day when I get some time to maybe make 1 or two really good AR88 from the 3 I have. I inherited them and in an uncompleted state, with some spare parts from an old guy whose time ran out. Plus I got several pick up loads of other junk, so I had to build serious storage to accomodate it, then tell myself never again...... Instead of applying Glyptal, or another insulating varnish, by hand, layer by layer, I suggest visiting a large motor rewinding shop. They usually have the facilities for vacuum impregnation and they are a good source for enameled wire too. There is a guy here who I did visit for just that purpose but he didn't ever use a vacuum chamber for the motors he re-wound because was no need. The varnish just soaks in easily to motor windings because there are no flat thin windings between cheeks with insulation tightly fitting to prevent vanish ingress. I hunted around for someone with a vac chamber but no luck. So I made a vac chamber. The trouble is that I can submerge a warmed up item in a can of varnish within the vac chamber, and draw the vacuum, but the big risk is that the varnish boils at the lower pressure then gets into the vaccum pump, where it causes grief to the piston and its sealing rings and valves. YUK!. I stuffed an old fridge compressor I was using backwards. Now I have a 1HP painter's compressor, and I don't want to **** that up. The vacuum I get is only 95%, but good enough. I have had a large transformer coated and baked for just a few dollars. The shop also supplied "fish paper" and Nomex high temperature insulating cloth. Making a friend there is well worth your while. You can pick up lots of useful tips for nothing more than the cost of a few cups of coffee and a box of doughnuts. Well, sometimes the guys at the motor re-winders are not all that friendly. The ones I knew are rather surly, and always busy worrying about everything, and never take time off during working hours for coffee and a dougnut. After working hours they rush off home; they can't bear to stay another minute. And the soak method is unreliable for PT or OPT. One gave me 4L can of varnish for its cost price, but next time I enquired he said he didn't want to give me any. They don't like having to keep ordering it in bulk more often. The slighytest thing thay did for me always cost money, so I figured I needed to be independant. And you have not ansered my question, what's the best goop that you can paint with a paint brush on while winding neat layers, and then heat afterwards to a temperature not exceeding say 60C? It needs to be able to adhere to polythene or polyester. I'm used to the stuff that hardens at 125C after 4+ hours. Very smelly while whatever solvent is boiled off and whatever else. For my oven, I use an old electric frypan with a lid that has been increased in height to take largish PT with say a 2kW rating. The temp control appears to be OK and if I set it at 260F the varnish does appear to go dry and hard under the outer layers of clear coloured insulation around an item. If it ain't baked enough, you can see that the varnish is still liquid and squishy under the insulation. Further within the winding things would be worse. I wanted something that didn't need such a high temp and thus gave me some leeway against melting insulation. I have used Wattyl 7008 floor varnish which comes equal cans of part A and partB which you mix as you need it. Its also terrible to use while winding because it gets everywhere and on your hands and stinks like hell. You need a can of methylated spirts and cloth to keep cleaning hands and your fingers are black for a week afterwards. Lord knows what the fumes do to lungs. Its good stuff though because its pot life is 8 hours, and you paint it on generously and you can clamp up layered tranny winding between blocks of wood to make sure the height of winding gets down to what you've calculated so the E&I lams will fit in later. Next day the clamps are removed, and the winding stays down to the clamped dimensions, and insertion of E&I is easy. But it doesn't stick very well to other plastics used for interlayer insulation, so in an OPT you can get some howl because there is still some microscopic vibration possible between where things have little adherance. What appears to howl ther least is a compound that does not harden completely, but which stays a bit gooey, sort of like tars or heavy waxes, so that itm is damped rather than glued together. Tars of course are usless for varnishing; they are far too viscous but are ideal for potting compound, and they are cheap. Trouble is the local road emoleum used here is liquid at 60C, and even at 30C it will run slowly out of a pot used for potting a tranny. The roofer's pitch won't run at 30C or even 60C, but you need to heat it to 150C to use it, so when its poured in around a tranny in a can you have to allow a big space so it gets in without setting hard as it cools against items in the can. I tried waxes, but they melt too easily, and you get pools of it under amps on a warm day. I tried styrene as a hardener but it did virtually nothing to improve matters. Corboba wax was not much better and it shrank a lot after it had cooled. The real mc'coy potting compound is a terribler price!. Good stuff, but like the casting resin I now use for potting, but if you ever need to re-wind the tranny its extremely difficult to remove the core. For a usless tranny with a shorted turn or open winding I generally place the itm in a wood fire after drilling a few holes to let vapors under pressure get out without explosions. When I cansee the core is just dull read then next day the mess will fall apart and I can recover the lams. But it doesn't work with toroids or C-cores because the lams are strips glued together with epoxy glue of some kind, but I am not sure what though. I have an open fireplace with a door that closes down and the terrible smelling smoke goes up the chimney late at night. I don't do it often. From what I have observed, the cores magnetic performance does not suffer from the heating. They are used later in chokes where core material is not critical. The fire vaporizes any plastics, and the wire can be easily cut free for the re-cycle bin. The varnish between lams is also vaporized and the tranny is easy to dismantle. So if ever a house with a huge collection of boat anchor electronics burns down, at least there will be a pile of cores somewhere for that dedicated old bugger somewhere who will beging to re-build. Patrick Turner. 73 (amateur radio for Best Regards), Barry WA4VZQ |
#37
Posted to rec.audio.tubes
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rusty transformers
In article , "Dr. Barry L. Ornitz" wrote:
"GregS" wrote in message ... I don't know if it was true, and I don't know what Navy.(US) That was from a person who I will quote below.. As WD-40 contains small amounts of silicone, we advise against its use. The problem with any product containing silicone it that when it is exposed to salt, it can form 'waterglass', which ie an excellent insulator and it is very difficult to remove! In 1962, the US navy banned its use in sonar hydrophones for that reason. I have friends who are commercial pilots who sprayed it on wing-flap hinges; the consequence was that the skin of the flap developed hairline cracks. The normal technique of 'Stop drilling' did not prevent the propagation of the crack. This still sounds like a Navy fish story to me. Waterglass is sodium silicate and it is trivial to remove as it dissolves in water; it also is WD-40 provides very little long-term lubrication, especially early formulations of WD-40. With air flowing past the hinges at high velocity, the evaporation of WD-40 would increase leaving the hinges with NO lubrication. But the cracks appear much more like stress corrosion cracking than anything in WD-40. I know of no ingredients in WD-40 that would cause stress corrosion cracking. Does your friend, perchance, sell his own version of WD-40? It sure sounds like he is stretching facts to dissuade people from using WD-40. He sells Stabilant. http://www.stabilant.com/ I got to using Tal 5 from WD-40 company, then they quit making it. I explained they should have made the can look more like the WD-40 can. It was a better lubricator. I use a lot of CRC 2-26 lately. My favorite all purpose liquid. greg |
#38
Posted to rec.audio.tubes
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rusty transformers
In article , "Phil Allison" wrote:
"bigwig = bigwank " WD 40. Well its the best selling bodge-tastic do it all nothingness that exists. ** Funny how so many folk find it so useful - then. Anyway as for WD 40 I am certain it contains silicone.. ** It says right on the can " No Silicone. No kerosene ". But ****wits like YOU can never be convinced of anything. .... Phil I never thought of WD-40 as containing silicone. It never ever seemed to have any silicone slippery feel when dry. greg |
#39
Posted to rec.audio.tubes
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rusty transformers
In article , (GregS) wrote:
In article , "Dr. Barry L. Ornitz" wrote: "GregS" wrote in message ... I don't know if it was true, and I don't know what Navy.(US) That was from a person who I will quote below.. As WD-40 contains small amounts of silicone, we advise against its use. The problem with any product containing silicone it that when it is exposed to salt, it can form 'waterglass', which ie an excellent insulator and it is very difficult to remove! In 1962, the US navy banned its use in sonar hydrophones for that reason. I have friends who are commercial pilots who sprayed it on wing-flap hinges; the consequence was that the skin of the flap developed hairline cracks. The normal technique of 'Stop drilling' did not prevent the propagation of the crack. This still sounds like a Navy fish story to me. Waterglass is sodium silicate and it is trivial to remove as it dissolves in water; it also is WD-40 provides very little long-term lubrication, especially early formulations of WD-40. With air flowing past the hinges at high velocity, the evaporation of WD-40 would increase leaving the hinges with NO lubrication. But the cracks appear much more like stress corrosion cracking than anything in WD-40. I know of no ingredients in WD-40 that would cause stress corrosion cracking. Does your friend, perchance, sell his own version of WD-40? It sure sounds like he is stretching facts to dissuade people from using WD-40. He sells Stabilant. http://www.stabilant.com/ I got to using Tal 5 from WD-40 company, then they quit making it. I explained they should have made the can look more like the WD-40 can. It was a better lubricator. I use a lot of CRC 2-26 lately. My favorite all purpose liquid. One of the great things about 2-26, when you push the nozzile slowly, it comes out in a foam, and seems to penetrate and stick to materials with ease. It says its plastic safe, and improves electrical properties right on the can. I keep thinking, or dreaming, of an old WD-40 can with assemblies on the can including TV tuners. Am I wrong? I often coat entire electronics boards with WD-40 after I wash them with water I actually prefer Bullfrog electrical cleaner and corrosion blocker with VCI's for this purpose. It also smell sweet like maple syrup, but not sticky. I just read low odor on the can. Thats a lie. greg |
#40
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rusty transformers
On Jul 2, 12:53*am, "Phil Allison" wrote:
"bigwig = bigwank " WD 40. Well its the best selling bodge-tastic do it all nothingness that exists. *** Funny how so many folk find it so useful - *then. Anyway as for WD 40 I am certain it contains silicone.. ** It says right on the can " No Silicone. No kerosene ". *But *****wits like YOU can never be convinced of anything. * *.... *Phil You are a complete ****ing ****. It may well say that it has no silicone but we were not allowed to use it in the clean room because it may well do. Anyway it certainly doesnt say no kerosene, you complete ****in retard open your remaining eye or are you using them both to watch your self wank to your own cleverness. Prick. |
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