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#41
Posted to rec.audio.tubes
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rusty transformers
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#42
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rusty transformers [silicone in WD-40]
"GregS" wrote in message
... In article , "Dr. Barry L. Ornitz" wrote: 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/ Yes, I have used Stabilant 22 before and found it to work well in certain applications. I glanced over the application notes and such they publish and found they were very careful not to say anything like what they sent you in your letter. By not publishing such incorrect information about WD-40 publicly, they are less likely to be sued. But what a salesman tells you in private is a different matter entirely. Much of the promotion of Stabilant 22 is hype. This makes me suspect his comments even more. Neither WD-40 nor Stabilant 22 is a wonder cure-all for all ills. Oh, the correct name of the company is D. W. Electrochemicals, Ltd. 73, Barry WA4VZQ |
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#43
Posted to rec.audio.tubes
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rusty transformers
"Patrick Turner" wrote in message
... {lots of stuff snipped throughout} 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. The ideal materials will not harden at all at room temperature, although Glyptal makes a number of alkyds that will air dry or bake. Wattyl Estapol ... 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. It is probably designed to air dry. ....Motor rewinding shop... 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 don't know if Harbor Freight is in Australia, but they are an importer of Chinese tools of "reasonable" quality, not junk but still not professional quality. They sell a venturi pump that runs on compressed air much like in a chemical lab where they use a water driven aspirator. They claim it achieves around 28 inches of mercury vacuum using 4.2 cubic feet per minute of 90 PSI air. It cost around $15 US. It is very difficult to hurt one of these. http://www.harborfreight.com/cpi/cta...emnumber=96677 You don't really need all that much vacuum. It is best if you go through several cycles of vacuum/release/vacuum/release. This will eliminate much of the trapped air and fill the void spaces with resin. You really should avoid boiling the resin. 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. All I can suggest here is to find another shop with a worker who is into hollow state audio. 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. Adherence to polyethylene and polyester is going to be a problem. Polyethylene (polythene) does not have a high service temperature anyway. High density polyethylene has a heat deflection temperature of slightly less than 80 C and a Vicat softening point of 125 C. Polyethylene terephthalate (polyester) has a heat deflection temperature of approximately 115 C and a maximum service temperature of 110 C. The only way you are going to get a strong bond to PE or PET is to surface oxidize the plastics with a corona dischange. 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. I gave this a lot of thought today and I think I may have something useful for you to consider. Have you thought about a two-part, condensation-polymerization-cure silicone? General Electric and Dow make a range of materials with differing pot lives, viscosity, service temperature, etc. Most of these will cure at room temperature, and they will bond to PE and PET better than most materials will. The end product is elastomeric (rubber like) which should be excellent in suppressing vibration. Many have service temperatures over 200 C after curing. You can get cures from a few minutes to several hours. There are low viscosity liquids for potting to thixotropic gels that flow when painted on, but gel when the shear is stopped thereby not running on vertical surfaces. I suggest looking for RTV (room temperature vulcanizing) silicones on the Internet. GE and Dow make scores of varieties so make a list of the necessary properties, and the preferred properties and contact the maufacturers. It might be a good idea to request brochures and datasheets before you make your selection. If you don't act like Phil, you might even get some free samples! 73, Barry WA4VZQ |
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#44
Posted to rec.audio.tubes
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rusty transformers
On Jul 1, 9:46*pm, Patrick Turner wrote:
Engineer wrote: (snip) 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.- Hide quoted text - - Show quoted text - Patrick, thanks for the usual thoughtful reply. Cheers, Roger |
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#45
Posted to rec.audio.tubes
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rusty transformers
"Dr. Barry L. Ornitz" wrote: "Patrick Turner" wrote in message ... {lots of stuff snipped throughout} 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. The ideal materials will not harden at all at room temperature, although Glyptal makes a number of alkyds that will air dry or bake. Wattyl Estapol ... 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. It is probably designed to air dry. It is designed to air dry. Its just a polyurethane one pot varnish. I have used it in transformers. If you heat it and try forcing it into a tranny with atmospheric pressure after pulling a vacuum, then what you have left over tends to gel and you can't use that again. If there isnt one damnn problem, there is another! ...Motor rewinding shop... 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 don't know if Harbor Freight is in Australia, but they are an importer of Chinese tools of "reasonable" quality, not junk but still not professional quality. They sell a venturi pump that runs on compressed air much like in a chemical lab where they use a water driven aspirator. They claim it achieves around 28 inches of mercury vacuum using 4.2 cubic feet per minute of 90 PSI air. It cost around $15 US. It is very difficult to hurt one of these. http://www.harborfreight.com/cpi/cta...emnumber=96677 You don't really need all that much vacuum. It is best if you go through several cycles of vacuum/release/vacuum/release. This will eliminate much of the trapped air and fill the void spaces with resin. You really should avoid boiling the resin. The device you have referred me to needs a compressor to work it but U have one so maybe the device would be quite good for me. 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. All I can suggest here is to find another shop with a worker who is into hollow state audio. I live in asmall city of 300,000 ppl where the number of trades people into tube craft is zero apart from myself. The number of ppl in the whole of Oz with population 21 millions is about 3 maybe, and I could never ever find them. 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. Adherence to polyethylene and polyester is going to be a problem. Polyethylene (polythene) does not have a high service temperature anyway. High density polyethylene has a heat deflection temperature of slightly less than 80 C and a Vicat softening point of 125 C. Polyethylene terephthalate (polyester) has a heat deflection temperature of approximately 115 C and a maximum service temperature of 110 C. The only way you are going to get a strong bond to PE or PET is to surface oxidize the plastics with a corona dischange. Goodness me, looks like nothing can be made to easily work then. Many tranny makers use polyester and normal transformer electrical varnish meant for the job. after a vanish job the adhesion isn't perfect to the polyester. But better than no adhesion at all. Seems like the varnish sort of is soft and sticky when hot, and any deformation under heat of the polyester with wire pressure allows varnish to find its way into gaps and when it all cools it all goes fairly hard, and its enough to stop wire movements. I guess the varnish would not stick well to wire enamel, ie, polyester-imide but from what I see the varnish does a good job of solidifying a bunch of wires all couped up in a lump around a core. 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. I gave this a lot of thought today and I think I may have something useful for you to consider. Have you thought about a two-part, condensation-polymerization-cure silicone? General Electric and Dow make a range of materials with differing pot lives, viscosity, service temperature, etc. Most of these will cure at room temperature, and they will bond to PE and PET better than most materials will. The end product is elastomeric (rubber like) which should be excellent in suppressing vibration. Many have service temperatures over 200 C after curing. You can get cures from a few minutes to several hours. There are low viscosity liquids for potting to thixotropic gels that flow when painted on, but gel when the shear is stopped thereby not running on vertical surfaces. I will have to search fr this product. But if only NASA use it, maybe getting a 4 Litre can could cost $3,000, plus freaight and GST! As I mentioned there are self 2 part "potting mixes" but they are terribly expensive. Some have been around for some time. The goop used by Quad to pot the power transformer in the Quad 405 is about the right stuff for sure. But its expensive. It doesn't generate too much heat when it goes off. Maybe no pong, and maybe can withstand a vacuum and has low viscosity when mixed for use. But I though maybe something cheaper coud be around which wasn't normally meant for the job but which would still work OK. I suggest looking for RTV (room temperature vulcanizing) silicones on the Internet. GE and Dow make scores of varieties so make a list of the necessary properties, and the preferred properties and contact the maufacturers. It might be a good idea to request brochures and datasheets before you make your selection. If you don't act like Phil, you might even get some free samples! Have no fear, I have a sense of humour, redeaming charm when required, and tolerance for the stupidity of others and well as for my own stupidity. I doubt any free samples are ever likely to come my way unless I was the CEO of NASA. Then they'd send me a truckload. But as a one man band operatiing an obscure tiny business way across the universe in Oz, I doubt GE or Dow are likely to suspect that if they gave me a free sample an order might follow which would allow them to breathe easy in this economic climate and make it possible for their wives to ask for and receive funding for a kitchen renovation with love and kisses. Munny munny munny, itty maky de world go around yo know! No ******* has given me nothin no time, and nobody gives a **** about anyone else much these days. I'm still smilin'....... Patrick Turner. 73, Barry WA4VZQ |
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#46
Posted to rec.audio.tubes
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rusty transformers [silicone in WD-40]
In article , "Dr. Barry L. Ornitz" wrote:
"GregS" wrote in message ... In article , "Dr. Barry L. Ornitz" wrote: 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/ Yes, I have used Stabilant 22 before and found it to work well in certain applications. I glanced over the application notes and such they publish and found they were very careful not to say anything like what they sent you in your letter. By not publishing such incorrect information about WD-40 publicly, they are less likely to be sued. But what a salesman tells you in private is a different matter entirely. Much of the promotion of Stabilant 22 is hype. This makes me suspect his comments even more. Neither WD-40 nor Stabilant 22 is a wonder cure-all for all ills. Oh, the correct name of the company is D. W. Electrochemicals, Ltd. I bought a new batch of Stabilant when I found it at a more reasonable price than the $55 NAPA price. I'm looking at a can of Techspray Blue Stuff. Heavy. They list the Global warming potential on the can, where nobody really knows any global warming potential facts as to exactly how much it can effect global warming in %. Well anyway, my neighbor just gave me a bucket of food grade Diatomaceous Earth. I know now now how really fine this stuff is. I wondered how they could put it in a cleaner lube and not have problems with contact. That stuff is so fine that the metal is usually a lot more ruff with ridges than what the earth could fill in the gaps and cause problems. I'm wondering if I can add this Diatom stuff to other liquid cleaners. How about some Oleic Acid ? What fun. greg |
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#47
Posted to rec.audio.tubes
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rusty transformers [silicone potting compounmds]
"Patrick Turner" wrote in message
... "Dr. Barry L. Ornitz" wrote: I gave this a lot of thought today and I think I may have something useful for you to consider. Have you thought about a two-part, condensation-polymerization-cure I suggest looking for RTV (room temperature vulcanizing) silicones on the Internet. GE and Dow make scores of varieties so make a list of the necessary properties, and the preferred properties and contact the maufacturers. It might be a good idea to request brochures and datasheets before you make your selection. If you don't act like Phil, you might even get some free samples! Have no fear, I have a sense of humour, redeaming charm when required, and tolerance for the stupidity of others and well as for my own stupidity. I doubt any free samples are ever likely to come my way unless I was the CEO of NASA. Then they'd send me a truckload. But as a one man band operatiing an obscure tiny business way across the universe in Oz, I doubt GE or Dow are likely to suspect that if they gave me a free sample an order might follow which would allow them to breathe easy in this economic climate and make it possible for their wives to ask for and receive funding for a kitchen renovation with love and kisses. Munny munny munny, itty maky de world go around yo know! Yes, NASA has deeppockets. But many silicones are relatively inexpensive. If they can sell 1-part silicones as bathtub caulk for a few dollars, you should be able to find something for your application easily. Many 2-part silicones are used by hobbyists for mold making and such, and these are not expensive. The electrical properties of these silicones are still quite adequate for your application. Most silicones when cured are rated at 450 volts per mil (0.001 inch). Farnell sells silicones as does Allied Electronics (http://www.alliedelec.com/Search/Pro...&MPN=RTV630-1P, then click on the link to their catalog page, http://www.alliedelec.com/Catalog/pf.aspx?FN=1959.pdf - they even have Glyptal). The last time I ordered a 2-part high temperature silicone, I ordered it from Newark Electronics. Even Digi-Key, my personal favorite supplier, carries silicones. Look for potting Silicone compounds and encapsulants on Google and I am sure you will find many suppliers. If you find a reasonably priced product, send me a link to their webpage with specifications. I'll be glad to look over three or four for you and suggest the best ones. Heck, I live in a city of 1006. It was 1005 until I moved here. ALL of my electronic parts are mail order these days except for hamfests. Of course I do have a well-stocked junque box. 73, Barry WA4VZQ |
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#48
Posted to rec.audio.tubes
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rusty transformers [silicone potting compounmds]
"Dr. Barry L. Ornitz" wrote: "Patrick Turner" wrote in message ... "Dr. Barry L. Ornitz" wrote: I gave this a lot of thought today and I think I may have something useful for you to consider. Have you thought about a two-part, condensation-polymerization-cure I suggest looking for RTV (room temperature vulcanizing) silicones on the Internet. GE and Dow make scores of varieties so make a list of the necessary properties, and the preferred properties and contact the maufacturers. It might be a good idea to request brochures and datasheets before you make your selection. If you don't act like Phil, you might even get some free samples! Have no fear, I have a sense of humour, redeaming charm when required, and tolerance for the stupidity of others and well as for my own stupidity. I doubt any free samples are ever likely to come my way unless I was the CEO of NASA. Then they'd send me a truckload. But as a one man band operatiing an obscure tiny business way across the universe in Oz, I doubt GE or Dow are likely to suspect that if they gave me a free sample an order might follow which would allow them to breathe easy in this economic climate and make it possible for their wives to ask for and receive funding for a kitchen renovation with love and kisses. Munny munny munny, itty maky de world go around yo know! Yes, NASA has deeppockets. But many silicones are relatively inexpensive. If they can sell 1-part silicones as bathtub caulk for a few dollars, you should be able to find something for your application easily. Many 2-part silicones are used by hobbyists for mold making and such, and these are not expensive. The electrical properties of these silicones are still quite adequate for your application. Most silicones when cured are rated at 450 volts per mil (0.001 inch). Farnell sells silicones as does Allied Electronics (http://www.alliedelec.com/Search/Pro...&MPN=RTV630-1P, then click on the link to their catalog page, http://www.alliedelec.com/Catalog/pf.aspx?FN=1959.pdf - they even have Glyptal). The last time I ordered a 2-part high temperature silicone, I ordered it from Newark Electronics. Even Digi-Key, my personal favorite supplier, carries silicones. Look for potting Silicone compounds and encapsulants on Google and I am sure you will find many suppliers. If you find a reasonably priced product, send me a link to their webpage with specifications. I'll be glad to look over three or four for you and suggest the best ones. Heck, I live in a city of 1006. It was 1005 until I moved here. ALL of my electronic parts are mail order these days except for hamfests. Of course I do have a well-stocked junque box. 73, Barry WA4VZQ I will check all that out. Whatever I use in an OPT needs to be low dielectric constant so it doesn't much increase the capacitances. PT would be good with something which is rubbery rather than hard plastic. Just what I use depends on its viscosity and ease of use, cost, toxicity, and ease of curing. Many thanks. Patrick Turner. |
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#49
Posted to rec.audio.tubes
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rusty transformers [silicone potting compounmds]
"Patrick Turner" wrote in message
... Whatever I use in an OPT needs to be low dielectric constant so it doesn't much increase the capacitances. The dielectric constant of silicone polymers is usually between 2.8 and 3.3 depending on the particular polymer. Dow and GE publish this information on their silicones. PT would be good with something which is rubbery rather than hard plastic. Silicone polymers are considered rubbery. Shore hardness (a standardized physical test) does vary somewhat on the silicone composition. Just what I use depends on its viscosity and ease of use, cost, toxicity, and ease of curing. RTV means room temperature vulcanizing. RTV silicones cure at room temperature, usually within 8 to 24 hours. They cure faster at elevated temperatures, and,once cured, can withstand temperatures up to 200 C. Viscosities vary considerably with composition. Some are as low as 15 Poise and some are as high as 1500 Poise. A simple selection chart can be found at http://www.mgchemicals.com/downloads...uide0205-2.pdf, Toxicity information is also readily available on the Internet. This varies considerably with the particular silicone chosen. In general, silicones are safe to use if regular industrial safety precautions are taken. Many thanks. Patrick Turner. I am glad I could help. Making your own electronic components is a nearly dead art with most hobbyists. Restoration of older radios and other vacuum tube equipment often requires this skill. I enjoy doing this myself so it is good to see the skill in others too. Barry |
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#50
Posted to rec.audio.tubes
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rusty transformers [silicone potting compounmds]
In article , "Dr. Barry L. Ornitz" wrote:
"Patrick Turner" wrote in message ... Whatever I use in an OPT needs to be low dielectric constant so it doesn't much increase the capacitances. The dielectric constant of silicone polymers is usually between 2.8 and 3.3 depending on the particular polymer. Dow and GE publish this information on their silicones. PT would be good with something which is rubbery rather than hard plastic. Silicone polymers are considered rubbery. Shore hardness (a standardized physical test) does vary somewhat on the silicone composition. Just what I use depends on its viscosity and ease of use, cost, toxicity, and ease of curing. RTV means room temperature vulcanizing. RTV silicones cure at room temperature, usually within 8 to 24 hours. They cure faster at elevated temperatures, and,once cured, can withstand temperatures up to 200 C. Viscosities vary considerably with composition. Some are as low as 15 Poise and some are as high as 1500 Poise. A simple selection chart can be found at http://www.mgchemicals.com/downloads...uide0205-2.pdf, Toxicity information is also readily available on the Internet. This varies considerably with the particular silicone chosen. In general, silicones are safe to use if regular industrial safety precautions are taken. Many thanks. Patrick Turner. I am glad I could help. Making your own electronic components is a nearly dead art with most hobbyists. Restoration of older radios and other vacuum tube equipment often requires this skill. I enjoy doing this myself so it is good to see the skill in others too. I have used Sylgard, and am holding an unused, kind of like a big syringe, in my hand. Seems to run about $50 now for 250 ml. Small samples can be had by Dow. I don't remember how runny it is, but I don't think it will seep into all areas. In looking at the kit, it would seem there is some kind of tool for the dual syringe thing to be put into. Like a gun. There was a silicon rtv which I bought at the auto store long ago, very runny designed for windshields. I have not seen any of that lately. Handy stuff. I usually thin down the rtv with alcohol when I want to get it runny, or just use alcohol to smooth down the finish. I can even apply it with an acid brush. If you did a little at a time, you could build up thickness. However, I find it sticks better to itself if you degrease it. Caution, citrus degreasers, make a greasy mess. Like oil. greg |
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