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Restoring a Sherwood S-5000



 
 
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  #31  
Old January 18th 15, 07:45 PM posted to rec.audio.tubes
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Posts: 1
Default Restoring a Sherwood S-5000

On Friday, October 10, 2014 at 3:02:00 PM UTC-5, hugeshows wrote:
> On Wednesday, July 23, 2014 11:49:00 PM UTC-4, wrote:
> > "C24/B - 250v 204v"
> >
> >
> >
> > Hi, did you figure out why you measured 46v below what the schematic reads?
> >
> >
> >
> > Sorry if I missed the explanation but I only see how you resolved the bias voltage supply.
> >
> >
> >
> > Cheers!

>
> Sorry folks, haven't checked in here in a while. I'll take another look this weekend and see if I can answer some of these questions.
>
> Cheers!



Hello. This is a great write up on the 5000. I just picked up one of these on Eaby. Its the S-5000 20 + 20 Stereo Amplifier. Its the unit that has the 4 pushbuttons on the left front panel for phone manipulation. The tube compliments are 5 Sovtek 12AX7(1208), 2 RCA 7199, I cant make out what the output tubes are as the ink has been worn off but what is left of the lettering is 6BQ5 and 065-090 and the word organ. I would like to know if I should replace the phone tubes(the two at the far left) with something else, I primarily listen to the phone input. Also would I benefit from different 7199's or output tubes. Much thanks for your advise.
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  #32  
Old February 12th 15, 04:17 AM posted to rec.audio.tubes
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Default Restoring a Sherwood S-5000

Just wondering if these can be used as preamplifiers? Do they have a preamp out? Specifically the s5000ii. Thanks
  #33  
Old August 2nd 15, 07:33 PM posted to rec.audio.tubes
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Posts: 3
Default PWR transformer for a Sherwood S-5000

On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
> Hello all,
>
> One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.
>
> The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.
>
> The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.
>
> In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.
>
> If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.
>
> Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.
>
> For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.
>
> This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.
>
> Feel free to ask away as I prepare some pics and schematics to get this started.
>
>
> -forkinthesocket


New guy. Desperate for help.
The post about restoring the Sherwood S-5000 caught my eye.
I sure would like to do that, but....
My poor amp has a blown power transformer.
Any ideas on a replacement?
  #34  
Old August 4th 15, 11:58 AM posted to rec.audio.tubes
Peter Wieck
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Posts: 2,418
Default PWR transformer for a Sherwood S-5000

On Sunday, August 2, 2015 at 2:33:49 PM UTC-4, wrote:

> New guy. Desperate for help.
> The post about restoring the Sherwood S-5000 caught my eye.
> I sure would like to do that, but....
> My poor amp has a blown power transformer.
> Any ideas on a replacement?


It would be helpful to know the make/model/condition of your amp. And what specific part of the PT that is blown, if known. For instance, if the primary winding is bad, then it is pretty much hopeless, as with the B+ winding(s). But if it is a filament winding (6.3V or 5V) you may be able to install a separate filament transformer.

If you have any of several Dynaco products, OEM replacements are still being made, less so for other brands, but still out there.

And, of course, are the usual transformer builders such as Hammond and others that have both a range of replacement transformers and will even make one for you at a reasonable price, especially if it is already templated.

Lastly, there are transformer rewinders out there that do a fairly credible job with units that may not be otherwise available. Just look up "Transformer Rewinding Service" and take your pick.

Best of luck with it.

Peter Wieck
Melrose Park, PA
  #35  
Old August 5th 15, 10:26 PM posted to rec.audio.tubes
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Posts: 3
Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
> Hello all,
>
> One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.
>
> The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.
>
> The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.
>
> In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.
>
> If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.
>
> Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.
>
> For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.
>
> This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.
>
> Feel free to ask away as I prepare some pics and schematics to get this started.
>
>
> -forkinthesocket


Yea, I did miss a few details, I guess. I wanted to see if I could work the system before I dove in.
I had read several posts about how good the Sherwood S-5000 is so I bought my own. Nice cosmetic condition but a blown PWR transformer. Primary side..

Main problem with getting a non-stock replacement is the tight fit and the 30VDC filament and bias voltage needed.
The numbers on the transformer are B922J3-5 and A949005.
If I can't find an original replacement, I will have to look at the rewinding option. Seem that would be a bit costly. I'm in no hurry, so I will wait a while.
  #36  
Old August 8th 15, 12:29 AM posted to rec.audio.tubes
MarkS[_3_]
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Posts: 4
Default Restoring a Sherwood S-5000

On Wednesday, August 5, 2015 at 5:26:31 PM UTC-4, wrote:
> On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
> > Hello all,
> >
> > One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.
> >
> > The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.
> >
> > The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.
> >
> > In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.
> >
> > If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.
> >
> > Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.
> >
> > For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.
> >
> > This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.
> >
> > Feel free to ask away as I prepare some pics and schematics to get this started.
> >
> >
> > -forkinthesocket

>
> Yea, I did miss a few details, I guess. I wanted to see if I could work the system before I dove in.
> I had read several posts about how good the Sherwood S-5000 is so I bought my own. Nice cosmetic condition but a blown PWR transformer. Primary side.
>
> Main problem with getting a non-stock replacement is the tight fit and the 30VDC filament and bias voltage needed.
> The numbers on the transformer are B922J3-5 and A949005.
> If I can't find an original replacement, I will have to look at the rewinding option. Seem that would be a bit costly. I'm in no hurry, so I will wait a while.


You can check out these guys-

http://www.heyboertransformers.com/tubeamps.shtml

They made a custom power transformer for my LK72 Scott several years ago at a very reasonable price. They may know what specs you need already or you'll have to draw up a spec.

BR's,

Mark
  #37  
Old August 13th 15, 09:04 PM posted to rec.audio.tubes
[email protected]
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Posts: 3
Default Restoring a Sherwood S-5000

On Sunday, January 12, 2014 at 1:52:54 PM UTC-6, hugeshows wrote:
> Hello all,
>
> One of my favorite tube amps has to be the Sherwood S-5000. It's a little gem of an integrated amp that is quite easily underestimated. Most people would put it in the same class as a Scott 299, also a 6BQ5 amp, although the Sherwood is really a 7189 amp, and actually uses the higher plate voltage possible with the 7189. It also has larger output transformers, and manages to put out 24w RMS per channel.
>
> The pre-amp section, despite having dated ideas about tone control and Fletcher-Munson curves (thankfully switchable) maintains a very neutral and open sound. The bass and treble knobs are actually usable and helpful at times, and don't have some insane Q that belies their center frequency. The phono section is startlingly good so long as the original Telefunken 12AX7s are occupying the two sockets in the phono section. There are a handful of other tubes that can work there as well, but filament hum and microphonics plague any U.S. made 12AX7 or 7025 I have ever tried in this amp, shield or no.
>
> The use of 7199 tubes as the phase splitter/driver tubes is somewhat unfortunate since they are hard to obtain these days. The upshot is that they seem to last a very long time in this circuit, and they sound quite good. Some have attempted to use 6GH8A in this position, or modern Russian 7199 that are actually re-pinned 6GH8A, and I would strongly discourage that. They don't sound right at all. Just ask the ST-70 crowd. You'd have to modify the circuit, and I think that in this case, that's just daft. The 7199 last too long and sound too good to make that a useful mod, IMHO.
>
> In this thread, I will be going over the basic steps of reviving a Sherwood S-5000 as I rebuild yet another one of these beauties. This is more or less your standard re-cap job, plus replacing the selenium rectifier in the bias supply. There are however some things that are specific to this amp, little tricks for dealing with the tight chassis space, and other stuff too. The way capacitors are mounted in this amp is a real pain. It uses twist-lock can caps, one of which is mounted at a 35 degree angle.
>
> If -YOU- have an S-5000 or S-4400 and you have any questions about it, please feel free to ask away and I will cover the topic in this thread. I've dealt with just about everything there is do deal with on these amps, as this will be the 6th one I've restored. The S-5000II is a totally different beast using 7591s, and I will not be covering that amp here.
>
> Still trying to figure out where I will post pics and schematics so I can post links here, so give me a little while on that.
>
> For those of you exclusively into DIY, the S-5000 circuit is a very cool and sweet sounding 7189 amp. It's the only amp I've seen that gets 24 watts out of a pair of 7189s. I've made one using the Triode Electronics ST-70 board as a front-end and the result was so good that it sold for $1000 despite being a prototype and not terribly well built. It was in a Hammond box as I recall, but I did engine turn the top at least. So we can also discuss DIY around this circuit in this thread if anyone wants.
>
> This is my favorite vintage amp of all time, so I can talk about it endlessly without getting bored.
>
> Feel free to ask away as I prepare some pics and schematics to get this started.
>
>
> -forkinthesocket


I just checked. It would be $120 plus shipping? Not too bad.
  #38  
Old September 6th 15, 08:00 PM posted to rec.audio.tubes
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Posts: 2
Default Restoring a Sherwood S-5000

Dear All,

I am seeking practical advice, further I am not a knowledgeable electronics guy, tube or otherwise -- to say the least.

A few years ago I was fortunate enough to find and purchase a Sherwood S5000 II; I am into 50s cars and hot rods and just wanted the aesthetics and joy of tube hi-fi ownership. A Sherwood expert here in the KC area completely refurbished the unit with no shortcuts taken. He only charged me for parts, not labor. Until recently my 5000S has provided excellent service for about two years of moderate use.

A couple of months ago the amp began generating some sort of signal spike that resulted in conspicuously loud crackling noise through the speakers. Since I do not use the amp's metal dust cover I was able to observe bright light flashes emitting from one of the four identical "power" (??) vacuum tubes situated at the rear of the amp.

I pulled out the offending vacuum tube, which unlike its counterparts showed discoloration at the "top" of the glass, presumably plasma vapor deposited metal.

The tubes, I now know, are Russian built electro-harmonic 7591A units. I was unable to contact the fellow who refurbished the S5000 II, so I went online and found multiple vendors for the Russian 7591A tubes. I bought a "set" of four, which I received and which appear identical to the my "original" electro-harmonic tubes.

Now my reason for this query: The cross-sectional diameter of the electro-harmonic 7591A units are too large to fit properly in the Sherwood sockets. What gives?

A brief search online suggests to this novice that these modern aftermarket tubes are (duh) fatter than the original electron tubes. I see mention of aftermarket pin adapters so that tubes with similar electronic properties, but different pin patterns, can be substituted. Does such an adapter exist for my Sherwood sockets?

Alternatively, because the shape of the electro-harmonic 7591A glass housings are slightly tapered cones (thinner toward the top) if one had a half-inch tall adapter 7591-to-7591 the Russian tubes would then fit without side-to-side glass contact, assuming I alternated adapters at every other socket position. Does such an adapter exist?

As it stands right now the four "new" tubes contact their respective neighbor, with the outermost (2) tubes unable to fit squarely into their socket. Am I correct in thinking that such glass-to-glass contact is not good for electron tube lifetime? This mechanical interference has to be putting stress on the glass, right? Should I pay big bucks for NOS tubes that fit properly?

Any advise or suggestions will be sincerely appreciated. I guess it's not the end of the world if I have to replace tubes often, but the present arrangement seems pretty lame to me.

Thanks,

Charlie
  #39  
Old September 7th 15, 01:45 PM posted to rec.audio.tubes
MarkS[_3_]
external usenet poster
 
Posts: 4
Default Restoring a Sherwood S-5000

On Sunday, September 6, 2015 at 3:00:42 PM UTC-4, wrote:
> Dear All,
>
> I am seeking practical advice, further I am not a knowledgeable electronics guy, tube or otherwise -- to say the least.
>
> A few years ago I was fortunate enough to find and purchase a Sherwood S5000 II; I am into 50s cars and hot rods and just wanted the aesthetics and joy of tube hi-fi ownership. A Sherwood expert here in the KC area completely refurbished the unit with no shortcuts taken. He only charged me for parts, not labor. Until recently my 5000S has provided excellent service for about two years of moderate use.
>
> A couple of months ago the amp began generating some sort of signal spike that resulted in conspicuously loud crackling noise through the speakers. Since I do not use the amp's metal dust cover I was able to observe bright light flashes emitting from one of the four identical "power" (??) vacuum tubes situated at the rear of the amp.
>
> I pulled out the offending vacuum tube, which unlike its counterparts showed discoloration at the "top" of the glass, presumably plasma vapor deposited metal.
>
> The tubes, I now know, are Russian built electro-harmonic 7591A units. I was unable to contact the fellow who refurbished the S5000 II, so I went online and found multiple vendors for the Russian 7591A tubes. I bought a "set" of four, which I received and which appear identical to the my "original" electro-harmonic tubes.
>
> Now my reason for this query: The cross-sectional diameter of the electro-harmonic 7591A units are too large to fit properly in the Sherwood sockets.. What gives?
>
> A brief search online suggests to this novice that these modern aftermarket tubes are (duh) fatter than the original electron tubes. I see mention of aftermarket pin adapters so that tubes with similar electronic properties, but different pin patterns, can be substituted. Does such an adapter exist for my Sherwood sockets?
>
> Alternatively, because the shape of the electro-harmonic 7591A glass housings are slightly tapered cones (thinner toward the top) if one had a half-inch tall adapter 7591-to-7591 the Russian tubes would then fit without side-to-side glass contact, assuming I alternated adapters at every other socket position. Does such an adapter exist?
>
> As it stands right now the four "new" tubes contact their respective neighbor, with the outermost (2) tubes unable to fit squarely into their socket.. Am I correct in thinking that such glass-to-glass contact is not good for electron tube lifetime? This mechanical interference has to be putting stress on the glass, right? Should I pay big bucks for NOS tubes that fit properly?
>
> Any advise or suggestions will be sincerely appreciated. I guess it's not the end of the world if I have to replace tubes often, but the present arrangement seems pretty lame to me.
>
> Thanks,
>
> Charlie


Hi Charlie,

Glass to glass contact is not great idea. Beyond NOS 7591A's, there are other options. Right up front, I do not have any personal experience with the new production 7591A's, just NOS- but these days, that can be a crap shoot as well. Anyway, JJ makes a 7591A that is the same diameter as NOS so they should fit better. Also, the same company that makes the Electro Harmonix 7591A's (New Sensor) also released a so called "re-issue" Tung Sol 7591A. I believe these are the same diameter as the JJ / NOS but appear to be 2x the price of JJ's. If I were going to new production, I would probably go with the Tung Sols.
The spacer idea is neat but you may have to make those yourself. Use a tube socket and tube base. There was a time when the 6GM5 was an NOS 7591A alternative but had a different base so an adapter was needed. The price of a 6GM5 is up there now an NOS 7591A anyway so the climb might not be worth the view.

BR's,

Mark
  #40  
Old September 10th 15, 08:14 PM posted to rec.audio.tubes
[email protected]
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Posts: 2
Default Restoring a Sherwood S-5000

On Monday, September 7, 2015 at 7:45:24 AM UTC-5, MarkS wrote:
> On Sunday, September 6, 2015 at 3:00:42 PM UTC-4, wrote:
> > Dear All,
> >
> > I am seeking practical advice, further I am not a knowledgeable electronics guy, tube or otherwise -- to say the least.
> >
> > A few years ago I was fortunate enough to find and purchase a Sherwood S5000 II; I am into 50s cars and hot rods and just wanted the aesthetics and joy of tube hi-fi ownership. A Sherwood expert here in the KC area completely refurbished the unit with no shortcuts taken. He only charged me for parts, not labor. Until recently my 5000S has provided excellent service for about two years of moderate use.
> >
> > A couple of months ago the amp began generating some sort of signal spike that resulted in conspicuously loud crackling noise through the speakers.. Since I do not use the amp's metal dust cover I was able to observe bright light flashes emitting from one of the four identical "power" (??) vacuum tubes situated at the rear of the amp.
> >
> > I pulled out the offending vacuum tube, which unlike its counterparts showed discoloration at the "top" of the glass, presumably plasma vapor deposited metal.
> >
> > The tubes, I now know, are Russian built electro-harmonic 7591A units. I was unable to contact the fellow who refurbished the S5000 II, so I went online and found multiple vendors for the Russian 7591A tubes. I bought a "set" of four, which I received and which appear identical to the my "original" electro-harmonic tubes.
> >
> > Now my reason for this query: The cross-sectional diameter of the electro-harmonic 7591A units are too large to fit properly in the Sherwood sockets. What gives?
> >
> > A brief search online suggests to this novice that these modern aftermarket tubes are (duh) fatter than the original electron tubes. I see mention of aftermarket pin adapters so that tubes with similar electronic properties, but different pin patterns, can be substituted. Does such an adapter exist for my Sherwood sockets?
> >
> > Alternatively, because the shape of the electro-harmonic 7591A glass housings are slightly tapered cones (thinner toward the top) if one had a half-inch tall adapter 7591-to-7591 the Russian tubes would then fit without side-to-side glass contact, assuming I alternated adapters at every other socket position. Does such an adapter exist?
> >
> > As it stands right now the four "new" tubes contact their respective neighbor, with the outermost (2) tubes unable to fit squarely into their socket. Am I correct in thinking that such glass-to-glass contact is not good for electron tube lifetime? This mechanical interference has to be putting stress on the glass, right? Should I pay big bucks for NOS tubes that fit properly?
> >
> > Any advise or suggestions will be sincerely appreciated. I guess it's not the end of the world if I have to replace tubes often, but the present arrangement seems pretty lame to me.
> >
> > Thanks,
> >
> > Charlie

>
> Hi Charlie,
>
> Glass to glass contact is not great idea. Beyond NOS 7591A's, there are other options. Right up front, I do not have any personal experience with the new production 7591A's, just NOS- but these days, that can be a crap shoot as well. Anyway, JJ makes a 7591A that is the same diameter as NOS so they should fit better. Also, the same company that makes the Electro Harmonix 7591A's (New Sensor) also released a so called "re-issue" Tung Sol 7591A. I believe these are the same diameter as the JJ / NOS but appear to be 2x the price of JJ's. If I were going to new production, I would probably go with the Tung Sols.
> The spacer idea is neat but you may have to make those yourself. Use a tube socket and tube base. There was a time when the 6GM5 was an NOS 7591A alternative but had a different base so an adapter was needed. The price of a 6GM5 is up there now an NOS 7591A anyway so the climb might not be worth the view.
>
> BR's,
>
> Mark


THANKS MARK

Just the focused spot-on information I needed. If you ever need any info old hot rods give me a holler.

Charlie
 




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