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Ping Michael Samra, Sherwood questions..

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Posted on October 25, 2014 at 09:49:53
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005



Hi, Michael (and anyone else who is watching!), picked up a Sherwood S-5000 integrated at a local hamfest, something I have been on the hunt for with all the love for the Sherwood out there. After buying it and looking it over, I have some questions. First, it had an umbilical cord coming out of a hole in the upper left adjacent the front mounted capacitor that is obviously not original so I removed that. While removing that cord I noticed that the power transformer did not quite fit the original mounting holes which leads me to suspect that the power tranny may not be original, it does not have a metal stamped number on it but does have an ink stamp number (8387). I am also missing a knob, any suggestions on where to get one? This looks to be the second gen 6BQ5 model... thanks!

 

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RE: Ping Michael Samra, Sherwood questions.., posted on October 25, 2014 at 10:03:11
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Randy
THe transformer that's in there probably came out of a Scott or another integrated amp with similar tube layout.Very few have those transformers laying around because they seldom ever failed. You do need a cover over the controls for shielding but you can make one if you have to.I have a knob but if you want a power trafo of perfect fit,try Ebay or let Heyboer wind one for you.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 25, 2014 at 11:04:31
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Michael, what would you want for the knob? Its the loudness knob. BTW, the face panel of this Sherwood is pretty dirty, kind of grimy that really shows off against the white face panel. I tried at first using a Q-tip with Windex, but that also seems to remove the black lettering. I next tried some baby wipes, that works a little but the dirty white is still there. Lastly, I am guessing I should replace the PS caps and try to power this up with good tubes and see how my voltages are vis-a-vis the schematic to see if the replacement tranny is working correctly, or get Heyboer to wind a replacement along the lines of the 1st gen Sherwood that had the larger power transformer, yes? thanks!

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 25, 2014 at 12:31:57
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 Nothing for the knob..Email me an address.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 25, 2014 at 13:40:54
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Michael, it's gkargreen@verizon.net. BTW, I have been trying to clean the front panel, found that Simple Green Extreme works pretty good but it is also removing a layer of the paint so I have to go slow so as not to remove too much of the lettering. Once I am able to get this up and operational, I would probably like to ask further questions about the transformer, whether the one in my unit is up to snuff, thanks, Randy

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 25, 2014 at 17:10:55
Michael Samra
Dealer

Posts: 36118
Location: saginaw michigan
Joined: January 30, 2005
 I only use the simple green on the knobs and I dilute it before I use it.
"For every complex problem there is an answer that is clear, simple, and wrong" H. L. Mencken

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 29, 2014 at 14:44:36
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hello,

Glad to see you got an S-5000, it's one hell of an amp and most people dismiss it because its an early integrated unit. Big mistake. This amp is VERY good.

It's a shame about the power transformer. The new one may or may not be up to the task, I'd start by measuring your B+ voltage. If you're not in the 425v region there, the amp will probably have any real oomph. If that transformer came out of a 6BQ5 integrated, chances are the B+ voltage will be quite a bit lower.

Usually, the only time these Sherwood transformers fail is if there is something wrong with the circuit causing a prolonged over-current condition. Leaky caps, dodgy bias circuit mods, and the like are worth looking for. There was likely a reason that the original tranny blew.

If it's got your voltages where they need to be, doesn't get excessively hot in operation, then you might be fine. I am really worried that this tranny won't give you all the voltage you want on the B+ side though.

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 29, 2014 at 15:11:08
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Sherwood, do you know if the tranny from a S-1000 would work in the S-5000 short body I have? Was thinking about using one from the S-1000 as they look to have similar tube complements... thanks!

 

RE: Ping Michael Samra, Sherwood questions.., posted on October 29, 2014 at 16:14:56
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hi,

I suppose it's possible an S-1000 transformer would work, though there were different versions with different tube compliments. I seem to recall, though not 100% sure that the 6BQ5 version of the S-1000 did not run the tubes as hard as the S-5000 voltage-wise, but I will look into that as I think I have the SAMS photofact somewhere. What variant of the S-1000 do you have?

Anyway, measure your voltage on that power transformer you have in there, it might be OK, I just have no way of knowing.


Cheers,

SF

 

RE: The Monster Amp, posted on October 29, 2014 at 17:06:43
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hi again,

The S-1000 II transformer is listed with these specs in SAMs

Pri: 117v @.87A
Sec1: 740VCT @.080A
Sec2: 5v @1.9A
Sec3: 6.3VCT @3.6A
Sec4: 52VCT @.15A

The S-5000 is listed as:

Pri: 117v @ 1.05A
Sec 1: 720VCT @.100A
Sec 2: 5V @ 2A
Sec 3: 60VCT @ .150A (this is the OLD S-5000, the newer ones like yours have no center tap here, and are grounded differently!)
Sec 4: 6.3VCT @ 5.2A

So, it looks like the voltage is actually higher on the S-1000 II, but the windings don't have the current overhead. The .080 vs .100 difference doesn't bother me as much as the 1.6A difference on the filaments. The question is: Did SAM's merely calculate the current draws, and spec the trannies that way, or are these actual transformer specs?

The S-5000 I have has a B922J3 transformer in it, which is the same one SAM's lists. This is kind of odd, because the photofact shows the earlier S-5000, which has a larger power transformer than the later version, which you have, and which I just looked at to confirm trannie numbers....

S-1000 II has a B922B2 transformer according to SAM's

Cheers,

SF

 

RE: The Monster Amp, posted on October 29, 2014 at 17:31:22
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Sherwood, I will be taking a hard look at the replacement that is in there, of course I don't know what the current is in the replacement, so that is a crapshoot, heck, I don't even know where the replacement came from! Mikey recommended having Heyboer wind a new one, so that is an option as well, but the S1000 II is a consideration, thanks!

 

RE: The Monster Amp, posted on October 29, 2014 at 17:35:57
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 So, more thoughts....

First off, we don't know what the power transformer is in there, and who knows, maybe it's up to the task. One thing I notice however, is that the Shwerwood power trannies always have a copper shield on them, this one does not. Who knows how critical that is in the design of the amp (or not).

Let's start with basics. Let's assume that if it hasn't burned out that it can handle the filament currents. Pull the rectifier and measure (with an appropriately rated meter!!) the unloaded AC to the rectifier. It should be well north of 700v, perhaps closer to 800! I just measured an S-360 last night and it was like 768 unloaded. If you're in that region, we might be able to make the thing work correctly with that transformer. Sure it's a bit ugly and doesn't quite fit, but hey, unless the rest of the amp is a museum piece, why bother fixing adequate? If you ever want a perfect S-5000, you're going to want to lurk and find one of the older ones anyway. Those power trannies don't even get warm, while the newer ones get downright hot.

Anywho, let's take a look at your unloaded HV~ and see if it's in the ball park. Then, if your caps are good enough for testing purposes, let's see what your DC looks like after the first and second filter stages. I can show you how to modify the bias on this amp to get your current happy even if you're a few volts on either side, but you really need your B+ to be north of 400v for this amp to sing.

Take a (careful, one handed) measurement of your AC and let me and Mike know what's up.

 

a bit more info on this unit..., posted on October 29, 2014 at 19:07:49
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 well, I really have to wonder about this, one thing I had noted was this wire cable arrangement that is a kludge I removed, upon further inspection, the bias supply is not present! The bias must have been supplied via the cable kludge, the selenium rectifier is missing with nothing in its place, the replacement tranny has wiring to the plates and filament, the rest of the wires on the secondary (except for a couple of tranny cts) are wrapped up, I guess the replacement did not have the needed bias winding, this is turning into a lot more work than I expected...

 

RE: The Monster Amp, posted on October 30, 2014 at 12:04:06
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 Sherwood, I don't think the S-1000 II tranny has the proper fil winding rating, I did a count up and the min current would be around 4.2 A for all the 6 V tubes, 3.6 A is too low... Now the S-5000 I am not sure of how the 12AX7 are connected, if they are in series the current draw is lower than in parallel, which I suspect they are in, do you know how the fils are strung? thanks

 

RE: The Monster Amp, posted on October 30, 2014 at 12:23:47
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hi,

Yes I do know how the fils are done, it's a little odd actually.

The fils for the 7189, 7199, and the last 3 of the 12AX7s is all AC off the main fil winding. The two 12AX7s in the phono section are filtered DC, which is derived from the bias supply circuit!

The S-1000 II uses only 4 preamp tubes total, 12AX7s and a 6BA8 if I recall correctly. No 7199s.

 

RE: The Monster Amp, posted on October 30, 2014 at 12:37:23
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, what I meant was are the 12AX7 in parallel with each other, or series? This affects the total filament current that the power tranny needs to provide...

 

RE: The Monster Amp, posted on October 30, 2014 at 12:44:23
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 All the AC (except recifier of course) fils are parallel, the two DC fils for the phono stage are serial I believe. I can double-check when I get home, but I am 100% sure about the AC fils, and 95% sure about the DC.


Cheers.

-SF

 

RE: The Monster Amp, posted on October 30, 2014 at 12:58:13
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, that would give a total fil draw of 5.2 A that you noted on the Sams, the fil. current on the S-1000 II I calculate to be between 4.1-4.4, depending on how the 12AX7s are wired, so I am looking at a difference of around 1 amp at this point. Would that be a deal breaker for the S-1000 tranny?

 

RE: The Monster Amp, posted on October 30, 2014 at 13:17:52
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 I dunno, personally I think that it might wind up burning out the filament winding, or result in the power transformer getting hot, or dropping the overall filament voltage too much. I'm not sure I'd risk it. Especially because a second S-1000 would give you a very worthy stereo pair at 36WPC.

I have an S-5000 parts unit with a dead power transformer. If you decide to go the re-wind route, it's yours for the shipping. One catch is that it's in storage at my friend's house in Georgia, but I could get him to pull it and send it your way no problem.


Cheers,

SF

 

thanks, Sherwood, BTW..., posted on October 31, 2014 at 12:36:44
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 do you have the specifications on the ver.1 S-5000? I am thinking that if I can get Heyboer to wind a power tranny that it should be best to have the early, heavier tranny wound, rather than the older, smaller tranny. Will the ver. 1 tranny fit the short S-5000? Als, yes, I would be interested in your Sherwood, thanks much for the offer!

 

RE: thanks, Sherwood, BTW..., posted on October 31, 2014 at 12:55:13
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 I like your thinking, but alas, I do not think the original will fit in the newer chassis. Some people would chalk up the smaller transformer to Sherwood's accountants trying to save money. However, Sherwood was constantly trying to make their amps physically smaller, as it was one of their selling points. I have a feeling the larger transformer was replaced with the smaller one because it allowed them to shrink the chassis even more.

While the later versions DO run hotter, I've only ever seen one burned out in an amp that had something seriously wrong with the power supply. If you get a re-wound one second edition transformer, it'll be fine unless all your caps get leaky and you keep running the amp anyway.

But no, I do not think it is possible to physically fit the first rev. tranny into the second rev. chassis.... Sorry!

 

RE: thanks, Sherwood, BTW..., posted on October 31, 2014 at 13:13:29
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, Sherwood, I'll pass along the specs to Heyboer and see what they can do...

 

RE: thanks, Sherwood, BTW..., posted on October 31, 2014 at 13:25:40
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 BTW, is the parts set a long or short body S-5000, not that it really matters but if a long body I would probably want to put that one working first. Also, do you have any dimensions for the short body power tranny, since mine has a replacement tranny, I don't know the true dimensions of the original... thanks

 

RE: The Monster Amp, posted on October 31, 2014 at 15:44:11
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hi,

It's a short body. It had cosmetic issues to begin with, and I already yanked the OPTs and built a little stereo amp in a Hammond chassis using the S-5000 circuit for the power amp, and the Triode Electronics ST-70 driver board for the front end. I think I nabbed a power tranny from an S-4400. Quite a cool little amp, even more headroom and authority than the S-5000, quite probably because there were far fewer tubes loading down the power supply.

Anyhow, not to get too far off topic, I wouldn't have parted out a long version S-5000 unless it was horribly ugly. I would have had it re-wound (though at the time S-5000s were cheap and plentiful). The most I ever paid for one was like $300 for a PRISTINE example with original case and no faceplate wear, all original tubes. Back then (late 90's) I could find these for $150 all day long. Should have snagged more of them.

 

RE: The Monster Amp, posted on October 31, 2014 at 17:15:50
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hey, one more thing...

Post more pics!

Let's see that faceplate, the open belly, etc....

If it's the kind of dirt I'm thinking it might be, (pics!), the most aggressive thing I would use on these early Sherwoods is SPIT and a microfiber cloth, and a judicious amount of friction control, patience, and persistence. Sherwood sadly used an inferior paint on these early models. By the time the S-8000 and whatnot came around in the early 60s, the paint was an enamel like gloss finish that was far more resistant to damage. Whenever I've given somebody a Sherwood, I always gave them careful instructions to never let their fingers touch the faceplate at all, especially when turning dials. Fingernails will eat these things up BAD and you have to be super careful cleaning them.

The steel chassis can get rust flecks and or dust pitting, cleaning it with lighter fluid works well, rust is best removed with the old tin foil and water scouring trick.

Let's take a look underneath. Mike Samra and I have seen a lot of these things, so maybe we can help you undo any hackery that's been done and get the power supply rebuilt. I have both SAM's and the original Sherwood schematic, though I would need to scan them somehow... But anyway, you're really gonna like this amp when it's up to snuff.

 

OK, here is a pic of the belly..., posted on November 1, 2014 at 21:16:59
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005



it's actually pretty clean and looks good, but the offending tranny is pretty obvious by its hacked-in wiring...

 

RE: The Monster Amp, posted on November 1, 2014 at 22:06:27
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Wow, that's umm... Interesting....

Good news is that most of the amp is in terrific shape from the looks of it.

Other than just the obvious, the oddball transformer and the e-tape connections, one thing stands out like a sore thumb: Where the hell is the bias rectifier? Stock S-5000 has a selenium rectifier on the other side of the amp, and the wires to it pass through the eye hole you see on the upper right hand corner of the picture. It feeds into the cap near that hole, which provides both the bias voltage and the DC filament supply. At least from this picture, I don't see how the hell that is even being powered. Are there diodes hidden in that big ol' wad of e-tape?

Anyhow, I sent an email to my buddy who has a lot of my Sherwood stuff in storage. He said he'd go check out the transformer this weekend, measure it to see if it's dead, and pull it out.

I guess the thing to do, if you want to see if this transformer in there has any hope of working, is to figure out what the various taps are and if they are even close the the proper arrangement. Apart from having a HV secondary that is good and high, as well as a bias tap that properly powers the DC filaments and still results in the correct bias voltage to the balance pot, well... It's a tough proposition frankly.

At the end of the day, this amp looks really good, though I'd like to see more of it! I don't see any evidence of rust or hackery beyond the obvious power transformer issue. A proper tranny and some power supply caps ought to make this amp sing.

Also, how did you fare on the tube compliment? Did you manage to get any of the original set?

Cheers!


-SF

 

RE: The Monster Amp, posted on November 1, 2014 at 22:34:06
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005



yes, you see the issue, I don't think the replacement tranny HAS a bias voltage winding, the wired kludge I removed I believe was used to provide bias from an outside source, you will see from the top pic that the selenium is totally missing and it was in that hole that the kludge wire was passed thru to the underneath. I should get around to doing a measurement of the voltages on the replacement, but even so, I think that the replacement is not even close to what I would need to get this right. The top is pretty dirty as you see, but it does clean up to a fair shine, not much in the way of corrosion. I did get tubes with it, including a Mullard 5AR4, but the remaining tubes were all Sylvanias with a bad 6BQ5. If you have the cover plate for the front tubes, mine is missing, and the power tranny would be useful even if blown as I could have it rewound at TRS, they did a Mac tranny from a C10 (preamp), as well I need a front knob, I'll post a pic from the front to you to see tomorrow, thanks SF!

 

RE: The Monster Amp, posted on November 5, 2014 at 17:40:52
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 SF, don't know if I posted this back o you before, but if you have the dimensions on the S-5000 shorty power tranny, could you send that to me, I am in contact with Arlyn @ Heyboer and she needs that info to give me an answer on making a new PS tranny... thanks!

 

RE: Your S-5000, posted on November 6, 2014 at 17:01:16
Sherwood Forest
Audiophile

Posts: 240
Joined: October 7, 2014
 Hi,

I only have mine on hand to measure, and it's in my amp. Hopefully laminate dimensions are enough...

4.15" long
3.45" wide
1.35" thick

Also, it does have a copper shield band, so that might effect the price a little.

Cheers,


-SF

 

RE: Your S-5000, posted on November 6, 2014 at 18:42:34
gkargreen
Audiophile

Posts: 1562
Location: DC
Joined: February 5, 2005
 thanks, SF, that will do nicely, I will send that info onto Heyboer and see what the hit will be...

 

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