I recently purchased a Sherwood S-5000 int amp and am looking for a schematic or service manual as it needs some work. I've found what appears to be the one schematic available on the internet but it is for s/n 959xxx and up and really for the most part is unreadable and the sides are chopped off. My Sherwood is s/n 957xxx. Any help would be appreciated in trying to resurrect this classic pc of Sherwood gear.

Seems like Sherwood made a lot of different version of this amp with different tube complements- 7189, 7591, 7868, etc.

You might have a bit more success if you post the tube complement yours has....

They made different versions of everything back then it seems!! I have two S-2000 tuners and two S-3000-III tuners and neither is the same and I still haven't been able to find the correct schematics for those either! Anyway, the original S-5000 (not mk2 etc.) only came with 4pcs 6BQ5/EL84 output tubes, and the later version(s) (mk2 etc) did not use 6BQ5, but did use 7868 and others. The remaining tubes in my S-5000 are:

5pcs 12ax7
2pcs 7199 (which I'm going to rewire for some 7687's I have)
1pc 5ar4

Of course from the back the original S-5000 are easy to distinguish due to the narrow output tubes, and from the front there is a bank of 4 push buttons down the LH side of the faceplate.

So what is the question? Sounds like you need 7189's. Vanilla 6BQ5's are really iffy in these applications.

I am looking for a schematic and/or service manual.

My second post was confirming to another post that I do indeed have a S-5000 for the reasons mentioned (and it says S-5000 on the s/n tag), not a S-5000-II.

Old 6Bq5'a qwill not do for these sets. Even the 7189's were somewhat stressed if pushed. That being said a dozen or so of 'em fire up really nicely in my ancient Hammond. Yeah, Holland types.

LOL.

I haven't 'fired' up the tuner yet as it needs to be repaired. I'll be using it with very efficient speakers so hopefully won't be burning through too many tubes as this will be in my 3rd system. I have a quad of vintage US 6BQ5's for initial start up, and I'm working on a quad of 1960 vintage Amperex 6BQ5's for after the fire works!

I have one of these amps and I do like the way it sounds.
Runs hotter than heck and you DEFINITELY need 7189's
in there.The plate and screen voltages are around 400 volts
way too much for 6BQ5's and 7189's are just barely
passable in this design.You also need good 7199 driver
tubes marginal ones will cause hum.
Regards.
Swanson

Thanks for the heads-up Swanson!

I was going to rewire the tube sockets so I could use some 7687's I have on the shelf in lieu of the 7199's which I would have to buy.

It wouldn't be a bad idea to run this (and a lot of other vintage tube gear) on reduced line voltage to make life easier on the unit in general, and the output tubes in particular. This is especially true when the design of the gear pushes the tubes at or above redline (as many "golden age" receiver and amp designs do). A Variac or a bucking transformer is a quick and relatively painless way out.

I use Variacs for my vintage gear, and tune for 105-110 volts. A Variac is more expensive than a bucking transformer, but on the other hand, a single Variac can usually supply several pieces of gear simultaneously without exceeding its ratings. Any loss in performance isn't a loss I'll miss, especially when I think about prolonging the life of the output tubes. When they blow down, they have a bad habit of taking other very expensive stuff (such as output transformers or even power transformers) with them.

No use asking for trouble by leaving such gear on the typically higher line voltages most of us have nowadays.

Good luck with your project.

Larry

Could one reduce the plate voltage to the output tubes only?

I have a GenRad variac but don't think it will look very attractive on my desk. I have a very large 1950's vintage oak secretary desk (you know the one - it has a spring loaded shelf in the LH cupboard for a type writer) that I'm going to be using as a table to set up this vintage system which will include a Sherwood S-3000 III tuner with on-board MPX. I listen to FM radio 99% of the time. I have a choice of speakers sitting on the shelf - Monitor Audio Silver 3i, Monitor Audio Silver 4i, Klipsch KG1, or Mirage M-290is. So lots of power isn't a requirement.

Tom, it's readily possible to make internal modifications to "gear back" the output tubes in any receiver or amp, but it's also unwise to make blanket recommendations about doing it. The "mods" of choice will depend on the circuit, and they often don't involve gearing back the plate voltage itself. Instead, the "throttle" is applied elsewhere in the circuit (grid, bias and cathode circuits, for example).

I understand about Variacs that don't look too good; mine don't look too good, either. I settled for tucking them somewhat out of general view (but not out of reach), and running extension power strips within reach of my gear.

If a smaller Variac could serve you, the old and original General Radio Variacs often pop up at hamfests and on Ebay, usually in good condition. They're no bigger than the average VTVM (the RCA Senior VoltOhmyist is almost identical in size). Most of these GR Variacs are rated somewhere between one and five amps; some are two-wire and some are three-wire.

If you get intrigued about gearback circuits for your output stages, let us know and we'll see what we can do.

Best regards ,

Larry

Thanks Larry. First I need a schematic, then I need time, then I can work on it (when the CFO isn't looking!) to get it going as right now it's non-functional. Then I'll consider the output tube/voltage options. I'm just going with 6BQ5's until I get the amp functioning properly.

Be easy on the 6BQ5's, Tom. As others have said, they're overmatched by the voltages you have here.

Good luck , Larry

Thx, I'll tread carefully!

I don't think there is anything you can do to be easy on output tubes. They're going to be cooking even at idle, with no signal at all.

My thought is that the best way to gear back the output stage is to reduce the screen voltage by adding a resistor right at the screen grid socket lug, or by increasing the value of the screen resistor if there already is one. Pentodes and Beam-power tubes are not very sensitive to changes in plate voltage.

If you use a Variac or a bucking transformer, its effect on the output stage plate current is only via screen voltage.

-David

I have a schematic (from Sams folder 475-9) but can't guarantee that it will match. I also have the Sams folders for the 2000 and 3000, and the Sherwood manual for the 2000 is on my web page: http://www.audiophool.cjb.net/hifistuff.html

I have had good luck with the Russian 7189 equivalents 6P14EB - also sold as EL84M. If you wire the socket for 7687, 6U8 or 6GH8 will work too, so there's an endless supply, unlike 7199s - even the Russian ones are out of production.

email tbavis(at)rochester(dot)rr(dot)com

Hi, there is one one EBay .Would you advise me to buy it ?is it a real good integrated amp?, and at which price? (auction that is running :276 $ at the moment ,in perfect working condition ,according to the seller point of view!look nice actually! )
Thanks
Pascal

I wanted to chime in briefly about the high-voltage wiring on Sherwood tube gear.

On several Sherwood's we've serviced the last several years, we've found that the insulation on the high-voltage wiring was deteriorating. The jacket on the wiring was getting brittle and cracking. In a few places an arc-over, or even a hard short, was imminent. We opted to install new 600v wiring from Alpha (Mouser) or Antique Electronics. All in all, two or three feet of wiring needed to be replaced.

We haven't noticed such a serious insulation breakdown on Fisher, Scott, McIntosh, Dynaco, or Sansui.

Fred
owner
Classic Audio Repair

I used a Sherwood S-5500II for many years. I had rescued this amplifier after it had suffered an "ignition event." It used 7868s and really cooked them -- you can't imagine the heat that would pour off this amplifier. The 7868s were prone to screen-to-cathode shorts which if not caught immediately would result in another ignition event.

I really don't recommend Sherwood amplifiers from this vintage, or anything using 7868s or 7591s. If you have one, I would gear it back by reducing the screen voltage by about 10%. I would not use a Variac or a bucking transformer unless you have serious line voltage problems (over 125VAC).

-David