Hot Sherwood S5000

UF4007's.....are those quieter versions? I've never used them. I've got some 22 gauge teflon/silver wire. What gauge did you use?

UF4007s are quieter. I've never used any 1N parts for anything so I can't say if it's particularly noticeable to the ear, as opposed to test equipment. They're both ridiculously cheap so I just use the UFs. When I've used them in power supplies I've snubbed them with high voltage caps - 0.01uf 3000v. I wouldn't bother with snubbers in a bias supply like this. There are other types of diodes that are even quieter. I don't use diodes much so . . .

The wire I used was 20 gauge. The wire I replaced might have been thinner so 22 might work fine. It was more work but the original wire was pretty rough so I went with peace of mind - I wouldn't want faulty insulation to put 400+ volts onto the chassis. Ouch.
 
Jumpers are for altering the damping factor, I believe with the jumper is a lower damping factor (2?) than without. Try it both ways, there should be no danger in either. Mine has it in.

From some old Sherwood sales literature: "All Sherwood amplifiers now provide selectable damping factors of 10/1 (normal) or 2/1 (for use with today's popular compact speaker systems)." DF is a measure of the amp's ability to control the bass. No harm trying it in either position. One may sound better than the other depending on which speakers you're using. If you don't use the jumpers they can just be rotated out of the way, no need to actually remove them.
 
Powered it up to about 84vac. Measured pin 9 of output tubes and got 288v. Went to measure the bias supply and I think it read 15v but the 150/50 cap popped right about then.
Shut down variac.
Must have wired something wrong. And the 47ohm 5w resistor was hot.
Had a hum coming from one channel but no music from source.
 
make sure the cap isn't backwards. Bias supply should be positive lead to chassis ground.

Also if you replaced the selenium, make sure the silicon diodes are facing the right way. For a negative DC supply, the stripes want to face the transformer leads.
 
Diodes and cap were as indicated. This was that "positive can". I set a terminal strip with a chassis ground in the center and built it up. Here is my crude sketch of what I did. Maybe something will stand out wrong (I left out all the incidental wires).
This may make your nite:
puff.jpg
cap sch.jpg
BTW, that 33ohm resistor is a 47ohm on mine.
 
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Diodes and cap were as indicated. This was that "positive can". I set a terminal strip with a chassis ground in the center and built it up. Here is my crude sketch of what I did. Maybe something will stand out wrong (I left out all the incidental wires).
This may make your nite:
View attachment 907357
View attachment 907329
BTW, that 33ohm resistor is a 47ohm on mine.

Here is the schematic from Sams for the bias supply on the S5000. Comparing it to the version you posted there are several differences starting with the polarity of the diodes. Also the multi-section can looks like it is common neg not common positive.
 

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Here is the schematic from Sams for the bias supply on the S5000. Comparing it to the version you posted there are several differences starting with the polarity of the diodes. Also the multi-section can looks like it is common neg not common positive.

And I stand corrected about all the filaments being AC...my bad. Like I said I'm a hobbyist not a tech and I know it.
 
Attached is the factory schematic shown together with the Sams schematic for the S5000. Appears to me that Sams drew the diode schematic incorrectly, but labeled the anode and cathode correctly with the + and -.
 

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?
Are you indicating that my problem may well be that I installed the diode with the positive toward bias supply as indicated on my schematic? OK...but my design had a SR not shown on either schematic. I need to look at some new schematics I received tonite to see if they match my unit.
Aside from that, both schematics would match my "multi-cap" build. And my diodes never went to ground (except through the .015uf caps I added.
I would think that the direction of a diode is pretty much universal due to its function.
 
hm, either that Sams schematic has the caps and diodes backwards, or its not a negative DC supply. As-drawn it should make +20 vdc. If it connects to the grids of the output tubes, it would need to be negative.

Diode orientation is just a matter of what polarity you want. Doesn't much matter what the rectifier technology is, they all do the same basic function.
 
hm, either that Sams schematic has the caps and diodes backwards, or its not a negative DC supply. As-drawn it should make +20 vdc. If it connects to the grids of the output tubes, it would need to be negative.

Diode orientation is just a matter of what polarity you want. Doesn't much matter what the rectifier technology is, they all do the same basic function.

Yes, there is a major error in the Sams. I had forgotten about that. The diodes and caps are backwards as you say. The banded end (cathodes) of the diodes connect to the blue wires from the transformer and the other end (anodes) are connected together. The added resistor (again, I used a 10 ohm) connects to the junction of the anodes. The caps are positive ground. It is a negative DC supply and it also provides DC for the heaters of the phono section tubes.
 
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Which Sams is correct? My serial number is 511300.
Or which schematic do I use and change direction of the diodes? Since my resistors are of different values as those shown, there may be a correct one floating around for my particular unit.

The selenium rectifier I took out was had red paint at the center connection to supply. Would that indicate that the positive side of the diodes attach to supply?
 

Here's a pic of how I did mine.

Keep in mind that there are different versions of the S-5000 that use 7189 / 6BQ5 outputs. The one I have pictured is the version that has the 12AX7s mounted at an angle with individual tube shields on each. The other version - one you have - has them mounted vertically and enclosed under a cover. I'm not sure if there is a separate Sams for each version. Even if there is, Sherwood was famous for making running changes to their production line without making any change to model numbers so it is common to find differences between what is shown on a schematic and what is actually installed on any particular amp.
 
I have a couple of the vertical tube versions too. I haven't done a proper restoration on either of them but I may have replaced the selenium diodes at some point. The parts are mounted differently but I think the circuit is essentially the same. Just orient the diodes and the caps correctly and use whatever value resistor was in there. You can tweak that later if necessary.

In the pic above I just left the stock can in place for looks. The terminal strip on the side was mounted where the selenium was removed. You can kinda see how the diodes are oriented (banded ends to the blue wires from the transformer) and the 10 ohm resistor added. The positive of the three replacement caps all go to a lug on another terminal strip that I mounted using a transformer bolt. They all connect to the center tap of the secondary that powers the diodes (the blue/yellow striped wire).
 
Thanks. I guess I might not have an understanding of this "positive can". Here is a photo of the bottom of the old can.
IMG_5037.JPG
I wired my caps as if these tabs were positive. So I connected the other end of the caps to ground. Were these tabs not positive?
 
Thanks. I guess I might not have an understanding of this "positive can". Here is a photo of the bottom of the old can.
View attachment 907582
I wired my caps as if these tabs were positive. So I connected the other end of the caps to ground. Were these tabs not positive?

I'll try to pull out one of mine that has the vertical tubes like yours and take a close look at that can cap. Hopefully this evening.
 
?...but my design had a SR not shown on either schematic. I need to look at some new schematics I received tonite to see if they match my unit. Aside from that, both schematics would match my "multi-cap" build. And my diodes never went to ground (except through the .015uf caps I added.

First, and someone correct me if I'm wrong, I don't think the symbol for a selenium diode is any different from a silicon or other type. The problem may be in how you installed the .015uf caps. When caps are used as snubbers to reduce noise they are installed in parallel with each of the diodes. They are not connected to ground.

I guess I might not have an understanding of this "positive can". Here is a photo of the bottom of the old can. I wired my caps as if these tabs were positive. So I connected the other end of the caps to ground. Were these tabs not positive?

I pulled out one of my S-5000s that has the vertical 12AX7s like yours. First, the can itself lists the voltages of the three sections as Neg 50v and below that it says Can Pos. I opened mine up and, as I remembered, I had replaced the selenium rectifier and added a resistor. Here's a pic:
04040002.jpg
On first glance it looks like this is a normal can cap in that it's mounting tabs are soldered to the chassis. But you will notice that after the 10 ohm resistor is connected to the first section (at ~8am in the pic - I think its the 150uf?) the 2.2k 1w resistor is connected to a fourth tab (at ~1pm in the pic) which also has the CT (striped wire) and a couple of black wires on it which are going to ground. If you replaced one or more of the sections of the can with a separate cap you should have connected the + of the new cap to that fourth tab.
 
The flat line = + and curved line = - interpretation of the capacitor schematic is an old assumption and clearly a wrong assumption in the factory and the Sam's schematics. The Sam's schematic is bad, throw it out. Use the factory schematic. Since it is a negative supply the positive lead of the electrolytic goes to chassis ground and the negative lead goes to the negative bias supply.
 
What he said, stripey side of the diode to the transformer leads, + side of the capacitor to chassis. Should be can common positive for the bias supply cap, and each terminal would get a negative lead. Factory schematic is electrically accurate, though it would have been nice if they had clearly marked the cap polarity.
 
Now I'm really confused. Think I will just switch my caps around and cross my fingers. I had them neg to ground. Will also take the .015 caps out. Read somewhere that adding a .01uf from the diode to ground would filter out any noise. I rebuilt it using some 1N5408s which I think would solve that problem, if there was one.

As there was a tab on that can that goes to the neutral bar and a tube, I isolated it from chassis ground in my "rebuild of the cap" (previous sketch).

FLA
Did you add the 10ohm?
 
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