Nice Iron, what to build??

[Toxophilite]

Here's an old Sherwood S-100 Mono 40 watt amp I converted a long time ago when I was even more of a butcher. It worked but I was just basically rerouting the signal path and adding a fender tone stack.
it was very pretty but my wiring was pretty lame and the chassis is largley very shallow

2  7591s, originally a GZ34 rectifier
i think the iron is great and I think the PT puts out a lot of oomph


Maybe a vibroverb, super,?


Interesting how the transformers seem to be orientated the same way

[jazbo8]

There is no S-100 model, it's a S-1000, and the original tube compliment were 6L6's and 5Y3-GT. So someone must have swapped the tubes. It's originally rated for 20W. Did you disconnect the ultralinear connection and run the output tubes in pentode to get more power?

[Toxophilite]

My mistake
I meant S-1000
And it actually has the original tube chart that shows the 2 7591
They also made a 4 6BQ5 36-40 watt version that ran at 452 VDC so I think 7189s were recommended
I had 2 nice ones of those at one time as a hifi stereo setup
I've seen the 6L6GB shematic, and the 4 6BQ6 one but I've never found one for this amp
I didn't do anything to the way the power amp wiring except try to replace filter caps and the odd resistor that was burnt when the original can cap started to go. I didn't know enough to mess with power amps then.
I'll try to get you a photo with the tiny manky tube chart. My camera batteries are dead so I'll do it tomorrow
But the 7591s are original, as is the power amp, though someone did solder in a pair of diodes on the inside of the rectifier socket which is funny because I think it came with a GZ34 which is also on the chart
Anywho it's a rusted old thing with the original faceplate all trashed(I took it off) but certainly the Transformers are still good. and nice quality too.

[DummyLoad]

probably a transitional model to use up the 1000 chassis before transitioning to the model 5000? there's documentation of it, just no schematic to be found in cyberspace.


harvest the iron, scrap the chassis: use the 17x6x2.5 chassis that doug sells and build a vibroverb minus the vibro. use GZ34 as in original. reverse engineer PS and output stage. take lots of pics. 


--pete

[jazbo8]

+1, there is no documented S-1000 with 7591 & GZ34, you may have a rare bird, too bad it's all beat up...

[sluckey]

Since you already have several Fender builds you may want to look at some Ampegs. Several of the old blue diamond amps used 7591s. Look at the schematics for the G12 and G15 series.

I have an AO-63 that I put an Ampeg preamp in. Sounds pretty good. Reminds me of my old Gemini II but without the reverb/tremolo. I may finish that project this winter.

 

[jazbo8]

How about a Dumble ODS mod based on the Super Twin? Since the Sherwood has the UL OPT, might as well use it.


https://www.youtube.com/watch?v=NvkB2wETTBc

[Willabe]

Interesting how the transformers seem to be orientated the same way

They are but but they are far away from each other. And both PT/OT are shielded with 'bell' ends pointing up, where the most noise would radiate from. PT also has copper band.

[Toxophilite]

You know I don't think this OT is ultralinear. It seems to have the regular amount of taps
3 on the primary side (brown blue red)    and  4 on the secondary side.(Com 4 8 16)
I think they made many variants
Even the two other mono amps I had which both had 4 6BQ5/EL84s had quite different preamp tubes. I think one of them had a 12BH7..or a 6EU7..I can't remember exactly
It was funny because I was given one and then I was searching hi and low for a matching second one and for the life of me I couldn't find one exactly the same!!

[jazbo8]

The mystery deepens... So there is no extra wires hanging out of the OPT? If so, then you got an odd one on your hands, wonder what other changes there are to the schematic... Are the 7591 cathode biased? What are the other tubes in the unit?

[Toxophilite]

Here's a picture of the tube chart, such as it is
preamp is 3 12AX7


the PT has only the three taps on the primary


the cathodes are all tied together and connected to the filter caps, the OT B+ line and groudn through some high watt resistors...I shrink wrapped some due to shorting problems in the super shallow chassis so it's kind of hard to tell.

[Toxophilite]

If I'd had the brains i would've swapped these transformers into my current build and saved $75 (Can about $5 US)on the Hammond Vibrolux OT

[jazbo8]

Here's a picture of the tube chart, such as it is
preamp is 3 12AX7

It is indeed a rare bird! I would clean up the wiring, and re-configure the gain stages to suit your tonal preference.

[Toxophilite]

Originally I had 2 fender tone stacks on the two available preamp 12AX7
It sounded lovely through JBL D123s but when I checked it a while back the preamp voltages were only maybe 90-100 volts.(I didn't check those sorts of things when I rebuilt the preamp, I was ONLY rerouting the signal path and I had the barest notion of how to do that!)


 You could turn it up pretty well all the way and it would JUST be loud enough to play with my jazz band and it was clean clean clean!
I'm wary of the rusty old chassis because the power supply section is so shallow (maybe an inch)
there's lot's of room in the preamp section
but it's also an awkward shape to mount with weird angled tube orientation
It might be good to start with a schematic, even if only of the power supply , PI and Power amp
So if I do move the iron I can use the tubes and build the power amp into another more usable chassis
And then redesign my preamp, maybe even add a preamp tube