Don't have any proper photos of this one as I only have the chassis to work on. Decided to leave the cabinet elsewhere. It's a big amp and I have little room!
I've worked on many of these. I quite like the sound of them. Big and trashy!
They are a bit tedious to work on. One needs the proper approach to get them right. In this case the amp didn't work at all. That part was easy (6EU7 tube in place of what should be a 12AX7!). The rest isn't difficult at all, you just need to be patient and re-cap the thing.
When I say re-cap I usually mean change those dried up electrolytic capacitors. That part is obvious and on one of these amps quite easy. But for these amps you'll need to change EVERY CAPACITOR along with every load resistor. They are noisy. Every Sanagamo cap was leaking or dead. The tremolo was completely dead. That entailed replacing an open 330k resistor along with all the tremolo circuit caps. Also need to replace the load resistors. The 6AU6 tube was good, they usually are.
Tremolo circuit:
The 330k 'feed' resistor I'll be replacing with a 25k trim pot. Once I got the tremolo to work it was simply weak. I reduced that resistor to 50k and it's way better, but it can be great so let's go for that.
More shots inside the chassis:
Phase inverter/driver circuit:
One of the peculiarities of these amps is the filament arrangement for the 12AX7 tubes. Those are D.C. and powered from the cathode resistor on the 6L6 power tubes. They are wired in series with about 28 volts going across both tubes. The nice part about this was I have 2 modern Tung Sol 12AX7 tubes that hummed under any normal arrangement. I couldn't sell them. But in this amp with the DC filaments they run nice and quiet.
Bloody modern tubes! Got a set of modern Tung Sol 5881 tubes I dropped in this amp. One is bad....
I couldn't find a schematic so here is one that has some similarities:
Tremolo circuit is 90% identical along with the preamp....
Amp runs pretty quiet now. These will never be as quiet as a good Fender but don't let that stop you from considering one. If you get one don't bother trying to trouble shoot the issues, just bank on spending a few hours replacing every cap and every load resistor in the house. No sense in playing whack a mole with your valuable time! And please don't buy into that "but the original sound" bullshit! You can buy carbon composition resistors all over the place now thankfully, and I like those Mojo Dijon capacitors for my signal path. Get in there, get your hands dirty and get it right! Worth the effort!
I can say the same with every other Silvertone amp I've worked on. They were pretty crappy amps to begin with but that is their charm. They used the cheapest parts available so 55 years later......
JB
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