Schematic for oddball Sano amp

[Yoda]

Hello all,

I just received an eccentric Sano tube amp for repair, appears to be a stereo accordion amp with reverb and tremolo, with a single 15” and a pair of 8” speakers.

Needs filter caps and updated power cord. The rectifier is a 5U4 and the amp has two 60/20/20/20uF cap cans but I cannot find a modern replacement in these exact values, I’m wondering what I can substitute without exceeding the rectifier tube’s max input capacitance. The 5U4 data sheet lists 40uF here so I’m already skeptical about the original can values being higher. The closest modern cans I can find are 60/40/40/40uF, or 40/20/20/20uF by CE.

I’m also having difficulty locating a schematic (Schematic Heaven had some Sano amps but not this one. This model appears to be called the 500R.

[timrobertson100]

This thread claims to have the preamp schematic (last photo).
Cheers

Edited to add: From this reverb posting there is this which seems better a better quality photo:

[Stevem]

If you have the room to glue down separate preamp filters on fish paper go that route.

Then you can run a somewhat star ground set up from the high current output stage filter and have a lower 120 hz noise floor.

[Yoda]

That looks very close, thank you so much! I can’t find anything better than that on the web.

There is a page that supposedly has it but you have to send $20 via PayPal, not sure how I feel about that.

I really appreciate the help guys you guys are a gold mine.

[Yoda]

Sometimes the reverb works, sometimes it doesn’t.

[Yoda]

The reverb tank tests good but there’s no reverb, not sure what happened because it was working and now all of a sudden it’s not.

[Yoda]

Where would you guys start in diagnosing the reverb? The schematic posted above for the 500R appears is correct. I can post pics of the guts but it’s point-to-point so it looks like a rats nest.

Thank you.

[Kagliostro]

Sano.jpg

Franco

p.s.:I aplogize, when I posted I linked a wrong version of the file, now it is correct

[maxkracht]

Where would you guys start in diagnosing the reverb? The schematic posted above for the 500R appears is correct. I can post pics of the guts but it’s point-to-point so it looks like a rats nest.

Work on enough rat's nests and they start to make sense. First step is to figure out if the problem is before or after the tank. Smack the tank and get a crash, the output is fine, look at the driver side. No crash, look at the return side. Can swap the input and output on the tank and check for a crash again. If you get a crash on both sides the tank is fine but the driver side has problems. You can jumper around the tank to see if the rest of the circuitry passes signal, should get a volume boost. Do voltages look normal? If it's intermittent, chopstick around, wiggle tubes, twist and wiggle rca connectors, check cables, etc.. Do all the normal troubleshooting stuff.

[trobbins]

The schematic is not imho showing the jfet correctly for the tremelo function. Afaik, the jfet input would be driven by the low frequency oscillator, and would be shunting V1A or B's cathode to ground, or not. Also the Depth setting introduces feedback to the oscillator, which is interesting.

[chordball]

I would trace the whole reverb circuit and verify what tube it is wired for vs what is in there. I have a 250R and while the schematic shows 6CS7 as yours does, it was wired for and had a 6CG7 installed. I just found a 300R on Reverb that has a picture of the tubes (last photo) and, you guessed it, it's a 6CG7.

https://reverb.com/item/77702988-1979-s ... e-tube-set

The cap coupled reverb is fantastic though, and if yours doesn't already have a proper reverb pan I highly suggest getting one. Mine had the little OC Electronics pan in it which did sound nice, but the 3 spring Gibbs pan I replaced it with made it even sweeter.

[Kagliostro]

.... The schematic is not imho showing the jfet correctly ....

I agree with you, the simbol that was used is the simbol of an SCR Diode

As I'm not confident with Jfet and other Solid State components, if someone can put on the actual schematic where are placed the Source - Drain - Gate connections I'll try to revise the schematic with the correct Jfet simbol

2N5461.jpg

Franco

[trobbins]

Franco, I'm not too sure - will have a look.

[sluckey]

if someone can put on the actual schematic where are placed the Source - Drain - Gate connections I'll try to revise the schematic with the correct Jfet simbol

[Kagliostro]

Thanks again Steve

Franco