Tempo by Univox 5 watt, 3 input

[DFuller]

Like so: https://reverb.com/item/30601794-196...mplifier-japan

I can't find anything on these, and so I don't spend a couple hours tracing and drawing this thing out... Anybody got this by chance?

[Enzo]

I don't, but it looks like a pretty simple amp. Two hours? I hope that includes a sandwich...I have stacks of hand drawn schematics.

[DFuller]

I don't, but it looks like a pretty simple amp. Two hours? I hope that includes a sandwich...I have stacks of hand drawn schematics.

Maybe a slight exaggeration, but eh. The layout is weird and not at all what I'm used to - and PCB amps don't bother me, most of the time.

[dmeek]

If you can, post photos of the PCB, both sides

[The Dude]

It looks like a pair of preamp tubes and probably a SE EL84 output configuration from the pics. You could help us by at least stating the tube compliment. It probably wouldn't be difficult to find a similar amp schematic. Otherwise, I agree with Enzo, it shouldn't take too long to draw it up.

[DFuller]

If you can, post photos of the PCB, both sides

Sure thing.
Apologies, they're rather large.

[DFuller]

It looks like a pair of preamp tubes and probably a SE EL84 output configuration from the pics. You could help us by at least stating the tube compliment. It probably wouldn't be difficult to find a similar amp schematic. Otherwise, I agree with Enzo, it shouldn't take too long to draw it up.

1 12AX7, 1 6AV6, and a 1 6AQ5. Controls are (from left to right, with the pot casings facing you): Tremolo depth, speed, bass, treble, and volume. From the tracing I've done so far it looks like half the 12AX7 is for the preamp, half is (I believe) for the tremolo oscillator, and the 6AV6 is the driver.

[g1]

I think Enzo may try to sell you a napkin.

[Enzo]

Oh well foo... I was guessing 6C4, but I got the other two.

Any chance a bright light shines through the board? That would reveal the traces while looking at the parts. Even so it won't be hard, but...

[The Dude]

Maybe similar to this sans the tube rectifier?

https://www.prowessamplifiers.com/sc...Univox_U45.jpg

[Enzo]

I would guess not very different.

[DFuller]

Oh well foo... I was guessing 6C4, but I got the other two.

Any chance a bright light shines through the board? That would reveal the traces while looking at the parts. Even so it won't be hard, but...

Tried that, unfortunately no. This amp is strange though. So far as I can tell, there's only one rectifier diode in the whole amp (which is hidden by the can cap - it's what that black wire from the PT connects to), unless I'm really looking right at diodes and not seeing them.

Maybe similar to this sans the tube rectifier?

https://www.prowessamplifiers.com/sc...Univox_U45.jpg

Yes, similar for sure. Some different component values here and there, plus the tonestack instead of a tone control, but overall not super different, so far as I can tell...

[The Dude]

It's probably cathode biased, so no bias supply. It could very well be built with a single rectifier, although I'd not expect that on a SE amp.

[DFuller]

Drew out most of the circuit (minus the tone and tremolo controls)... I think someone has tweaked the circuit, because there's a pad missing a wire that has solder on it. But, that's around the tonestack, so not included here.

[g1]

So far as I can tell, there's only one rectifier diode in the whole amp (which is hidden by the can cap - it's what that black wire from the PT connects to), unless I'm really looking right at diodes and not seeing them.

If you mean under the cap there, then maybe there are 2 of them? Very strange.