Carlsbro Top100 refurb project - someone messed it before me

[JohnnyCreepy]

I picked this today. Paid what matched and unused EL34 quartet cost for it.

So what I got:
-4x United Electronics 6ca7 (dating to 3/76?)
-1x Siemens ECC81 (*)
-1x Siemens ECC83 (*)
-2x TAD 12AU7 (wtf? )
-Patridge 4-8-16 ohm OT
-Filament trafo 6.3/2A x 2 (*)
-PT 220V to 400(0.2A)-0-400(0.2A)-5(2A)-6.3(3A) (*)
-Chassis with some reusable components

(*) = identification request if ya please

So the circuit board looks good, but all e- and poly caps look bad. Wiring is messy, repairs are sketchy and there’s oddball innovations with paralled resistors and series diodes. So complete rebuild is needed here. Gonna disassemble it and test trafos before doing anything more.

And yeah, here are the pictures!




Does anyone recognize stamped logo on PT shown on the last picture?

 

[jwin615]

Maschinenfabrik Reinhausen maybe?

 

[Asdrael]

The tubes alone make it worth it really. And the e-caps don't even look bad from the pictures, or at the very least they haven't leaked. The cable management and "add-ons" are interesting though...

No idea about the PT - think it's original?

 

[JohnnyCreepy]

The tubes alone make it worth it really. And the e-caps don't even look bad from the pictures, or at the very least they haven't leaked. The cable management and "add-ons" are interesting though...

No idea about the PT - think it's original?

Ecaps have leaked, unfortunately pictures do too much justice here. PT should be matching Patridge, not two ones! One tube socket has arced and replaced with old burn marks on chassis. Maybe that’s taken original PT?

 

[Asdrael]

I had a quick look and it seems there are some schematics flying around so at least you shouldn’t be going in blind… that’s already something if you want to do a 1:1 restore. And someone was nice enough to write 12ax7 = ECC83 so you have a starting point

 

[JohnnyCreepy]

I had a quick look and it seems there are some schematics flying around so at least you shouldn’t be going in blind… that’s already something if you want to do a 1:1 restore. And someone was nice enough to write 12ax7 = ECC83 so you have a starting point

PT1 5V @ 3A & 6.3V 3A
PT2 6.3A @ 2A & 6.3A @ 2A

EL34 draw 6A and preamp 0.6A.

Would hooking one pair of EL34 to PT1 and other pair and preamp heaters to PT2 pushing luck here or would it be wiser to rectify to DC heaters for whole amp?

 

[Asdrael]

I would not ride heaters at the limit in general really. And at least with those taps, unless there is a CT or the PT2 has opposite phases, I don't see how you can get to 12V DC? And anyway, rectifying more than say 2A is kinda tough without some form of heat dissipation.

Seems you are stuck with 1 pair of EL34 on PT1 and the second pair + 12aX7 on PT2. On switch out the transformer for a leftover if you have one.

 

[JohnnyCreepy]

I would not ride heaters at the limit in general really. And at least with those taps, unless there is a CT or the PT2 has opposite phases, I don't see how you can get to 12V DC? And anyway, rectifying more than say 2A is kinda tough without some form of heat dissipation.

Seems you are stuck with 1 pair of EL34 on PT1 and the second pair + 12aX7 on PT2. On switch out the transformer for a leftover if you have one.

I have a heavy PT with pri230/sec48 what could be useful here, but just found came across this one from my usual suspects: https://en.uraltone.com/electronic-...toroidial-power-transformer-for-tube-amp.html

But what bugs me is PT1 on Carlsbro has primary tap only for 220 and only the test not yet done how it translates for local 230V/50hz wall voltage. But maybe it’ll turn out something workable on sec. 400-0-400 taps, but driving heater taps hard I find bit too unresting.

 

[Hal Harvey]

That Partridge transformer looks beautiful.

Looks like a fun project Johnny!