First console pull, does this look worthwhile?

[downhiller20]

hard to guess on an unrestored piece. Clean the controls and check the cables between the preamp and power amp. Also might be worth switching tubes channel to channel to see if the problem moves. Honestly with half century old caps and resistors in there though, I can pretty well guarantee its got some parts out of tolerance so that may very well be the issue. If you think it sounds good now, wait till you hear it when its actually working all the way right.

I've got some little easy to drive paradigm micro monitors hooked up to it and really sounds good for a $10 amp. Very full with lots of energy like a class A SS amp, but with some lushness on top. Is there any good links to console unit restorations on here? It is kinda a weird thing to search for as I'd like to find one similar to this amp to follow.

 

[gogofast]

find the schematic first. with schematic, a simple single ended amp such as yours with point to point wiring should be a piece of cake to troubleshoot and restore. meanwhile, make sure that you're fully aware of the dangers these amps present especially when hooked up like that. it's easy to overlook precautions.

anyways, i can see a beautiful restored standalone amp. good luck with the restoration.

 

[downhiller20]

This looks to be the same amp as mine, and he already set me up for success, now for more research!

http://www.angelfire.com/vt/audio/se6bq5.html

 

[Dandy]

Nice link. You could send a (very soft) signal direct from your ipod to the each of the grids of the 12AX7. Use a 0.1uF cap between the signal and the grid (the input marked on the schematic), with the signal grounds connected to the amp ground somewhere. That will help to check if the power part is working okay.

If it's not a simple mechanical break somewhere, suspect the caps first. I had to replace all mine before it worked properly. Also clean switches.

And watch safety while it's apart, even simply stuff like the AC switch. It's easy to forget this when you're wondering where a fault is.

 

[scottfan]

No idea what these are

Amprex el84s. Mullards have a round hole in the plate and often look smoky.

 

[downhiller20]

Had a knowledgable tube friend come into town and he drew me up a schematic of the amp itself since I had it on me. I still need to figure out the preamp section. How should I go about tracing it? He suggested I use the original design since there is a feedback loop used.

Overview of his schematic
http://imgur.com/mdZ2BT8
Power supply
http://imgur.com/MeJtNAQ
El84
http://imgur.com/rJAEbOd

Here is what I believe to be part of the preamp section
Bottom of the 12AU7, the two wires that go into the black heatshrink and are connected to the tube via the big black resistors feed the EL84's
http://imgur.com/CXJWh4P
Bottom of a 12AX7, not sure what it going on here
http://imgur.com/1de1fyI

 

[wa2ise]

Be sure to wear footwear when working on tube electronics.

---------^^^^
Seriously, there's a few rules to follow to avoid shocks, and to minimize the consequences of a shock. Idea is to keep the shock current away from your heart. Your nervous system's control signals are about 100mV, so 250VDC can cause interference... Shoes, long pants, long sleeves, and one hand in your pocket when probing around tube electronics when it's powered up (like taking voltage readings).

 

[Tom Bavis]

3H32 and 12H26 are covered in Sams folder 633-14. Not in my Sams collection, but the 3B32 amp chassis is similar (if not identical), shown here: http://techpreservation.dyndns.org/schematics/60/60_Zenith_3B32_177.djvu (you'll need the DjVu plug in to view or print it).