Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Misc Schematics and Layouts => Topic started by: Helmut on February 19, 2011, 08:42:34 am

Title: Ampower Model 80
Post by: Helmut on February 19, 2011, 08:42:34 am

===> Does anyone have schematics or manual for Ampower Model 80 ?

I recently purchased a 1940's Ampower Model 80 tub amp at a garage sale. The guy said it worked before and now he couldn't get it to work, so it was very cheap, but probably not in best hands...

I think that one of the power tubes and the rectifier were swapped, so I swapped these and they all lit up. The rectifier was scarily bright, but that may be normal. I'm no expert.

So I bought a set of new tubes and tried it, and then the fuse popped after a minute or so. Still no sound though.
I bought a few fuses to have more attempts, but I really need schematics or a at least a manual.

Please if anyone reads this who owns the same amp, please respond even if you don't have any schematics.

Thanks!
Helmut

Title: Re: Ampower Model 80
Post by: stingray_65 on February 19, 2011, 11:44:15 pm

Hi Helmut!

Before you blow another fuse, it is my suggestion you build a lamp limiter.

Google it up and you'll see it's a very inexpensive circuit to build and very handy in your situation.

A schematic is not always necessary, a lot of amps of that era are not very complex.

The rectifier tube will likely have 4 wires coming off the transformer 2 yellow and 2 red ones, colors may vary and also fade with age.

the yellow ones will be at pins 2 and 8 the red at pins 4 and 6.

power tubes will have a wire from pin 4 to the output transformer.

You will likely have a field coil speaker,

A field coil speaker will have 4  wires running to it, 2 from the output transformer and one coming off the B+ from the recto tube and then returning back to the amp. before the days of affordable permanent magnets, the power supply would feed an electric magnet on the speaker and it would in turn act as a choke for the power supply.

NOW,
unless your dead set to restore this amp, you got a pretty good platform  to gut and put a proper guitar amp into.

Post some pics if you can, nice juicy closeups of the guts if you can and a few to show some details of the cab. Maybe we can see whats going on.

First guess is a shorted electrolytic in the PS section. with any luck the PT is still good!

Ray

Title: Re: Ampower Model 80
Post by: Helmut on February 21, 2011, 02:54:14 pm

Thanks for the response. Attached are some photos of the guts of the amp.

I believe the rectifier should be the front most tube.

Does anyone know what the lever switch does ?

Thanks,
Helmut