Over Easter weekend I was given a Counterpoint SA-20 hybrid audio amp and matching SA-1000 preamp. The list price for the set was $3890 in 1989 dollars. Adjusted for inflation, that’s $7412 in 2013. Not bad for the low price of “Get it out of my basement!”
When I got it home, I plugged it in and immediately let the Magic Smoke out. It looks like the driver for one side was damaged before the amplifier was put into storage. According to the former owner of the part, the same thing happened the first time he plugged it in. Internet searches show this to be a pretty typical problem with this amplifier. The power MOSFETs are apparently a bit delicate.
Repairing this should be a fun project. It seems that the MOSFETs used in this amp are no longer produced. (Get model number). The assortment of charred passive parts should still be sourceable provided that they’re identifiable.
The repair manual is available for purchase at AltaVista Audio. The site is run by the founder of Counterpoint. He used to do repair services, but is now retired. IMHO, $80 for the service manual is a bit steep for a PDF file, but that’s the way it goes. None of the Hifi shops in the area that I’ve contacted have had the manual either. Scarcity FTW.
There are two ways to proceed:
- Reverse engineer the schematic from the amplifier.
- Chuck the current guts of the amplifier and build something new using the sweet looking chassis.
I’m leaning towards the latter option at the moment. There’s quite a bit of damage.
Here are a few images from my cruddy camera phone: