A few months back, I picked up an old SA-100B off of ebay. There was a LOT of static on it. The static is on both channels and does not change with volume level.
I started trying to trouble shoot it, I was working with someone on audiokarma, but he's had to take some time away and I could use a bit more help. I tried AK first because it's not headphone related (though at ~1WPC, it would be a good electrostatic amp).
Anyway, it's a very low-power (maybe 1WPC) positive ground amplifier, it is also always on.
What I've done so far:
I've replaced the PS cap to no avail.
I noticed that the secondaries of the transformer were not equal when the transformer was connected to the board, I disconnected the transformer and now everything appears to be okay. The two red wires are V+
The black wire is V-
The white wire is the V- off the lamp. The voltages are:
Red(both 1 and 2)-Black: 19VAC
Point is, the transformer is fine when it's off the board.
I tested the diodes, too. In reverse, both show that they are open, forward, one is 0.511, the other 0.509, which should be about right. So, if it's not the ps cap, it's not the diodes, and it's not the transformer, what could it be? I'm considering just replacing the diodes to see what happens, is that a good next step?
The original AK thread is here: http://www.audiokarma.org/forums/showthread.php?t=481150