Anyone have experience rebuilding a Fisher SA-1000? I'm chasing a "soft but audible buzz". I suspect a power supply problem... Any suggestions?
Any luck on fixing the buzzing noise? I believe it would be 120Hz power supply hum that came from the ground loop somewhere in the amp.
Is surely cause the supply voltage doubler it will need a major recap maybe a choke and more decoupling (originally it has only a total 100uF at the main HT supply) from I remember, this amp isnt the better from Fisher regarding the cheaper ones, it has some hum and stability issues even coming from factory, an uses rare and costly tubes, you know these amplifiers have a legend behind them but I didnt saw anything worth the current collector price it currently has
I have one that seems to generate the same buzz at very low volume. I was trying to find the source of the buzz but not easy to trace the cause. I will update on this trouble shooting if I succeed.
The first thing to do in terms of tracking down noise is to figure out where it's getting into your signal path by the process of elimination. With tubes, it's easier than with SS because stages tend to be capacitor-coupled.
Looking at a picture of an SA-1000, it looks like the selector switch wiring is kind of out in the open. That could pick up noise.
Looking at a picture of an SA-1000, it looks like the selector switch wiring is kind of out in the open. That could pick up noise.
Williamson plus cathode feedback with a Sallen-Key filter in front. Fisher was not afraid to study from the best.