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I got in a Yamaha StagePas 300 with the complaint that it sounds crackly and noisy. Pots needed some working in, not sure I like these hermetically sealed pots… virtually impossible to clean. Anyway that seemed to cure that problem but I did notice another problem that the customer failed to mention. With the thing on a lightbulb limiter I powered it up into a real speaker load and put 400hz into it. As I raised the volume(s) you could start to see some glow from the limiter, nothing unusual but as you raised the volume drawing more current the limiter got brighter and brighter until at a point the thing just took off on it's own in a flash and the Yamaha's protection clicked in stopping the show. I bring things back down and do it again and this repeats.
Now, not to complicate this but what the heck… I noticed that most times when I would initially power up, the lamps would flash and then extinguish like the SMPS couldn't start. I would let it sit a minute and then the lights would lightly flash on their own, after that happens I could power it up again without incident… most always, that is.
The aforementioned lamps are the level and power LED indicators on the StagePas, not the lightbulb limiter, that's something completely different.
Whadda-U-think? Is my SMPS flakey or is one of the power amplifier modules flakey? or… both… or something else entirely?
Service Manual/Schematic: http://www.go-gddq.com/upload/2014-0...2721337905.pdf
Now, not to complicate this but what the heck… I noticed that most times when I would initially power up, the lamps would flash and then extinguish like the SMPS couldn't start. I would let it sit a minute and then the lights would lightly flash on their own, after that happens I could power it up again without incident… most always, that is.
The aforementioned lamps are the level and power LED indicators on the StagePas, not the lightbulb limiter, that's something completely different.
Whadda-U-think? Is my SMPS flakey or is one of the power amplifier modules flakey? or… both… or something else entirely?
Service Manual/Schematic: http://www.go-gddq.com/upload/2014-0...2721337905.pdf
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