I have a Soundcraft Series 800B that is powered using a TS24 PSU. I was noticing there was a bit of noise on my input channels whenever I switched on the Phantom Power, so I decided to measure the phantom power voltage. It's measuring about 67 volts, and so I'm assuming that's the reason for the noise.
I've never troubleshooted a psu before and can't seem to find a schematic for this particular psu. I'm guessing the problem is a faulty transistor, and was considering just replacing all 6 transistors in the 48V circuit. Is this a reasonable course of action, or is there a better way for me to do this?
Also, Does anyone know what purpose the variable resistor serves? Is it part of a voltage divider that sets the output voltage, or is it used to bias one of the transistors?
Thanks,
Joe