PSU voltages high

[kdk]

I've been having problems with my EII not being able to operate the old 5 1/4 in drives and it doesn't have any audio output,  so I just opened it up and checked the PSU voltages.

They are all high, and they drift higher with time. After about 5 minutes, the +5 rail reads +8V, the +15 is over 20, and the -15V is more than -20V.

Oddly, the HxC I installed works fine with the high voltage. I guess it has a build in regulator. Also, the EII is still able to load from the HxC, but then it doesn't make any sound at the audio output.

Any suggestions on what to do next? Would making adjustments to the PSU be possible, or should I have it looked at by someone?

[synthnerd]

Hi kdk,
I have seen similar scenario's with a great number of switch mode PSU's over the years.
The 5V rail is normally the reference voltage used for the regulation of everything else. Don't forget the power supplies switching transformer is just a complicated coil of wire, and it relies on the 5V being roughly right for the other rails to be anywhere close to their proper values. If you have have a problem with the 5V rail, then fix this first and the others should follow. If the 5V rail is putting out 8V, then there is something very wrong with the main voltage regulation system. I would be looking for out of tolerance components, ( as the PSU is not blown and still generates DC voltages then some part of it is working). Replacing all of the Electrolytic capacitors on both mains side and low voltages side of the supply would be something I would do, but the 5V rail should never put out 8V, this could be terminal for the logic of the synth. If you want to play with the PSU then don't leave it connected to the EII, use a dummy load resistor on the 5V rail for test purposes, a high power 3R9 power resistor would be suitable. If you have any problem understanding anything I've said then you should not be doing this... find a good tech where you are and don't risk killing your synth.
Regards,
John.

[kdk]

John - thanks for your reply!

I've got some understanding of electronics, and some experience with soldering. But I think I'll take it by someone with much better skills than I.

I have a feeling the digital side is OK, as it seems to "play" and it can load samples from the HxC, but I'll get it looked at soon.
Thanks!
Kirk