"senator richards" wrote in message
...
I am trying to troubleshoot a small SMPS that came from an A/V
switcher. Input is 120vac and it is supposed to output + and - 15vdc
at .8A. Currently it is outputting +17 on one output and somewhere
between +22 and +30 on the other output. My experience with SMPS has
usually been shorted rectifiers or bad output filter caps so the first
thing I did was check all the diodes and replace the output caps.
Obviously that didn't fix the problem. The high voltage is about
170vdc. The supply to the pwm chip is fluctuating between 7-15v, so
i'm thinking this might be the problem, but maybe its something else.
In case its not obvious, i'm fairly new to tinkering with these
things. Thanks in advance for any help.

Randy

The cap that filters the supply to the pwm chip on the primary side, maybe ?
It's pretty common on most designs of switcher. Work on the thing on an
isolation transformer if at all possible. They are potentially very very
dangerous if you are not fully competent with them

Arfa