Power supply outputs random voltage

[uliano]

Suddenly (after maybe some year of NON use) this old PSU got crazy

Often, but non always, more likely on channel 2, the voltage under load is less than programmed even if the drained current is far less than the preset limit.

I have no idea where to start looking to investigate this problem.

Some explicative pics.

[wraper]

Your electronic load could be oscillating. Try adding say 1000uF cap to PSU output.

[uliano]

I didn't think it was the case as the problem showed up with a real (and very small) load, however



What is worst is that it doesn't even need a load

[Ice-Tea]

If memory serves (and that's by no means a guarantee), the polarity protection diode on the outputs is a weak point in these supplies. Wouldn't hurt to check. YMMV, obviously, but it doesn't hurt to check...