28-05-2013, 08:51 AM
No, the unequal rails just tell you that the current draw on each is unequal, which is not unexpected. Powering an amp with split supplies from a single PSU is asking from trouble. If you only have a single PSU, then you need to make/acquire another one. Or, make a supply divider - just a few transistors (I can show you a suitable design - I made one for work). Quad did this in many of their amplifiers using just a couple of transistors - look up the 306 schematic for an example...
Based on what you've said, the output transistors are probably OK. But I'd want to power the unit with at least 25V per rail first. And for testing with a replacement mains transformer, I'd replace the 4A fuses with suitably rated light bulbs, or use a lamp limiter on the mains side.
Situations like this prove that one can never have too many bench power supplies! A lab PSU should have fully adjustable current limiting and good metering - something like the Thurlby-Thandar PL320 should be the minimum in every lab.
This prompted me to search for the PL320, and I posted details of bargain new units here: http://golbornevintageradio.org/forum/sh...p?tid=3419
All the best,
Mark
Based on what you've said, the output transistors are probably OK. But I'd want to power the unit with at least 25V per rail first. And for testing with a replacement mains transformer, I'd replace the 4A fuses with suitably rated light bulbs, or use a lamp limiter on the mains side.
Situations like this prove that one can never have too many bench power supplies! A lab PSU should have fully adjustable current limiting and good metering - something like the Thurlby-Thandar PL320 should be the minimum in every lab.
This prompted me to search for the PL320, and I posted details of bargain new units here: http://golbornevintageradio.org/forum/sh...p?tid=3419
All the best,
Mark
