Hi guys,
I'm trying to repair a broken Lodestar 8203 Bench Power supply and I was hoping to ask the hive mind for advice for my next step.
So here's the summary:
It's a Lodestar 8203. It's old-ish... I believe early 00's. However the good news is that I have an operating manual complete with circuit diagram!
The Slave channel failed, so I opened it up and found a vaporised trace on the main slave PCB. I suspected the bridge rectifier so I removed it (and it was shorted closed) so I replaced it, repaired the PCB trace and replaced the fuse.
Now it powers up but the slave channel reads -0.5V and the voltage adjustment has no effect.
So I'm guessing that the shorted bridge rectifier has damaged some components downline. I suspect the 2N3055 power transistors might have been cooked, so I took one out and tested it and it appears ok- but I might replace the others anyway.
So I was wondering if someone might be able to suggest a likely culprit or at least the next component to test?
FYI the failed bridge rectifier is D1-4 on the main circuit diagram.
Any suggestions would be very much appreciated - it's a good unit and I'd love to repair it rather than tossing it out.
Many thanks, Dom.