good evening
A similar problem
replaced R76 10 om
Worked for 5 days and burned out
Hmmm.... that suggests nothing is majorly wrong in there if the PSU can work "OK" for a while. But since the same resistor has burned again, perhaps some component somewhere has drifted in value and is causing an overload on that resistor. Or maybe the design was marginal to begin with and so that resistor just burns out after a while when components start to drift in values from age.
OR OR
Maybe there's an intermittent ceramic cap somewhere shorting out... though I don't see how that could happen with the same cap in two different PSUs.
Another possibility is the output CapXon caps going bad (high capacitance perhaps?) It would be interesting to see someone actually check the ESR and capacitance of the output caps to see what exactly is going on.
And if not, perhaps the easiest solution would be to use a big (1 Watt?), through-hole 10-Ohm resistor for R76 and see what happens then. Will the PSU still burn it or will the PSU burn itself?
Given how majorly over-cooked the trace looks in the picture in post #5, I honestly wouldn't suggest trying a resistor rated for bigger power. IMO, that's the same as using a fuse that's larger than what the application calls for... and typically the results can be lots of smoke and sparks when something fails.
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