CharlieMax:
The best way to verify your probably correct deduction about a bad
capacitor in the power supply is to take it apart and test it or
substitute a replacement. Also could be a bad diode, bad regulation
circuitry, bad solder joint or something shorted after the power supply
that is dragging down the regulation.
It is all guesses until you do some testing and troubleshooting at your
end.
electricitym
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