Hello and asking for help with HP 67 power unit

[teenix]

There is always the chance of a defective passive component like a capacitor or resistor especially since they are approaching 50 years old.

There are 3 capacitors in the power supply which may cause problems if they are failing, but are cheap to replace.

If a chip has gone, your only option is a replacement board or replacement part if one is available.

The only real way to explore the problems is with an oscilloscope to see what signals are circulating around the board.

cheers

Tony