Hello and asking for help with HP 67 power unit

[Tapti]

Dear Experts,
thanks a lot for your help so far. Today I made measurements of the two supply voltages Vss and Vgg, which should be around 6.25V and -12V, respectively. With the damaged board I measured 6.2V and -10.1V. While Vss should be fine, Vgg is some 20% to low. I'm not shure that this somewhat lower voltage may be a problem. But when I compare the values with those taken from my second (good) board, giving 6.35V and -12.1 Volts, there is in fact a significant difference. When I'll get some time tomorrow, I will repeat the measurements with an oszilloscope to look for the amount of ripple on these voltages. For the moment I'm still hoping that repairing the power converter might solve the problem. On the other hand of course it is also possible that particularly Vgg has to deliver to much current. Perhaps do to some short within the electronics being supplied with Vgg.
I'll keep you informed,
Stefan