Göteborg
If the regulated +12 VDC is low, it might be problem with the +18 VDC (TP8), which is converted to +12 VDC with a voltage regulator LM7812 (Q2).
If the 18 Volt is not correct, it is probably bridge rectifier BR1 / capacitors C6 and C7 that need to be replaced. If 18 Volts is ok, but 12 Volts is not ok, diodes D1 and D2 or voltage regulator Q2 are to be suspected. Check D1 and D2 (DMM in diode position. 0.4-0.6 VDC in one direction, and no value in the other direction.). If these measures ok, then change Q2.
Normal measurements on the testpoints:
TP1: 15 VDC
TP2: 5 VDC
TP3: 12 VDC
TP6: 75 VDC
TP7: 22 VDC
TP8: 18 VDC
Testpoints (resized).png
Centerport, NY
