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8770A, power supply problem: ITT PowerSystem PEC 3959 rev K

Question asked by Tardz on Oct 28, 2017
Latest reply on Nov 13, 2017 by thysell


I have an arbitrary 8770a generator that worked very well, but suddenly it broke down. The problem is the power supply and it is really big. I did some basic tests:
- no fuse blown
- no short circuit on the power lines
- the power supply lines comply with the impedance specifications
- all internal power resistors have good values
- all diodes tested are good
- no transistor short circuit and are tested OK
- no electrolytic capacitors tested were short circuits
- thermistor, varistors and overload protection circuits are OK
- when powering up, DC input voltage was correct
- no damaged components or PCBs


The source of the failure is probably the controller or the monitoring circuit, there are many integrated circuits, but without a schematic, it will be very difficult to find the source of the problem. I have the electrical diagram of the 8770a except that of the power supply. So I'm looking for this schematic without much hope unfortunately, it's from ITT PowerSystem, PEC 3959 rev K ... if anyone ever has a copy available it would be really good.


Thanks !