[mole42uk]

Hello Richard,

I am working on the pre-regulator because that is indicated in the Service Manual as the next section to check after the AC mains rectification. Tonight I found an o/c 2µ2 tantalum and two s/c diodes in the circuit that derives power to the 3524A from the transformer when the chip is running.

I can see that the 3524A has a typical SYNC output on pin 3 but nothing on pin 11 or 14 which, from my understanding of the datasheet, is because the voltage on the shutdown pin 10 is too low. Because I see a SYNC output I think the 3524A may be okay. I have several 3524 parts in my spares box which might serve to prove the remainder of the pre-regulator circuit.l

I think there are a few failed parts in this supply and I'm tracking them down part by part using low voltage test supplies until the measurements start to make sense. I am fortunate to have another similar supply which also does not work but allows me to cross-reference. When I have the first one working I'll fix the other as a spare.