Power Supply

[sguha00]

Hi, I have got an SMPS power supply from Integrated Power Design SRW-65 Series. It had blown onceafter which it was repaired. After repairing for the first time, it blew twice and the faulty component was found to be a zener diode on both occasions. What could be the reason? UC3842 IC is in the circuit.
Thanks,
Regards,

Sumit.

 

[Nigel Goodwin]

Hi, I have got an SMPS power supply from Integrated Power Design SRW-65 Series. It had blown onceafter which it was repaired. After repairing for the first time, it blew twice and the faulty component was found to be a zener diode on both occasions. What could be the reason? UC3842 IC is in the circuit.

ONLY the zener had blown?, what does the zener do?, is it just a crowbar device? - if so I would be inclined to check the ESR of all electrolytics in the circuit, or just blanket replace them!.