SMPSU IC explosion... (UC3844)

[Jules Richardson]

lee davison wrote:
>> So, given that assumption for now, anyone know of a likely fault
>> in a typical SMPSU that might cause such a catastrophic chip
>> failure but no other obvious damage?
> 
> The switching transistor has probably gone s/c which ends up
> connecting the rectified mains to the switch output on the IC.
> They tend not to last long when that happens.

Interesting - I suppose in all the SMPSU failures I've seen in the past where 
the switching transistor(s) has gone, it's failed O/C and so nothing else has 
been affected. Can't remember the last time I saw the top get blown right off 
an IC!

At least *if* it's just the switching transistor and this IC that are dead 
then repairing without schematics shouldn't be too hard. Depends what else 
shares the IC output and hence has been given a blast of mains to it...

cheers

Jules