8 Dec
2005
8 Dec
'05
8:20 a.m.
Tony Duell wrote:
Until now :)
Tony Duell
wrote:
I must have been lucky... all the ones I've had
to fix before have had failed
in other ways...
You have been very lucky. Random
failure of the weekend was a UC3844 IC in a switchmode power supply -
with a very loud bang, the entire top of the chip blew off, but there's no
*obvious* sign of any other failure within the supply.
This deos not mean there
are no other component failurs. This sort of
thing is very common actially. I have never had a chopper transistor fail
open-circuit.
casualties so far are both choppers (IRF740's), the UC3844, and a couple of
resistors (they were hidden by the heatsink before; rather obviously cremated
now I've removed it!)
The UC3844's current sense line got a blast of mains down it which is what
killed it...
I'll test other components in the area though in case they've failed with no
visible effects.
cheers
Jules