On 01/11/2014 15:21, Gareth Magennis wrote:


"N_Cook" wrote in message ...

Surprisingly strong "electrical" smell around the vent ports.
Blown TOP244YN , 20 ohms across rectified mains cap.
Considering crack to its encapsulation is just observable, on one side
only and then under x30. Distorted top to the sillypad (TM) , what may
be a puncture hole at the non-rounded, but then not sharp, rear upper edge.
Hang on a bit , although the tab holding bolt has an insulating washer,
the heatsink is isolated, anti-EMI ?. So if it did puncture , why
leading to failure?
Any known problems with these presumably fairly generic SMPS sub-units,
all else checks out (cold) ok. Mica will be going back in there.






Oops, I just remembered, my TOP chip wasn't "blown" as such, it was
overheating and shutting down.
I rang Peavey to try and quickly establish if they knew of anything that
might be overloading the chip, or was it just the chip.



Gareth.

Going by the curved over top of the sillypad, this has been subjected to
substantial heat. This is not a mixer-amp, just mixer loads of apamps
and a big DSP chip, so why the heat? Vents are either side of the
chassis with no venting local to the smps which is hemmed in between
chassis base and main pcb