1.Bad mounting of the device, so it works on a higher temperature than it would be optimal.
2.Voltage spikes.
3.Bad general design of the IC.
Is there a way to find out which one applies here?
Measure the actual temperature.
The one which we have in the washer is heavily modified for better cooling, and I can not undo it without much damage. And of course I am not sure if this board is affected as well so we would have to measure one it in a board which is definitely known for this problem.
These IC's are built to a cost point and end up being a bit fragile, running 24/7 in many applications and subjected to mains transients.
The power mosfet and current rating are sized to the micro penny. Look at die pictures of LNK306GN , similar TOP250YN also shows the family of parts are just scaled up.
Thanks for linking this topic! Amazing pictures, wanted to start to look for such pictures for a while.
Did anyone untill now pointed out the exact part which may be the culprit? The 306 should be similar to the 305, but I think both are falling like flyes.
These are although connected to the 230V 24/7, but the actual working hours where they have to work at their rated level are very low numbers, like few thousend hours, so maybe not the power mosfet is the problem?
Anyway after the top of it is blown away, is it still possible to do an autopsy to point out the exact part which failed? I don't have any blown one by the way.
It's possible the device could be sensitive to excessive input ripple, constantly shutting down and restarting every cycle. Filter caps will likely be the bare minimum and not the highest quality parts.
I wish someone had a programmable surge generator with relative low energy level, and a high voltage scope probe to test what kind of voltage spike would cause any damage. But we don't know anyone with such equipment do we?
By the way I just checked the website of the manufacturer Power Integrations, and now they seems to have a new series with number 2: like TN2 series of TN, or XT2 series instead of XT.
There is a small difference even in the schematics.