On Nov 19, 11:50*am, cLx wrote:
Hello,

A day my induction cooking table did not work anymore (an Brandt TI302BS1).
Opened it, saw a couple of IGBT in bridge configuration (two IRGP4068D), and
the bottom one was shorted. Got some spares, replaced the shorted one, power
on : OK.

Two steaks later (in fact, 1 1/2 uses), got some unsuspected shutdowns, and
sooner, the same IGBT shorts again. What I need to check before daring to
replace the transistor and to retry to power on the beast again ?

I've traced a bit the schematics, but it's obviously incomplete :http://clx.shacknet.nu/random/IMG_5802.JPG

And a little picture of the board :http://clx.shacknet.nu/random/IMG_5803..JPG

Thanks !

From memory, shorting a bipolar structure has significance. Like, over
current blows the 'emitter' wire off - OPEN. And, over voltage
avalanches between the collector and the emitter, welding a small
nonsemiconductor material connection - SHORT. Anything that makes you
have an overvoltage, like a snubber circuit, or ?? might be 'killing'
your part. If the esr goes way up on your DC filter cap...?

Plus, I've had too many designers count on the two components to be
somewhat matched, come from the same lot, have similar switching
characteristics. Thus, replace both, each time.

Don't forget proper handling of the component when you replace. Static
discharges, especially during winter months, can be pretty robust May
not kill the part today, just weaken it enough to die tomorrow.