"cLx" wrote in message
...
On 20/11/2012 20:24, Franc Zabkar wrote:
On Mon, 19 Nov 2012 19:50:17 +0100, cLx
put finger to keyboard and
composed:

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

I don't have any experience with these appliances, but my approach
would be to replace both IGBTs and all the capacitors, especially the
two 0.68uF film or polypropylene (?) types.

Thanks for your advice. It's polypropylene caps I guess. There is a
picture :
http://clx.shacknet.nu/random/IMG_5956.JPG
Any recommended source ?

I'll also change the two "snubber like" 47nF MKP capacitors (mounted from
the
common node of transistors and coil to both supply rails).


I'm with Franc on this. Replace both devices and all caps near them.

IGBTs are my least favourite power switching devices. I've always found them
hugely over-priced compared to FETs, and extremely fussy about their
operating conditions. I have also been told by a friend of mine that works
with them a lot, that they are *extremely* intolerant of having their gate
terminal touched when they are not in-circuit. He says that they can be
damaged as a result, so that's maybe something else that could have been a
contributory factor in the device re-failing.

Arfa