[s-cars] POS failure analysis

[Igor Kessel]

Mike Sylvester wrote:
> A colleague and I performed a failure analysis on my failed POS.
> 
> 1st we did some non-destructive testing.
> x-ray didn't reveal anything except mildly interesting photo.
> The curve tracer confirmed that ports 1 and 3 were OK and port 2 was open circuit.
> 
> The part was then opened up.
> 
> Inside are 3 FETs or IGBTs potted in some very soft clear material, almost liquid.

Mike,
I am impressed by your scrupulous research. However, I am curious: how 
can you tell a regular bipolar transistor from a FET just by looking at 
the Si substrate with some welded electrodes. To me they all look the 
same, be it a P-N junction or a gate channel.

The reason I am asking is that for years I been thinking on and off 
about replacing the POS with a booster circuit built around either a 
Thyristor, or a Darlington transistor.

Of course, these ideas have never actualy matirialised due to the 
perpetual lack of time and motivation with this relatively newer '97 car 
of mine, whose POS have never left me stranded... yet... so far... oops, 
perhaps I shouldn't have said that... (sez he knocking on Carbon Fibre) =8)

-- 
Igor Kessel
two turbo quattros