Re: IGBTs are pretty fast

"Terry Given" <my_name@xxxxxxxx> wrote in message
news:1139467811.483429@xxxxxxxxxx
you raise a very good point - just how do you "know" that this is
happening. self-interference can be devilishly hard to measure. The only
sure-fire way I have found is with making changes and observing problems
disappear; reverse the change, watch the problem come back. repeat until
convinced.

then examine the root cause of the problem, and resolve never to do it
again.

Yeah, Occam's razor, change one bit at a time and all that...

I think I'm going to put a few turns in series with Lmatch and wave it over
the board, see what starts freaking out. Should be able to find quirky bits
pretty easily and relatively non-destructively.

eventually we tracked the problem down - an intermittent connection
*within* the LM393. a heat gun could make the gate drive turn itself off
and on - the pin concerned was the reference voltage against which the
isolated gatedrive signal was compared. looks like we damaged the bond
wire bending the leg. perhaps 10 times in a row (over a period of
several days) using new chips each time. Hmm.

Weird...

its easier if you just learn how to assemble circuits on top of Cu-clad
PCB. google manhattan method, there is a nice PDF and some truly lovely
examples to look at.

Hmm...

BUT IT'S SOOOO FUCKING UGLY!

what, you think that POS proto-board isnt ugly?

Admit it -- it's better than some gnarly mess entangled through the air. ;-)

besides, what self-respecting engineer trades functionality for
aesthetics?

Doesn't have to be a trade. Look at the P-52, Spitfire, etc.

a lot of consumer gear just doesnt work very well. its not uncommon to
buy things that dont work at all, and nobody is suprised when mall-wart
stuff falls to bits....

No doubt there, but what of 1980s monitors? The kind that are 19" or more
and have BNC connectors for video? I've taken apart a few. Those were the
days when they *cared* to put in perforated aluminum shielding.

Tim

--
Deep Fryer: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms


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