Holley 4 Brrl gm ecm

[Chris Conlon]

At 09:19 PM 5/20/00 -0700, Garfield Willis wrote:

>
>>I was using a 749,
>>just tried 2 TBI injectors on one driver P+H, and killed the ecm.
>>No smoke, just stopped firing injectors, but the LED still flickers (in
>>parrarel with injectors),
>>any one gotta clue about that?
>
>Um, sure. The drivers as almost always bipolar devices, that current-hog
>the load, and fry themselves via thermal runaway if they're overloaded
>beyond their design rating. They then become somewhat "high-resistance"
>devices, sufficient to operate an LED load of 30mA or so, but won't pass
>enough current to pull in the injector solenoid.

Now I freely admit that when it comes to anything high power I'm
a mosfet guy, but the times I've fried bipolars (not *that* many)
they all ended up as either dead shorts (which quickly led to) (or)
opens. But, if the driver is a Darlington, it's possible depending
on how it's set up to fry the driven/"big" transistor and leave
the driver/"small" transistor alive. And further depending on how
things are set up (and what pin opens), you could maybe possibly
be able to still drive a LED, running off the driver only.

Anyway... I know this is stretching it a bit. Gar's explanation
is probably right. I was just trying to come up with a possible
explanation that lined up with my own somewhat limited bipolar
toasting experience. (Actually I used to pop little germanium
transistors left and right, back in the day. Hit the wrong lead
and *pop*! Hey, lookie there, transistor guts!)

   Chris C.

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