Surface Mount Components

[J. Creech]

First off, Thank You Gwyn  and Gar, you have both been most helpful.

<snip>
I wonder if the toasty components are capacitors or not. Not sure why the
failure of the electrolytics would cause the smaller caps to burn - unless
the big caps were limiting voltage spikes and the working voltage of the
small caps was substantially exceeded.
<end snip>

Well, it was inked on the board "C104" and "C107", so I can only assume they
meant capacitors go in these slots. As for why they are fading away, you
pretty much hit the nail on the head as to the reason. This problem, ( of
the electrolytics leaking ) is a fairly common one on DSM's. Ask just about
any owner of one, and unless they've been living in denial, they'll tell you
all about someone they've heard of in this "predicament".

<snip>
Any chance to find a good unit to be inspected for the
markings on the dead components?
<end snip>

Yes, I have 2 other (non-EPROM) ECU's. Pretty much identical, except for the
EPROM and it's related tracings. They are unmarked as well. All of the SM
resistors on the board are marked, as well as slew's of SM
Transistors/Triacs.



<snip>
The best thing to do is to see if you can isolate the
device (ya know, one lead/trace/side open), and MEASURE the C with a
meter that can do so. If they're toast to the point where you cain't
measure them, well then you're toast too! If you can get a decent
measurement that looks right, but their metal ends are eaten by
corrosion, then replace with same value.
<end snip>

Gonna try this, as the main thing about the caps is, like you said,
corrosion. Although, they are kinda darkened on one end, I assume from the
excess heat they've had to endure. One of them ( the one mounted to the bad
trace ) has one end so badly corroded, that I was only able to get an area
about .010" in dia. to tin up again. The main problem here will be obtaining
a Capacitance meter. I *think*  that I have a friend that has one.

Again, thanks a lot guys. These questions I had were one's I've been meaning
to find answers to for some time, just never had the "opportunity". I've
kinda shied away from the SM stuff, my hand is so shaky sometimes that it's
hard to do the fine work required to deal with them. But, this EPROM ECU
I've come into possesion of, well these are hard to find, and pricey to
boot. I've wanted one so I could have the modifications that Technomotive
offers for these cars. I know, I know, not exactly diy-efi, but this car
isn't really my diy project.

Scott Creech

Forewarned is Forearmed

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