Re: Star Wars OVERVOLTAGE [fixed]

Thanks everybody for helping me solve this frustrating problem.

Long story short, it was (of course) Q5. Apparently it died at the
same time as the HVT arcing.

Now why didn't I spot this earlier? Basically because I was rapidly
checking so many different components that my test was flawed. I
should have initially stopped to think about how the overvoltage
circuit worked and then tested the components carefully in a logical
progression. Instead, I was just flying through resistors,
transistors, testing voltage regulator voltages and other components
that had nothing to do with the overvoltage circuit. Things I've
read such as "when the HVT fails it ALWAYS takes the BU406D with it"
got me sidetracked into testing and replacing components that had
nothing to do with the problem. (My BU406D was fine).

At one point, I had pulled Q5 and checked it on diode test and it
tested fine. So I put it back in and started looking at other
things. Later, as suggested by another vector list member, I came
back to Q5 and took another transistor out of my "good parts" box and
put it in its place. Still no go. My "good parts" box is supposed
to be parts I have pulled from other HV boards and tested so that I
don't use my "brand new parts" supply unless I have to.

Today, after having decided that it pretty much HAD to be Q5 because
everything else was checking out, I went and found the transistor
that I had initially pulled, and checked it again. It turns out I
was reading the result improperly. One side gave me a 0.600 reading
on my meter. The other side was a 0.060. I took this to be the same
reading (DOH!)

So then I pulled the Q5 that was currently on the board (the one from
my "good parts" box) and tested it - and it gave me only a 0.006
reading on that same leg! So much for my "good parts" box!

Fortunately I had 2 new transistors, and believe me, I tested each
one properly this time. Put one on the game board. IT'S FIXED! No
more overvoltage LED and everything looks GREAT!

For anybody with the overvoltage LED on, I would certainly suggest
checking the overvoltage circuit itself first, and Q5 is the absolute
key to this circuit! If it really isn't Q5 then you probably really
do have an overvoltage condition.

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Received on Sun Mar 28 14:30:45 2004