Re: Pinbot Lamp matrix issues
- From: Jediturtle <jediturtle@xxxxxxxxx>
- Date: Thu, 29 May 2008 05:56:57 -0700 (PDT)
On May 14, 12:11 pm, Jediturtle <jeditur...@xxxxxxxxx> wrote:
On May 6, 7:45 am, seymour-shabow <seymour-sha...@xxxxxxxxxx> wrote:
Jediturtle wrote:
Well, I looked for shorts last night, and couldn't see anything that
could be shorting. I also reflowed all the solder on darn near
everything lamp related. No change. So I'm thinking it's time to
order some transistors and chips and start replacing stuff. Is there
any way to narrow it down further, or should I just start "shotgun"
replacing?
I'd just go ahead and replace the transistors - hold off on the PIA for
a bit.
Also, the weird (ceramic?) resistors for the lamp columns get friggin
hot. I've read this is common, but I don't know how hot is too hot.
They get WAY too hot to touch, and they have blackened the back of the
circuit board. I'm guessing this has to be related, but I donno.
Does that help narrow it down at all?
The resistors do get very hot..... too hot to touch, and they do blacken
the board. That's normal, and probably not the cause of your problem.
They should be 5 watt ones already but double check to make sure.
-scott CARGPB#29
Hurm...so I've done some work, but haven't made any progress. First I
replaced all the TIP42 driver transistors, no change. Then all the
2N6427 pre-driver transistors, no change. Then I went to town on it
and replaced my first 40 pin PIA 6821. Big job, but not nearly as bad
as I feared. Still no change.
I thought I had also ordered the 7408 AND gates, but must have
forgotten to, so I haven't tried changing them yet.
So I will probably order a couple of them soon...anything else that it
could be that I should just order right away just in case that's not
it? Maybe those resistors?
Any help is again greatly appreciated>
Just wanted to close the loop and say I finally fixed this last
night! In addition to what I mention above, I also replaced those
resistors, which also didn't help. Finally swapped the 7408s and that
did it! Everything lights up nice, bright, and at the right time! I
do still have one row out, but I'm sure that's a seperate issue that
I'll tackle next. Thanks to all for the help, especially Scott
(seymour-shabow)! Funny how sometimes it is the very last thing you
try! Oh well...was lots of good board repair experience. My repairs
aren't pretty, though they are getting better, and they seem to work,
so that's good enough for me!
Two valuable lessons learned though this though.
1) Be VERY careful when using a cut-off wheel on a Dremel to cut the
legs off of an old chip. I was being so careful to not hit anything
around the 7408, but I managed to go just a little too deep and cut
through a couple of the board traces! After the panic subsided, I
pulled out the schematics and my continuity tester and set off to fix
it. It took a couple of small wire jumpers to fix what I messed up,
but it works again. I suppose now the board can officially be called
hacked. Oh well..live and learn! :)
2) Double check everything before you solder it to the board!
Apparantly when I ordered the resistors (27 ohm if I remember), the
vendor I got them from had a mixed batch from their supplier and I
ended up getting a few 0 ohm ones mixed in! They looked exactly the
same, but if I would have taken the time to read each number, or
better yet measure them, it wouldn't have been a problem. I didn't do
that, and saw my first flame in a pinball machine with the 2N6427 that
the resistor feeds exploded. Didn't see that coming! So that's what
the magic smoke smells like. The vendor made good on the deal though
and rushed me the correct resistors and replacment transistors, so all
was good.
.
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- Re: Pinbot Lamp matrix issues
- From: Jediturtle
- Re: Pinbot Lamp matrix issues
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