GI Dimming - RESOLVED

On Sep 5, 11:03 pm, martin <martin.reyno...@xxxxxxxxx> wrote:
On Sep 5, 7:39 pm, "John Wart, jr" <johnwar...@xxxxxxxxxxxxxx> wrote:



On Sep 5, 10:25 am, "John Wart, jr" <johnwar...@xxxxxxxxxxxxxx> wrote:

On Sep 5, 10:10 am, frenchy <mf101...@xxxxxxx> wrote:

So did you replace the 339 yet? I had two games where thedimmingwas
screwy or dead on all strings and both cases it was the LM339.
What does the LM339 do anyway, if it's some kind of bit logic that's
counting the levels, maybe some bit(s) in it are dead so it can't do
some of the levels with that bit in them.

I have replaced the LM339 and have buzzed all the traces out on both
sides and all are intact and solid.

I removed SR1 and verified the value of the resistors.

I am tempted to replace the ribbon header - not because I think it
needs it, but because I want to rule it out. I've studied the
schematic, the theory of operation, and I still have not figured it
out yet. I *will* find the culprit though!

Did some more testing tonight.

Pulled the resistors in the zero cross circuit and verified their
value with my DMM.
Replaced resistors, resoldered.
Swapped a TRIAC out with a known good one off a working board (just 1
triac)
Ohmed out all the traces again with the DMM in the zero cross
circuit / U6 / U1
Replaced the ribbon headers, just in case there was a flakey
connection.

Same result

Gonna keep on keepin on, but if anyone has any ideas, I'm all ears :)- Hide quoted text -

- Show quoted text -

The signal starts with eth AC line in, gets converted to a square wave
by the 339, and winds its way to the ASIC chip on the CPU. A logic
probe should flash all the way back along that path to the 339. So I
would start with that.

For some reason, I can't reply to my original message through Google.

This turned out being an outbreak of dumb*ss on my part.

J115-1 was supposed to go to ground, and the pad was completely burnt
off the board. I didn't look at the schematic or another board while
replacing the connector, just did the 'continuity checks' recommended
on the WPC repair guide. Had I looked at the schematic as well, I
would've noted that it needed to be connected.

Now that it's connected, it works great!

Thanks for all the suggestions and help from the group!

--john



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