TECH: Weird Pacman issue (or I'm just stupid)

Hi All,

I picked up a pac that was "serviced" by Eldorado at some point.
It contained a single chip sync bus controller, however, it had
no markings on it at all, no manufacturer, no device #, nothing.
Instead it had a hand written label that said:
NVC285
REV 0010

What's weird is when I tested it in a known working board,
the board didn't work. Yes, I know what you're thinking, but
the chip is good, as I later learned.

Eldorado *modified* the board to use this chip (details below).

Does anyone know if they made their own replacements?
Or picked some sample/beta chips from Midway's trash bin?

-Mark

In case you come across one, it's not broken, here's the
symptoms and the mod:

Symptoms (in a normal working board):
Shortly (a few 100ms) after power-up, the screen goes
blank and there is NO SYNC (i.e. comp sync is static).

Reason: The SBC chip is stepping on/holding the 1H signal.

Symptoms (in a normal working board, but with the reset switch
held in during power up):
As long as the reset button is held, the screen/sync stays on
(full of garbage of course), as would any normal working board.
As soon as reset is released, the picture and sync go away,
again for the same reason.

Mod to make this work on a stock Pac board:
Bend up pin 2 (signal 1H) on the SBC at board location 6D
Bend up pin 1 (signal 1H) on the LS08 at board location 7H
Connect pin 2 of the SBC to pin 1 of the LS08

That's it.

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Received on Sun Jun 11 18:22:36 2000