Measuring JAMMA video sync

I have this converted JAMMA cab running Black Tiger (Thanks Pete!). My
trouble is I can't get the monitor, GO7 CBO, to sync to the board. I
recapped it, replaced the horizontal and vertical sync transistors, and
still got no joy. So I started thinking maybe it wasn't the monitor. I
have made sure the wiring between the board and monitor was correct and
didn't have any shorts or breaks. I have one wire running from the sync pin
on the game board, then it is split to go to both the -H and -V pins on the
monitor. I have tried only connecting the -H, or only connecting the -V, or
connecting both of them at the same time with no change. In fact, there is
no difference even if I don't connect any sync line.

I tried to measure the sync voltage at the connector where I plug it into
the -H and -V on the monitor. I get a very small reading like .4 mVDC.
>From the postings I dug up off google, I think that the composite sync on
the JAMMA board is a TTL type circuit, so it should be in the 5 volt range,
and the frequency is about 15.7 KHz. Is that right? I don't have any other
JAMMA boards I can plug in and see what they read. What kind of
voltage/frequency should I be seeing coming out of the game PCB? I want to
verify that the game itself isn't the issue.

The monitor has over-voltage issues that I am working on, so it might be
that too. When I dial the B+ up to 120, I get about 163 volts at the
collector of X904. I still don't know why that is.

Thanks guys.

Sean McLachlan
MIS Manager
LithoFlexo grafics inc.
801.484.8503

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Received on Tue Jul 1 17:33:28 2003