Re: Measuring JAMMA video sync

-----Original Message-----
From: "Sean McLachlan" <sean@lithoflexo.com>
To: <rasterlist@vectorlist.org>
Date: Tue, 1 Jul 2003 15:33:24 -0600
Subject: RASTER: 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.
>
the Go7 has 2 sets of sync inputs, you should NOT use the sync inputs on the RGB connector - use the syncs on the smaller connector.
(they are inverted)

as for the B+ thing, check the smoothing caps before and after the regulating transister.

c904 - 600/200
c905 - 10/250 (this always leaks)
c511 - 47/160
also change c107 10/250 on the neck pcb, it leaks.

if this dont help then try replacing X904 - it may have a leak.

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Received on Wed Jul 2 07:48:45 2003