SW Vector PROM problem

I picked up a "tested and working" Star Wars board set on EBAY in hopes
that I could bring it with me to look at my friends ESB problems I
mentioned a few weeks ago... It arrived playing blind (spot killer on) -
so I swapped in a known working AVG board and the game came up with a
picture. Now it has no starfield (in attract and game) and no ties
fighters when played with a tiny death star in the middle of the
screen. Test mode comes up with following Matrix Errors:

NNNF FNFN 0000
NNNF FNNF 0000
NNNF FNNN 71C8
NNNF NFFF CA48
NNNF NFFN 2D16
NNNF NFNF 1FC2

After searching Google for SW matrix error posts I found a thread where
Greg Woodcock talked about my exact problem and that it is attributed to a
bad vector PROM on the CPU board - chips 136021-110 thru 113 (not sure
which one). Since I still had all the old chips from some previous ESB
upgrades, I swapped all four PROMs (at the same time instead of one at a
time). The game came up working normally during attract mode and during
play of the tie fighter wave but when the next wave started all went
blank. It appears that the PROM blew again. The board now works like it
did before swapping the PROMs.

Here's the questions:

1. What would cause the PROM to blow / fail ? I'm pretty sure the sockets
are OK

2. What should I try next to narrow down the failing part?

Any help is appreciated

Regards,

Steven Winslow

At 11:07 AM 11/6/2003 -0500, you wrote:
>I had a Tempest that would do this. The watchdog circuit on the monitor
>had a problem. I replaced the monitor because I was in a hurry (and I
>could), but that was what was wrong.
>
>-Al-
>
>
> > Hello Everyone!
> >
> > What are your thoughts on a Star Wars ESB that works just fine in
> > attract mode but blanks out when you try to play a game? A friend of
> > mine has one that has just started doing this and has asked me to come
> > over and take a look at it. Don't know what it does in test mode yet.
> > What are the common faults for this symptom ? Thanks for your help
> > ....
> >
> > Regards,
> >
> > Steven Winslow
> >
> >
> >
> > ---------------------------------------------------------------------------
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>
>
>-=-=-=-=-=-=-=-=-=-=-=-=-
>Visit Al's Arcade
>http://www.alsarcade.com
>-=-=-=-=-=-=-=-=-=-=-=-=-
>
>
>
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Received on Sun Nov 30 00:56:01 2003