Re: Battlezone - intermittent graphics glitch

I've finally had time to look at this Battlezone pcb again, but I'm not
making any progress in fixing it. The graphics glitch is getting worse;
it's now persistent rather than intermittent.

To be thorough, I installed new vgrom sockets at A3 & B/C3. I also
tried swapping those two ROMS out for a different set. No difference.

I wondered if the problem was in the Y output circuitry. I tried
swapping out the DAC at D9 and the LF13201 at E10. I also replaced the
TL082 at D10. No difference. I checked through most of the components
in the Y-output path without finding anything that was obviously bad.

Any new ideas, anyone? Other than diving headlong into the vector
generator?

Thanks,

Alan

On 2/16/2013 3:08 PM, Colin Davies wrote:
> I'd look at the counters/timers and other maybe logic in the vector
> generator...
>
> Not sure if a Dodgy Eprom Sockets in the VGROM would cause that...
>
> I've got an Asteroids that slopes up like that too.. Not had a chance
> to look at it !!
>
> Regards, Colin
>
> ----- Original Message ----- From: "Total Impulse"
> <totalimpulse@comcast.net>
> To: "vectorlist" <vectorlist@vectorlist.org>
> Sent: Saturday, February 16, 2013 6:18 PM
> Subject: VECTOR: Battlezone - intermittent graphics glitch
>
>
>>
>> I'm working on a Battlezone board set. It has an intermittent
>> graphics glitch - lasts anywhere from a fraction of a second to a few
>> seconds in duration at random intervals. When it goes "wonky", the
>> vector endpoints in text spread apart and the lines of text angle
>> upwards and become distorted.
>>
>> Photos here:
>> https://picasaweb.google.com/108339843851140624101/BZIssue#
>>
>> Before I start digging into it, any suggestions on likely areas to
>> check first?
>>
>> I've already replaced all the electrolytic caps, the adjustment pots,
>> the header pins for the interboard cable, and any obviously poor
>> condition sockets. No faults come up in self test mode.
>>
>> Thanks,
>>
>> Alan
>>
>

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Received on Sat Apr 13 19:31:16 2013