Tech: Pacman no video, hot R52

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Hello everyone, hope some one can help.
Pacman was working fine but I turned it on this morning and no video, but
coins up and plays fine. Monitor has neck glow and I can turn up the
brightness to get picture with horizontal lines (normal with no video input)
so I think monitor is fine and this is a board problem. D7 & D8 test ok @ a
little over14vac. D3 & D4 test ok at a little over25vac. Q6 tests ok at a
little over 5vdc from base to ground. R53 is Hot to touch and Q6 feels very
warm for having a large heat sink. R52 is cool but reads 16vdc to ground (
should be about 12vdc ). Could the problem be a bad IR1? Any help would be
greatly appreciated.

Thank you, Paul

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

If game coins up and plays, then we can assume the +5 on the TTL is
fine. Check on a chip to be sure. Check both color PROMs to start,
also reseat the VRAM addresser card, then the funs starts.


Dave

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

"P. Totaro" <PTotaro@comcast.net> wrote in message
news:59GdnYLyiOAAnpDeRVn-hA@comcast.com...
> Hello everyone, hope some one can help.
> Pacman was working fine but I turned it on this morning and no video, but
> coins up and plays fine. Monitor has neck glow and I can turn up the
> brightness to get picture with horizontal lines (normal with no video
> input) so I think monitor is fine and this is a board problem. D7 & D8
> test ok @ a little over14vac. D3 & D4 test ok at a little over25vac. Q6
> tests ok at a little over 5vdc from base to ground. R53 is Hot to touch
> and Q6 feels very warm for having a large heat sink. R52 is cool but reads
> 16vdc to ground ( should be about 12vdc ). Could the problem be a bad IR1?
> Any help would be greatly appreciated.
>
> Thank you, Paul

> If game coins up and plays, then we can assume the +5 on the TTL is
> fine. Check on a chip to be sure. Check both color PROMs to start,
> also reseat the VRAM addresser card, then the funs starts.


> Dave


Hi Dave, thanks for replying. I put in another VRAM board and everything is
fine now. I was having a problem with this board from the start. I traced
the first problem to the Z-80 sync buss card. I replaced that and all was
fine for a few days and than this happened. This time replacing the VRAM
card fixed the problem. I seem to be burning out daughter cards here and
don't know why. R53 is still very hot and voltage at R52 is still around
16vdc. Could I have a voltage problem that is making the VRAM and Sync buss
controller cards go bad? At this point I am afraid to leave the game
on.Thanks, Paul



>
>

 

[Guest]

Archived from groups: rec.games.video.arcade.collecting (More info?)

Voltage at the TTL's is 5.4 to 5.6 VDC Paul

"P. Totaro" <PTotaro@comcast.net> wrote in message
news:596dnZ2dnZ2MYlHEnZ2dnXbSk96dnZ2dRVn-yZ2dnZ0@comcast.com...
> "P. Totaro" <PTotaro@comcast.net> wrote in message
> news:59GdnYLyiOAAnpDeRVn-hA@comcast.com...
>> Hello everyone, hope some one can help.
>> Pacman was working fine but I turned it on this morning and no video, but
>> coins up and plays fine. Monitor has neck glow and I can turn up the
>> brightness to get picture with horizontal lines (normal with no video
>> input) so I think monitor is fine and this is a board problem. D7 & D8
>> test ok @ a little over14vac. D3 & D4 test ok at a little over25vac. Q6
>> tests ok at a little over 5vdc from base to ground. R53 is Hot to touch
>> and Q6 feels very warm for having a large heat sink. R52 is cool but
>> reads 16vdc to ground ( should be about 12vdc ). Could the problem be a
>> bad IR1? Any help would be greatly appreciated.
>>
>> Thank you, Paul
>
>> If game coins up and plays, then we can assume the +5 on the TTL is
>> fine. Check on a chip to be sure. Check both color PROMs to start,
>> also reseat the VRAM addresser card, then the funs starts.
>
>
>> Dave
>
>
> Hi Dave, thanks for replying. I put in another VRAM board and everything
> is fine now. I was having a problem with this board from the start. I
> traced the first problem to the Z-80 sync buss card. I replaced that and
> all was fine for a few days and than this happened. This time replacing
> the VRAM card fixed the problem. I seem to be burning out daughter cards
> here and don't know why. R53 is still very hot and voltage at R52 is still
> around 16vdc. Could I have a voltage problem that is making the VRAM and
> Sync buss controller cards go bad? At this point I am afraid to leave the
> game on.Thanks, Paul
>
>
>
>>
>>
>
>