tech: centipede will not sync

[Larry]

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

i have a centipede pcb that will not sync. monitor is 100% and all the volts
are correct on the power supply and everything checks out fine so i know its
the board. any suggestions where to start would be great

 

[Guest]

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

Did it sync at one point? Is it set to positive sync?

"Larry" <lmagrie2@comcast.net> wrote in message
news:L5ydnWTOo574WSHfRVn-1g@comcast.com...
>i have a centipede pcb that will not sync. monitor is 100% and all the
>volts
> are correct on the power supply and everything checks out fine so i know
> its
> the board. any suggestions where to start would be great
>
>

 

[Larry]

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

when i got this machine it would sync after about 5 to 10 minutes but it
would sit half way up the screen
"Jason Souza" <jsouza@verizon.net> wrote in message
news:Q54ve.93$At6.32@trndny09...
> Did it sync at one point? Is it set to positive sync?
>
> "Larry" <lmagrie2@comcast.net> wrote in message
> news:L5ydnWTOo574WSHfRVn-1g@comcast.com...
> >i have a centipede pcb that will not sync. monitor is 100% and all the
> >volts
> > are correct on the power supply and everything checks out fine so i know
> > its
> > the board. any suggestions where to start would be great
> >
> >
>
>

 

[Guest]

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

"Larry" <lmagrie2@comcast.net> wrote in message
news:L5ydnWTOo574WSHfRVn-1g@comcast.com...
> i have a centipede pcb that will not sync. monitor is 100% and all the
volts
> are correct on the power supply and everything checks out fine so i know
its
> the board. any suggestions where to start would be great

If you're trying to use negative-going composite sync, as most games do, I'd
say the problem is a bad 7407 TTL chip located at A9. I've run into that
before.

But if you're using positive-going vertical sync and horizontal sync, those
are provided on the board, too. Those come from a 7407 at location A/B10.

That should take care of your problem.

HTH,

Matt J. McCullar