Tac/Scan problems

Hi all..

 We have a Tac/Scan here that we are trying to get going in time for a
mini-meeting in the uk, .. I need some help, if anyone can be bothered :)
I've done lots of work on 6100 and G05 stuff, but never touched a G08.
Here's the problem:

- machine worked fine for a while, game, sound, monitor, everything.
- game started resetting, burned out +5v connector
- connector replaced, game ran for aout 2 mins.
- sat for 4 months in storage
- plugged back in, +5v is 0.1v, all other voltages are ok..
- replaced regulator (ua723) no difference.
- gave up, took advice and wired in a pc power supply for the +5v, but used
original Linear supply for all other voltages.
- The game now runs, and the monitor now runs too, but i have graphics
glitch :

here are some pics :

http://www.andys-arcade.net/Dcp07427.jpg
http://www.andys-arcade.net/Dcp07428.jpg
http://www.andys-arcade.net/Dcp07429.jpg

you can see the game running, coin it up and play it, the sound has
knackered now tho, but that might be something unrelated, not too worried
for now.

it looks like the pcb is shunting the beam around to the correct locations,
but not sitting around and drawing the graphics, instead it stops and sits
creating a spot... also, there is a nasty bright dot in the middle anyway...

has anybody seen this problem before? If i could just isolate it down to
which pcb in the cage is bad that would help a great deal, we have a spare
boardset, but it seems to be pretty much completely dead.

My thoughts were it has to be a math problem, not a monitor problem, not a
bad dac, or bad op-amps, has to be something before that...

anyway, i'm babbling, if anyone can help, let me know thanks..

Andy Welburn
www.andys-arcade.com

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Received on Fri Jan 31 11:43:37 2003