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Can you hear game sounds when you coin up?
Im assuming these are the chips i need to replace ?This is from http://lawnmowerman.rotheblog.com/#basictips
No Vertical Sync - lines and colored block out of sync. No game play.
Replace 2R & 2S (74LS161)
Main page: http://lawnmowerman.rotheblog.com/
You probably already know about this page, but just in case. Lawnmowerman's page is awesome for Pac-Man repair tips.
Also, basic stuff that often works:
- Super carefully remove and then replace all socketed chips to re-seat them.
- Look for burned areas on the edge connector contacts.
- Visually inspect the edge connector (burns, bent contacts, broken wires at the solder points).
- Check across one the big caps (C2 or C3) to see if you have good 5VDC.
- Inspect all electrolytic caps: signs of leaking? bulging? electrically good?
Those could very possibly be the problem. They are the ones mentioned on LM's page. Can you check to see if the chips have 5V on pins 16? Do you have an O-Scope? Probably should download the datasheet too.
But, be sure to try all the easy stuff first! I wouldn't desolder chips until I was sure it was necessary.
I am getting a solid blue screen now. I have no idea how i have been very careful. I'll go ahead and check the fuse block again.That seems like a solid clue. Something may be pulling the voltage down on the board, but it may or may not be these chips. You may be looking for a shorted component.
Are any the chips on the PCB hot to the touch (like they're shorted and pulling way too much current)?
You may try to remove all the socketed chips (with the game off of course) and then turn it on and see if the voltage comes back.
Also, be sure to check that you're getting a solid ~7VAC coming in. Don't forget to check the contact integrity of the fuse clips. Remove and re-seat all the fuses.
Bad contact at the fuse clips (or at the edge connector) will create a high source impedance situation. The voltage will look OK unloaded, but will be pulled down when you connect a load.
Looks like you need to set your hz and vert holds and maybe turn down the blue.