Pacman vertical yellow/green lines

[delroy666]

I'll check on that green signal (*pretends unconvincingly to know how to do that but determinedly resolves to find out quickly*), but I should probably ask your question above again, just in case: If I need to replace 74LS75 @ 3D or the following 74LS157, where is the best place to order these old integrated circuits?

The "Video Green" signal comes out of the Pac-man board at edge connector pin 16, on the bottom (solder) side. Use a multimeter to check continuity between that PCB trace and the "Green" input of the monitor. If your harness is really old, it could be a problem with the edge connector. In my case, my edge connector is brand new, and the problem was with the trace on the edge of the PCB itself.

If that connection is good, start tracing back to where resistors R13, R14 and R15 connect together on the board, which is under one of the daughterboards.

It looks like fellow KLOVer "Riptor" has lots of ICs for sale on his site: http://www.pacmandotcom.com/catalog/8

 

[Riptor]

If backing off that harness got you working I would try cleaning the edge connector. Just this morning I was working on a board that I got from an ops warehouse. It had been raped of many parts and was marked no sound. I repopulated the missing parts and fired it up, played great but low and behold no sound. I started probing around and I determined the sound was reaching the amp so I jumped to the conclusion the amp was bad. Replaced the amp and still no sound! So I started looking at everything from the amp back to the edge connector and found the problem when I wiggled the wires on the edge. The edge connector looked perfect to the naked eye but had just enough of a corrosion layer to prevent connection. A couple strokes with my fiberglass scratch brush and it worked beautiful.

Ooo... just when I'd about given up hope on this darned thing.

I'll give it a shot! Thanks for the info!

Edit: Ok, good Christ. I've been screwing around with this blasted thing for a week and a half. It's been DEAD as a doornail. I cannot believe that it is working now that I have simply backed off with the harness like you mentioned. Still has the green lines and still looks terrible, but it WORKS. Bless you, delroy666!

I'll check on that green signal (*pretends unconvincingly to know how to do that but determinedly resolves to find out quickly*), but I should probably ask your question above again, just in case: If I need to replace 74LS75 @ 3D or the following 74LS157, where is the best place to order these old integrated circuits?

 

[kalevan]

Edge connector cleaning:
Got some time to mess around with the pac this morning. Took a scotch-brite pad to the edge connector for awhile. Reconnected the edge connector socket, and the problem (not working when pressed all the way down, working when backed off slightly) persists. Not a big deal, because at least I can get it working so I can focus on the vertical/diagonal lines again.

New color woes (now red hates me, too):
Before playing, I made some color adjustments and got it looking okay. I played for a short while, but soon the screen flashed red. Now my lines are hued more red than green... or I should say that now I have red lines and green lines. On top of the display, I have a red band. At the bottom of the display, a green one. Everything in-game has a green shadow. See pics... is this a convergence issue?

Trying the board with other monitors:
I have two other machines whose monitors I suppose I could try... if I had a pac to jamma adapter it would be much easier. I need to figure out what I'm doing first, though; I'm afraid I'll plug something in incorrectly and kill something. Both monitors are horizontal. Any adjustments I need to make before hooking these monitors up to the pac pcb or will the game just display sideways with no other problems?

Continuity checks:
I'm getting good continuity between the inputs and the traces for all three colors. I've tossed up some pics so I can show what I'm doing, in case I'm not checking the right spots, but everything seems to match up well.

What's left:
I'm looking into checking resistors, which I will do after I figure out how to read the color bands. Am I on the right trail or am I barking up the wrong tree? Could resistors be causing my problems? I have not pulled the pots to test them as was suggested, because (you guessed it) I don't know how to test them yet, either.

So much more to learn. I have not yet tried connecting different colors to different inputs as was suggested, because I have to figure out how to do that, too. I'm assuming it would involve removing wires from the molex connectors... hehe, don't know how to do that yet either!

 

[kalevan]

Sorry to reply to my own post, but I've just now tested continuity between the green trace and the resistors at r13, r14, and r15. I have continuity on all three, but it only signals audibly on one side of the resistor. From what I gather, this is to be expected, correct?

 

[Riptor]

Sorry to reply to my own post, but I've just now tested continuity between the green trace and the resistors at r13, r14, and r15. I have continuity on all three, but it only signals audibly on one side of the resistor. From what I gather, this is to be expected, correct?

Yes.

The green shadow could be a convergence issue, looks like it. I would test this board with another monitor before doing anything else. Make up an extension cable r/g/b/g/s and run it to another cab if you dont have a loose monitor to swap. Im betting its a monitor problem, not a board problem. If all else fails you can send the board to me and I will test it for you, just pay return shipping.