Ms Pac Man dead. Vram Addresser?

[David P]

hey guys, Father's Day here and finally have a chance to look into the Ms.

I removed the aux board and moved the Z80 to the main board. The response what not what I wanted. I got a high pitch sound from the speaker and a rythmic tic tic tic. The screen is still black.

I'll keep digging. I just hate to buy ONE 74LS74 @8C like Lawnmower says for --Pac-man Board is Dead. No Sync, no Clock.Replace 74LS74 @ 8C. But like you all are saying, it should have fired up, unless the Z80 is bad. Hrm, are the Z80's even being produced anymore?

 

[Riptor]

I have around 900 NOS Z80A's in stock...no worrys.

 

[David P]

Ok I swapped out the 74LS74, but no luck.

The only thing I found interesting (if this makes sense). I removed the aux board and put the Z80 directly into the socket, BUT I forgot to replace the stand-off board that sits next to the aux board cable (Z80 socket). When I forgot to put that board back on, the game DID show some signs of life. It had 3-4 rows of 000000000000 11111111111 going across the screen.

That make any sense to anyone, or am I going to be sending the board out for repair and unfortunately not learn anything? LOL

 

[Riptor]

That really doesnt mean much. The board will not boot without the sync bus card installed.

 

[David P]

Ahh is THAT what that card is. Previously the screen would be totally black (with the card installed). Without the card it at least gives some sort of output. I was hoping that would narrow it down to the card; but that doesn't sound like the case...

 

[Riptor]

The card could be bad, dont rule it out. People have the tendancy to plug that one in upside down and it usually kills it.

 

[David P]

The card could be bad, dont rule it out. People have the tendancy to plug that one in upside down and it usually kills it.

Well, the game was working before it was removed and replaced. I'm sure it was replaced in the correct orientation. A friend does have a Pac-Man. I suppose I could 1. check the orientation, and 2. swap cards into the Ms to see if that helps the game boot. If so, problem solved.

 

[Riptor]

Check the pins on it and make sure none were bent over when it was reinstalled.

 

[David P]

Just so i don't blow something up, is the sync bus card on Pac Man and Ms Pac Man the same? I'd hate to harass someone to borrow their SB card to swap in the game if it's unnecessary.

 

[Riptor]

Its the same for both.

 

[David P]

Thanks! I'll harass my friend's friend and procure his sync bus card and the Z80

 

[David P]

Well hell, this should be interesting. It's something to do with a bad trace, or cold solder. But there are do damn many of them, I have no idea where to start. It also acted like the ribbon cable to the other board, as it reboots when I try to hold the main board side still, while flexing the cable. The problem with that is that the game acted up when I removed the secondary board and put the Z80 in the main socket.

I removed and reseated a lot of the chips on the board, and that seemed to work... for now...

 

[David P]

Ok I know it's been a while, but I've got a semi-fix going. The game boots most of the time, but Ms Pac Man will turn complete Red in color. The ghosts then turn more of a pale color and their eyes are all albino in nature. Oh, even Ms Pac's bow is red, so she looks like a she-devil racing around the screen.

Ideas on where to look for a cold solder, or a bad IC?

 

[Alpha-tron]

Ok I know it's been a while, but I've got a semi-fix going. The game boots most of the time, but Ms Pac Man will turn complete Red in color. The ghosts then turn more of a pale color and their eyes are all albino in nature. Oh, even Ms Pac's bow is red, so she looks like a she-devil racing around the screen.

Ideas on where to look for a cold solder, or a bad IC?

I am think maybe a bad rom socket.

 

[David P]

Too funny. I just finished up reflowing the solder on the RAM chips. I also hit 8A and 8B while I was at it, from something I read about 8B on Lawnmowerman's site.

For now it seems to work, but it was an intermittent problem. The only good thing I can say is that the problem usually crept up faster, and I've had it on for a while playing it, and it's acting normally... Keepin my fingers crossed.

Thanks!

 

[David P]

ARGH! Ok it ran fine fine fine... Then I unplugged it and was playing another game, then I plugged it back in again, and here's what I see... The Ghosts are a bit Pastel in color, and of course the Red Devil Ms Pac-Man (which kinda looks cool). This is of course intermittent.

 

[Riptor]

Either 4A or 7F color prom or a bad 2125 ram or trace to the rams. I would start by replacing the sockets for the proms.

 

[David P]

Riptor... Since the game did a reboot, am I better off looking over the traces to the RAM, or replacing the 4 chips, than looking to the color proms?

 

[Riptor]

Sounds like you probably have more than one issue. A bad 2125 shouldnt cause it to reboot, it affects the colors on the ghosts. Since the pac is red I would lean to the color proms/sockets first.