Ms. Pacman help

mzider

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Just got a ms. pacman which is my first arcade game. Game turns on and plays and monitor comes up but picture is not right.

I adjusted horiz. and vert hold as well as the pot for the slanted screen on the bob roberts site. This left me with the ability to see rough blocks of the ghosts and pacman. Pacman stays in the lines of the maze and the joystick moves the pacman block in the correct direction2. There is no clear maze or dots.

My first question is whether this is a monitor or board problem? I am thinking its a board problem but am not sure as i haven't adjusted a monitor before. If it is a board problem what is the best place to start?

I believe monitor is a 19K4600. Game also resets randomly during play but i am thinking that is either the edge connector or fuse block which i plan to replace.

Thanks for any help.
 

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Looks liek a board problem at least. You wouldn't have thast many zero's going by if the board was running okay. Try cleaning and reseating all your socketed chips and daughterboards...
 
Its a board problem AND your monitor is out of adjustment. Dont mess with the monitor until you get the board working as its good enough for troubleshooting.
If you need to purchase a working board send me a private message.
 
Had time today to remove all the chips and clean and reseat them. This caused the blocks for the ghost and ms pacman to be rounded out but now became the wrong colors and ms pacman seemed to be upside down.

Starting to think this might be a bigger project than i hoped. A few of the roms don't look original and part of the board has chips added to it( in the 7S 7R and 7P positions). They are jumpered to the Vblank, 128V, and Flip signals and seem to output a new Vblank to 8S (which outputs the IRQ) i think haven't drawn out the schematic yet. Is this some kind of hack?

One thing i tried was to put the game into self test and then adjust the monitor. Was i wrong in thinking self test is a separate section of the board? I could still not get it adjusted.

Fixing this up as a present and i would really like to get this board working.

Any suggestions?
 
Well, first verify that all your chips are in properly with no bent legs or backwards chips.

I was recently working on a Pac board that had blocks around the characters and a funky looking Pac-Man.

The blocks went away by replacing the chip at 5E. The funky Pac character went away by replacing 5F...
 
The game will still boot up with bad 5E/5F roms. You have garbage screen so you need to look elsewhere. How many roms do you have in row 6? The board may be modded.
 
Starting to think this might be a bigger project than i hoped. A few of the roms don't look original and part of the board has chips added to it( in the 7S 7R and 7P positions). They are jumpered to the Vblank, 128V, and Flip signals and seem to output a new Vblank to 8S (which outputs the IRQ) i think haven't drawn out the schematic yet. Is this some kind of hack?

Hardware speedup hack... makes the irq run at 120Hz instead of 60Hz, so the game plays twice as fast.
 
I reseated all chips including Z80 processor and now have the following picture. Maze is still messed up but all characters are crystal clear. Could it be a video ram problem? Is the maze on a seperate rom that could be bad? Trying to find a similar picture on the arcade game over site but nothing looks similar.

I figured that was a speed hack. Thanks for confirming it.

In row 6 i have 4 roms (6E 6F 6H 6J) also have the 5E and 5F roms. I think that is the original setup right?

Any new suggestions?
Thanks,
Matt
 

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Bad connection / broken traces around the vram addresser.

I finally got a chance to mess with the game again. I wiggled the Vram addresser board and sure enough the picture snapped into focus. This made the game playable but i think the monitor needs a cap kit.

Unfortunately it only worked for a couple days. One night i was adjusting the volume and the screen just went black. I didn't notice anything strange while adjusting the volume pot but now the board wont do anything.

The board is getting both 7.5AC lines. The ground is good, the voltage across C2 is 4.9VDC. No fuses popped. What could have happened? Anything else i should check?

I am so frustrated because it was working and now nothing...no sound no picture (although monitor neck still glows so i know its not the monitor.)

Any ideas?

Thanks for everyone's help so far
 
My Ms Pac I just got refused to boot... wouldn't coin up or anything. I just grabbed a spare switching power supply and ran +5, +12, and GND directly to the boards, fired right up. I was getting correct voltage to the board from the connector 7.5VAC, etc etc... but the board just refused to do anything besides make a humming sound in the speaker.

Might be worth try'ng if you're interested in going that route.
 
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