Pac-Man that constantly goes down.

Peale

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Not mine, nor do I have access to it.

So, I used the multimeter to measure the pins on the 74LS chip responsible for joystick movements.

I found the pin layout (if that's the right term) for the 74LS367 chip responsible for up-down-left-right. I also found this great site (http://lawnmowerman.rotheblog.com/logicprobe.html) that basically lays out how to measure it.

I used my schematic and found that pins 14 to 13 are responsible for Down on the 74LS chip at location 8E. I also learned pins 10 and 9 are responsible for Up. Basically, I measured the voltage between pins 14 and 13 and found they were always at 4 volts (I had my multimeter set to AC10V). Pins 10 and 9, 6 and 7, and 4 and 5 were 0. I then measured pins 10 and 9 while the up switch was depressed and it read 4 volts. When turned off, it went back to 0. So pins 14 to 13 are always on. What does that mean? Bad 74LS chip? I also learned R45 and C20 are the resistor and capacitor responsible for down, respectively (220 ohm, .1 microfarad). I have no clue if the Res. and Cap. are contributing to the problem.

He replaced 8E and its still doing it. I told him to check out the other chips that relate to this, but he's having trouble reading the schematic. Any ideas?
 
Try replacing the .1 cap. I have seen those go bad on more than one occasion and will cause the line to go low as if your activating the joystick in that direction. Its very unlikely that the resistor is causing any probs.
To do a quick check you can just snip one end of the cap and if your problem still exists just solder it back down.
You said he already replaced the buffer (LS367) so really not much else it could be. Maybe try unplugging the control panel and make sure the switch itself is not stuck. Actually I was assuming he had checked the obvious before diving into the board but.......
 
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I've seen bad resistor packs on those boards as well. Especially those damn flat ones you also have problems with on Galaga.

The resistor packs tie the lines high (to +5v) and if they are bad the lines will be floating.

RJ
 
I don't know the answer to this but the title of the thread would be more humorous if it was a Ms. Pac-man.
 
I don't know the answer to this but the title of the thread would be more humorous if it was a Ms. Pac-man.

Damn, I usually pick up on things like that...good call.


Yes, definitly inspect the resistor packs too.
 
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Hello there! First, my gratitude goes to Peale for introducing me to these forums.

Now to the good stuff. My resistor packs RM7 and RM8 look solid. I know the specific resistor and capacitor responsible for the down direction is R45 and C20. according to the original Ms. Pacman manual (which came with the machine).

I have tested the game with the down direction (the top switch) disconnected, and also with the entire control panel's molex disconnected.

Which capacitor do you specifically suggest I disconnect? Location wise? The C20 one? Thanks a lot for the help.
 
OMG! It worked! The capacitor C20 is cut and she runs! Like the real thing! I mean... heck, it is the real thing! Woot! Original 1981 Ms. Pacman up and running. A 20 year dream completed.

Do I still need to replace the C20 capacitor?

Also, I'm noticing *slightly* too much read on the first two stages which gives the maze walls a sort of pseudo-3D effect by bleeding on the top and right side of each wall segment. I assume this is not intended and I should reduce the color via the monitor controls.
 
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.1 uf 50v axial cap. Not sure if radio shack carries them. If you have any junk boards laying around just about any arcade pcb should have plenty you can snag.


http://www.radioshack.com/product/index.jsp?productId=2062365

Adjust the red down on the monitor neckboard pot. Your only seeing it on the first two levels because of the colors of the maze.
 
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All done. Everything's in working order. Coin door lights completed. That was a lot worse than I expected it to be. Anyway. My last project will be to perhaps wire a difficulty switch for the difficulty jumper located on the board and add a sound switch somewhere.

Thanks for all the help. That was awesome/nuts.

finished_pacman.JPG
 
Here's a weird question (and possibly a dumb one):

I have the normal speed and fast speed chip for 6F. I have the fast speed chip installed currently. Is there a way to perhaps create some sort of setup that will allow me to toggle between the two chips? I heard of the 4-in-1 chip, but that also includes cheats.

Any thoughts?
 
I dont think the earlier version of 4-1 has cheats. I have the files for it if Jason doesnt have them on the site anymore.
 
If you could give me the file that would be great.

Also, would I be able to create my own image to burn to an eprom? There are some tweaks I would like to make, but I don't know if they're possible.

Stuff like making the game play sped up by default and going back to normal by pressing a button. And perhaps having the invincibility cheat be available but only by pressing something more complicated like P1, P2 and right at the same time. Etc.
 
Ms Pac boards are Pac-Man boards with modifications. There are instructions on Souzilla's site with everything you need to know.
 
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