Ms pacman no boot/someitmes boot

[djhurt1]

Hello,

Excited to be admitted to the forum! I joined because I'm having a heck of a time with a Ms. Pacman cocktail I recently acquired. It was working perfectly fine before I started mucking with it sadly. It had the high speed chip so I removed that and replaced with one from highscoresave.com. Unfortunately after powering back up, I get a screen full of random text characters and graphics. I then got an original chip for the 6F thinking perhaps I got a bad chip. Same result. I did notice someone had previously flowed solder across the edge connector on the main board so I reflowed the solder again. Same result except sometimes I get a screen with some alternating characters and graphics with occasional random beeps but it's not consistent. Usually just the frozen screen mentioned above. I did however notice that one connector on the ribbon cable for the auxiliary board has a pin missing. I didn't think I lost a pin when I disconnected it but perhaps that's what happened. Does anyone else a pin missing on their auxiliary board ribbon connector? One last thing I tried was take the z80 chip and seat it directly on the mainboard. Same result except the screen gets wavy. Any thoughts or guidance would be appreciated!

 

[mecha]

Hello,

Excited to be admitted to the forum! I joined because I'm having a heck of a time with a Ms. Pacman cocktail I recently acquired. It was working perfectly fine before I started mucking with it sadly. It had the high speed chip so I removed that and replaced with one from highscoresave.com. Unfortunately after powering back up, I get a screen full of random text characters and graphics. I then got an original chip for the 6F thinking perhaps I got a bad chip. Same result. I did notice someone had previously flowed solder across the edge connector on the main board so I reflowed the solder again. Same result except sometimes I get a screen with some alternating characters and graphics with occasional random beeps but it's not consistent. Usually just the frozen screen mentioned above. I did however notice that one connector on the ribbon cable for the auxiliary board has a pin missing. I didn't think I lost a pin when I disconnected it but perhaps that's what happened. Does anyone else a pin missing on their auxiliary board ribbon connector? One last thing I tried was take the z80 chip and seat it directly on the mainboard. Same result except the screen gets wavy. Any thoughts or guidance would be appreciated!

yes, the ribbon cable is what carries the Z80 from the daughterboard to the main board. any broken pins on the ribbon cable gimmick will equate to being a broken CPU pin at the main board. out of absolute desperation at a location where I NEEDED to make the game work again I wound up jamming a cut off cap leg in there and it's seemingly still worked ever since lol

if you need a replacement this is where to get it: https://www.mikesarcade.com/cgi-bin/store.pl?sku=MPRIBBON

 

[djhurt1]

@mecha

Any idea why placing the Z80 directly on the mainboard produced similar result? I'm no expert but I read that placing the Z80 directly on the mainboard, where the ribbon cable would normally go, would allow the machine to boot?

 

[mecha]

@mecha

Any idea why placing the Z80 directly on the mainboard produced similar result? I'm no expert but I read that placing the Z80 directly on the mainboard, where the ribbon cable would normally go, would allow the machine to boot?

yes that would make it run as Pac-Man and is typically the first thing I would suggest doing in the condition yours is in but I didn't

have you done any work to the sockets on the main board? the conventional wisdom I share, from personal experience of course, is that the traces and solder pads on that old Midway hardware are very fine and even if you know what you're doing soldering you can disconnect a pad or something and the game won't be able to run then. if you have rom programming capability, seek out the Pac-Man test rom, it runs in the 6E socket. I have some non-working boards I keep wanting to run with my FPGA catbox. just not enough days in the week.

 

[djhurt1]

I've made some progress on this. After re-flowing the edge connector I was able to some logic back. I was still getting the garbled screen but now in diagnostic mode it said "Rom 1 bad". Looking this up that pointed to 6F. I already had another new chip coming from highscoresave.com. Once that arrived I now have a working "Pacman" lol. I've already ordered the replacement ribbon cable and that should be here by this weekend. Hopefully getting that replaced and hooking up the auxilary board again I'll have a functioning Ms pacman with original speed.