No power to Pacman; could use some advice.

kalevan

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My latest trouble with Pacman is easy to describe: nothing happens when it's plugged in.

Skip this paragrah if you want to get right to the "good-parts." Some history here: I have recently had some trouble with the machine displaying garbage. I found that a leg on the brown socket connecting the board to the z80 had broken off. I decided that I would take this opportunity to do some fall cleaning, so I ordered a few sockets, a new fuse block, and set of fuses. After resocketing the board and reconnecting the z80 daughterboard, I disconnected the power supply, cleaned everything, replaced the 4x fuse block and fuses, reconnected everything, and attempted to power up this afternoon to find my Pacman flatlining completely; nothing. No lights, no power; apparently I messed something up.

I've spent the day afternoon searching the web and reading a number of threads here and there which describe problems similar to mine, but to be honest, I don't understand how to check for where my power is failing. I have a multimeter, but it remains mostly a mystery to me. I can check for continuity, but that's about all I can do at this point. I know the fuses are still good, but I need a crash curse in checking Pacman's vitals if I'm going to be able to see where I went wrong and have any hope of fixing it.

I have found schematics, but again, truth be told, I don't know how to read them and put them to use. I've read a few threads here that say what to check, but I'm boggled as to how to check it, so I'm going to throw myself at the board's mercy and ask for some very basic troubleshooting for dummies here. Would anyone mind telling me where to begin digging for answers and how to begin? I've been to Bob's site and Lawnmowerman's site, but what I could really use is some basic tutoring in how my multimeter can help me find the source of my Pac's woes. I've already taken the switches into account; my backdoor kill-switch and the top-mounted power switch have never worked - they seem to be bypassed. Turning it on/off has always been a matter of plugging it in/pulling it out.

I see this in the troubleshooting guide: Check the transformer's primary connections, and look for 117VAC. It also says I should check the secondaries and correlate the readings with the legend on the side of the transformers. I'd love to, but how? I know what the transformers are, but I don't know what primary/secondary connections are.

Thanks in advance for any help you can give. I'm going to keep searching tomorrow after work, but I'd appreciate any helpful advice that can be offered in the meantime. I understand that this question probably seems very basic and easy to many here, and am a bit embarrassed about being as clueless as I am!
 
Read the schematics for the board... look at the edge connector section to see what should be coming off the wiring harness.

Also, check those pesky interlocks on the cabinet.

RJ
 
replace the fuse holders. they get weak over time and they dont grip the fuse tight enough to allow proper game operation.
 
Did that with the 4x fuse block, but not with the 2x. Might run down to the Shack and get a replacement for the 2x tomorrow after work. In the meantime, I'm trying to get a good idea of how to use a multimeter to check where I'm losing power.

Thank you both for your replies. Any other advice/suggestions are more than welcome.
 
If your not getting power to anything (marquee light, monitor, pcb), check the 2X fuse holder, on/off switch and interlocks. Using a volt meter, verify power starting at the power cord and work your way in.
 

set the multimeter to 200 AC voltage.
put the black lead on the black input wire from the wall.
put the red lead on the white input from the wall.

you should get 115-120 Volts ish

now, set the multimeter to DC 20 volts
attach the black lead to ground, either on the frame of the transformer or on the metal can of the small silver box (line filter) the one with power wires in/out.

probe where the red wires are going into black connector on the gameboard Printed Circuit Board. you should have +4.9 - 5.2 Volts ish.
if you dont have +5 volts there, then your power supply is probably the problem.
 
now, set the multimeter to DC 20 volts
attach the black lead to ground, either on the frame of the transformer or on the metal can of the small silver box (line filter) the one with power wires in/out.

probe where the red wires are going into black connector on the gameboard Printed Circuit Board. you should have +4.9 - 5.2 Volts ish.
if you dont have +5 volts there, then your power supply is probably the problem.

SG, this is not going to be correct. Pacman uses 7vac to the board, and the board makes it into +5vdc.

That being said, the reading that you will be looking for is 7vac going to the board.
 
my bad. JAMMA brain.

measuring before and after the connector will tell you the condition of the pin inside the connector gripping the PCB. if theres a voltage drop then the pin needs to be replaced. check the condition of the pads where the pin grips onto if it seems you arent getting the proper voltage on the PCB.

some, just replace the connector with a new one to eliminate potential problems. take it off and look inside. is the spacing the same pretty much? if one looks more open than the others, the pin is weak. is the pin oxidized? that could add resistance to the electron flow and keep the game from operating. wire going into the back of the pin look ok?

you got 3 prongs on the plug?
 
Thank you very much, all. I've spent so much time trying to figure this out over the past two days that I'd better take the night off and put in some family time, but I'll try out your suggestions tomorrow evening after work.

Thanks again; I was getting discouraged, but now I've got a good idea of where to begin.

Edit: 2 prongs. Better get a new end for the cord, eh?
 
Re:

I had a similar problem with my Ms. Pacman when I first got it, the first thing I checked was the round power plug which can be taken apart, and sure enough, one of the wires came loose from inside the plug. Hooked it back up and wallah..., but now I have monitor problems but at least I know it works now. It might not be it, but it's worth a check.
 
Pac lives once again! Thanks to all who offered up advice; I really appreciate your efforts. As it turns out, it was the 2x fuse block. With a quick run to Radio Shack, I was able to replace the fuse block, which had nice 1/4" connectors for quick-disconnects, saving me the trouble of soldering.

I did solder the new 4x fuse block, which I ordered from Bob Roberts (bless him, he's my hero), and in the process burned a finger and remembered that soldering isn't as easy as it looks. Sigh...

Anyhow, thanks again. Here's some before and after pics for your viewing pleasure. I've got a few things to finish yet, as you can see.

Next step, cap kit... after LOTS of soldering practice.
 

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I had a similar problem with my Ms. Pacman when I first got it, the first thing I checked was the round power plug which can be taken apart, and sure enough, one of the wires came loose from inside the plug. Hooked it back up and wallah..., but now I have monitor problems but at least I know it works now. It might not be it, but it's worth a check.

wallah??????
 
wallah??????

Voila!

People spell it like it sounds and not like the French word it is.

There's supposed to be an accent over the a, but if you put it in the forum pukes and won't process the post.
 
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