Ms PacMan dead G07

[mclovin]

Hello all, I just picked up a dead ms PacMan game from kijiji. I can hear audio when powered up, but there is no video. Just black screen and there does not appear to be any neckglow. Where should I start troubleshooting with this?

Thanks again everyone! I'm addicted to picking up arcade games that I need to try and fix.

[baritonomarchetto]

Take out the pcb then turn your monitor on: Do you hear any "sound" coming from it? A "tik-tik-tik" like noise or something like that?
Being very likely that the cab is juiced with a linear PSU, it's probably better to disconnect it and leave the pcb where it is (linear PSU dont like to run with no load applied)

[mclovin]

OK unplugged PCB and powered unit up, no ticking or noise from monitor, slight humming I think is coming from the 2 big power coils?

I checked and I am getting 120 volt power to the two power wire plug feeding the monitor chassis.

[baritonomarchetto]

 When you turn it on, do you hear the high voltage high freq noise (and the electrostatic charge on the screen glass) for a second, then it shuts down or it shows no signs of life at all?

[mclovin]

Ok when it was unplugged for a while when I first powered it up I heard a quick split second hum from the monitor and that's it. Then I could not get it to do it again. No static sounds or anything else.

[baritonomarchetto]

Ok, check the chassis fuse/fuses then

[mclovin]

Fuses are good, replaced the caps, found a couple bad ones, one at c905 was coroded and leaking so bad one leg wasn't even connected. Unfortunately that didn't make a difference. Put it back together and same thing. Noting.

[mclovin]

Correction Fuses were good. When I put the chassis back I blew fuse F901. Looks like the 120 volt supply plug can plug either way. Both wires are black going back to the chassis and not labled, how do I tell what one goes to hot and what goes to common?

[baritonomarchetto]

It's alternate current, so no problem connecting the poles reversed.
Probably the fuse was on it's last leg: replace it with a slow blow fuse with the same current (ampere) rating, turn on and check if blows. If yes, you have very likely an issue in your DC (not AC!) power supply circuit (the diode bridge or filter cap or something in the circuit); if it doesnt blow check the solders of the fuse holder (and all the other solders, at least of the power supply circuit, just in case).

[mclovin]

Thanks for your help! I'll try that tomorrow. One other thing I have found is my HOT is shorted out. So would this make the monitor have this dead issue or is it just another problem? The flyback is not cracked or anything. Where do I buy the HOT?

[baritonomarchetto]

You could have a shorted flyback, but how did you test it? The flyback is essentially a collection of coils, so it's normal to measure shorts between most of the pins

[mclovin]

I found some info online on how to measure the horizontal output transistor @ H01. I have a ECG89, and it measures short between two pins, and in diode mode it should measure around .5 volts, it also measures short from the outside of the unit itself to the chassis case/ground. Again I have no real idea what I am doing, I just found this info on the net. Is this correct?  As the flyback goes, I am not sure if it is bad or not, but there are no visible cracks.

[baritonomarchetto]

Sorry, i associated the hot to the flyback (i must stop working and replying at the phone at the same time )

Not volts but ohms: you whould perform a resistance read

[mclovin]

Yes, Sorry my bad.

[mclovin]

Now I powered it up again with a replaced F901, now it blew f902 when powered up. ??

[grantspain]

g07 is the type of monitor you should do a shotgun job on,new flyback/HOT/caps/fuse and width coil

[mclovin]

 When I remove the HOT it no longer blows the fuse. I will order the deluxe rebuild kit from Bob Roberts and hope for the best. I'll post back the results. I'm just worried that something else is shorted and hope it doesn't blow any if the new replacement parts.

[mclovin]

Just waiting on the rebuild kit to come. In the meantime I got ahold of another chassis that has its own issues I get it fired up and picture looks ok except it is way high on the screen, say 10% is cut off the top. Tried all pots for adjustments and nothing makes it any better. Checked the caps, all fine. Has anyone seen this before? Now I have two chassis to try and make one good. So then I swapped the HOT from the one with the screen issues and put it in the first one that was blowing fuses. Now it starts up doesn't blow fuses anymore and has neckglow now, but just black screen. Checked DC volts at R1 and it seems ok. I'm getting closer but still looking for some experienced gurus to guide me.

Thanks again!

[baritonomarchetto]

If swapping the flyback it works, well you have likely found your bad unit. If you have neck glow, rise your G2 by acting on the flyback screen potentiometer: you should see your raster.
As per the out-of-screen image, replacing the caps should fix (bad caps in the ps circuit and vertical deflection circuit could cause the issue).

[mclovin]

I got it working now! The final problem was that the flyback remote control pots were different with the 2 chassis(both g07 but different revisions), one only had a single focus pot, the other had a focus and screen pot. Swapped them around and it fired right up. 

[mclovin]

Just in case others that are having problems swapping chassis from another machine. There is some interesting reading on Bob Roberts about this horizontal issue where one chassis will work perfectly with one game and it will be off the screen on another where it is was way too far out of adjustment for the horizontal width coil. Replacing the polypropylene capacitor with a different value should fix this problem.

Common Width Cap Positions
Wells-Gardner K4600 Series - C615
Wells-Gardner K4900 Series - C365
Wells-Gardner K7000 Series - C38
Electrohome G07 - C515