Ms Pac Man Monitor Problems

[wxforecaster]

Thanks Ian. I had a bipolar joke, but will refrain So apparently the + marking on the underside of the board is incorrect at 301. The caps that were pulled at both locations do appear to be identical and of unmarked polarity.

Evan

 

[paul400]

Both of those caps are bipolar, 3.3uf capacitors, and must be replaced with the same. They're not included in the cap kits generally because they're not common failures. Don't replace them with a polarized electrolytic.

-Ian

they are included in bob's kit now, go ahead and replace them doesnt matter which way they go in.

 

[wxforecaster]

Well, I finally had a few minutes to finish the job off this morning. I was able to repair the bad plate through holes by jumping to a scraped off part of the adjacent board with some wire strands and old cap legs. Unfortunately, I don't have good news

At least I got the fan and the coindoor/CP lights both working after cleaning the dust bunnies, mouse droppings, etc...out of the bottom and reattaching a loose grounding strap.

The bad news is that my monitor has no picture. I checked all the continuity across all the caps that were replaced, and everything tested good before putting the chassis back in. I watched the board for any signs of problem after powering it up and there's no smoke, sparks, fire or otherwise. I *can* hear the high voltage. I just don't get a picture.

Evan

 

[RetroHacker]

Did you remember to plug the video cable back in?

Does the neck of the tube glow? It might be hard to see, but you should be able to make out a faint orange glow in the neck of the tube.

Also, did you replace the flyback while you were in there? If you replaced the flyback, you'll have to adjust the SCREEN and FOCUS controls. It could just be that the screen voltage is turned down so low you don't get anything on the screen.

Another quick thing to check is to turn the SCREEN control up - see if you can get a grey raster on the screen.

-Ian

 

[wxforecaster]

OK, now we're getting somewhere! The E1-E6 cable was not fully seated (<-- idiot mode off). That however didn't seem to make any difference.

However, when I turned up the SCREEN, I got a picture. Adjusting the focus slightly yielded Ms. Pac-Man, albeit scrolling wildly to the left. I'm sure the 303/501 mod had something to do with this.

Obiviously I found the Screen and Focus adjustments, and I see R,G and one other adjustment on the neck board. There appear to be pots on the front of the chassis, but they don't have knobs and so I'm not sure how to adjust them without the risk of breaking them (is one of these the H hold?)

I hope all these noob questions will help out others and you have no idea how much I appreciate your guys' help and patience!

BTW, I did not replace the flyback. When I got the dirt cleaned off it and everything else, there were no signs of wear.

I would like to test the B+ voltage when I'm done, but I'm not sure where the test point is (a graphical diagram would be most helpful!)

Evan

 

[RetroHacker]

The "pots" flat on a G07 chassis have no knobs, you just have to turn them carefully with a flat bladed screwdriver.

There should be a second, smaller cable that plugs into the G07 chassis from the game - a little three pin one. It's the sync signal. Is that connected correctly, and not off a pin?

The test point for the B+ on the G07 is on that large ceramic resistor on the side of the chassis. Test at the end closest to the picture tube. The black lead goes to the chassis ground. You want 120v.

Also, scrolling to the left (assuming you're looking at the screen as you would play Ms. Pac), would be vertical hold. The hold controls correspond to the tube as if it were oriented like a television.

-Ian

 

[Peale]

This thread needs to be stickied:

http://forums.arcade-museum.com/showthread.php?t=196257&highlight=Common+G07

If your G07 flyback is original, REPLACE IT WHEN YOU CAP IT.

 

[wxforecaster]

SOOOOOOOOOOOOOOOO close now!!!

The B+ voltage was down at 103.7V. Rectified that to 120V and most of the scrolling went away (the tiniest of V hold adjustments took care of the rest). I was able to use the V-lin, V-height to get a nice filled/centered picture and used the H-freq to clear up the top/bottom being slightly off screen. I was a bit unnerved that the H-freq pot sparked when I put my screw driver in (none of the other pots did).

Anywho, what I'm currently left with is an odd issue. With the cocktail hinged open, the monitor colors are spot on and drop-dead gorgeous and the image is crisp. There is some curl along the extreme right side of the maze. However, as I close the cocktail, the colors gradually change are completely messed up (Ms. Pacman looks like she ate some bad mexican). I can reproduce this by opening/closing the hinge. See below.

I've read about degauss issues, but I'm uncertain as to why moving the monitor would do this unless it's the 90 degree change in the magnetic field plane. So, is this a degauss coil fix or something greater? Also, which adjustment would clear up the slight curl noted in the far right portion of the maze?

http://www.interwarn.com/pictures/mspacopen.jpg
http://www.interwarn.com/pictures/mspacclosed.jpg

Evan

 

[smalltownguy2]

Try rotating your cocktail cabinet 90 degrees.

Try moving it 4 feet in any direction.

I'm not kidding - I've got a buddy who couldn't for the life of him figure out why he couldn't degauss his monitor in the cab's current position. He moved the cab 6 feet to the left and his issue disappeared completely.

 

[RetroHacker]

The Earth's magnetic field affects the monitor. You powered it on in the open position, so the internal degauss circuit in the monitor degaussed the monitor in that position. Move it, and you change it's relation to the Earth's magnetic field, and the purity gets messed up.

Shut the lid of the cocktail. Turn off the game. Let it cool down for a half hour to an hour, and turn it on again. Once the degauss thermistor cools down, the internal degauss circuit will operate at poweron. That should be all you need - although occasionally it needs to be done twice.

You can see this yourself - turn your computer monitor onto it's side, and watch the colors get messed up. Use the front panel controls to degauss it (modern computer monitors have the option of manual degauss, old arcade monitors and televisions do not). Watch as the degaussing clears up the colors. Now, rotate it back upright. The colors are out of whack again! For bonus points, do this to someone else's monitor at work, and leave it screwed up...

(obviously this doesn't affect LCD's)

-Ian

 

[wxforecaster]

Success!!!

Can I get a "HELL YEH!!!"

I have to say, this has been one of the most enlightening threads ever. You guys have made purchasing a non-working machine one of the most enjoyable decisions I ever made. I only wish that I had retained 10% from that "PHYS 202 Electricity and Magnetism" course I aced back in college

I would love to take your advise Ian, but alas we are all LCDs at work now

Curl fixed with a minor adjustment to the V-hold. Colors are crisp and sharp after leaving the cocktail closed and powered off for 30 minutes.

I will hereby deem the cap kit a success and this thread closed.

I cannot believe I acquired this for a mere $100 two weeks ago, and for a mere $14, some patience and a few hours work, have a perfectly working game!

On behalf of my wife and kids, thanks to "THE" Bob Roberts, Ian, Paul, Peale and others for being such an incredible asset to the community. A little knowledge goes a LONG way.

All the best,
Evan

 

[smalltownguy2]

Hell yeah!

Welcome to the madness. Soon you'll be ripping up flooring in one of the rooms of your house for an in-house arcade.

 

[wxforecaster]

Already did that I'm mainly a pinball guy and have 7 of em down in the basement. I had amassed a pile of web links, articles, books, etc... on building a MAME machine once my son gets a bit older. However, when I saw a Ms Pac CT for $100 on CL that aesthetically looked great, I wasn't going to pass that up under any circumstance, and sped over to the guy's house within 15 minutes of it being posted.

This cocktail is going into the living room where it belongs

Evan

 

[smalltownguy2]

This cocktail is going into the living room where it belongs

.