Pacman vertical yellow/green lines

kalevan

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For as long as I've had this Pacman machine, the picture has been plagued with a yellowy-green haze and vertical bars (they're yellowy-green, too). I finally got brave enough to install a cap kit from Bob, hoping it would solve the picture problem. Got the monitor back in... and the same lines are present; no improvement at all. Big let-down- my first cap kit, and foiled!

It's a WG 4600 series monitor, and below are some post-cap kit pics. I'm noticing that it appears slightly out of focus now, too... like the images are ghosting (har har) right below themselves.

I suppose my questions would be: Does this indicate a board issue? And if so, does anyone have any suggestions as to what I ought to try next? Within the last few weeks, I've cleaned the power supply, replaced the fuses and fuse blocks, and thrown a new plug on the cord so that I can once again have a grounding pin. I'd like to really get this looking sharp, but need a push in the right direction.

I see a similar issue at arcade game over that says, but the pic is so small I can't say whether it's a match, for sure:
128 Bars on screen. Hazy shade of Yellow or Red over entire screen.

2C short p7 to p4 yellow.

2D short p7 to p4 red.

I don't know what to do with this info, though. I don't have 128 bars, either... mine are weird: they are wide on the left side of the screen, but get closer and closer to each other on the right

Here's the pics.
 

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How does the monitor look if you hook another board up to it? If you have another game and can move them close enough to get the video cable to reach the 4600 in the Pac, check it out.

When I see lines like that, I usually have my brightness turned up too high on the monitor. The green/yellow could be because you're having to over compensate for a missing color as well. You could be losing that color because of cold solder joints under the daughter card your video cable plugs into (just fixed one here that was doing that). Reflow those pins, as well as every other connection pin on the chassis just to be sure.

Could need a cap kit (never hurts), and also check your brightness on the flyback and chassis. Make sure they're not up too much, if they're close to being maxed out, then you're going to want to do that cap kit to hopefully fix that.

As far as the blurring goes (not being sharp), that's an adjustment on the flyback as well. There are two knobs, one does brightness, the other does focus.
 
Seeing you've already done a capkit - eh herm ;)

Brightness - turn it down. Since you haven;t provided the actual monitor model number all I can say is use the setting on the flyback to accomplish this.
I don;t know the history of this machine but all too many times people get in there and start turning the color pots and jack it all up. Once you get rid of the lines then start using the color pots on the neck board and attempt to turn down the green drive pot.
Reflow the solder on the neck board
Tube might need to be rejueved
You could also have a gun going bad on the tube

A lot of things but try these first.
 
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Seeing you've already done a capkit - eh herm ;)

Brightness - turn it down. Since you haven;t provided the actual monitor model number all I can say is use the setting on the flyback to accomplish this.
I don;t know the history of this machine but all too many times people get in there and start turning the color pots and jack it all up. Once you get rid of the lines then start using the color pots on the neck board and attempt to turn down the green drive pot.
Reflow the solder on the neck board
Tube might need to be rejueved
You could also have a gun going bad on the tube

A lot of things but try these first.

Yeah, sorry about that... managed to miss the part about "post cap-kit".
 
Either my pac or I am cursed... maybe both, in fact. I pulled the board and decided to reseat a few chips to see if it'd have any effect. Plugged it back in and now I not only have the yellow haze and lines of doom, but I'm getting nothing but garbage on the screen.

It had an effect, all right. Frick.

As far as the model number, it's a 4606. Would any other number be helpful? Tube says it's wg889921. I'll see if I can plug another game into it when I can. I've spent the entire day on this thing so I'm going to have to put in some serious family time tomorrow.

Any techs in the Inland Empire, CA? I'm beginning to think I could benefit from a hand.
 
I would say that is likely a monitor adjustment issue but could also be a problem on the monitor like bad color pot.
Have you adjusted the pots on the neckboard yet?
 
The pots on the neckboard... the red, green, and blue, I've adjusted, yes. There are two on the opposite side of the board that seem to have no affect at all... R drive and B drive? Screen makes it incredibly bright or incredibly dull, but the lines are visible regardless of the "screen" setting.

Haven't found the focus yet, but I'm sure it'll turn up next time I poke around in the cab.
 
Okay, had to pull out my Crazy Kong and have a look at the boards and flyback. I spoke too soon, there is no brightness on the flyback on 4600, just focus.

Check the "black level" pot on the solder side of your RGB card (the card your video cable plugs into). I over look that little guy all the time because he's not grouped with anything else... or even in a reasonable location for that matter.
 
Which is why you install it on the opposite side of the card when you replace it. Makes it easy to get at to adjust.

Fortunately, I haven't had a need to replace one yet. I have been thinking about just getting a new pot and epoxy'ng that thing to the front edge of the card just to make it easy to get to. As for adjustments, I've been lucky as to what cabinets I have 4600's in, Crazy Kong is a cabaret, so it's east to reach around and see, the other 4600 is in Robotron, and God bless whoever thought of putting that little mirror above the monitor tray in those cabinets... he's my hero.
 
Yes, I did see that pot in the kit, and I did replace it, but I did not put it on the opposite side of the board; it was my first cap kit and I couldn't work up the guts to be fancy - I was sure I'd screw it up. :irony!:

Thank you for taking the time to check your 4600s, Scucci, and thanks to all who are trying to help. I always appreciate this board's general willingness to help people out.
 
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I think Bob mentions putting the pot on the opposite side in the instruction page.
....you didnt read the instructions did you? :)
 
haha, I've been guilty of that plenty of times, but this time I just wasn't brave enough to do as he suggested. With caps, I hear all the time not to put them on backwards, polarity, etc., etc. and here it said to place this pot on the opposite side of the board? I decided just to keep it as it was. Like I said, I had no desire to be fancy with my first cap kit. Now that I've squeezed my hand in between the two boards and adjusted it a few times, I see that it would have been wise just to listen to Bob and do it his way. I find I tend toward having to learn things like this the hard way.

Anyhow, adjusting said pot made no difference with the lines. Back to the drawing board I go.
 
I have exactly the same problem with my Pac-man board: green diagonal lines across the screen. I have tested my monitor (a recently recapped 19K4606) with another board and it looks great, so I'm thinking it's a problem with the Pac-man PCB. I've adjusted every pot on the monitor just to be sure, but nothing I do gets rid of the green lines/haze.

OP, are you able to test your board with a known working monitor?
 

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I have exactly the same problem with my Pac-man board: green diagonal lines across the screen. I have tested my monitor (a recently recapped 19K4606) with another board and it looks great, so I'm thinking it's a problem with the Pac-man PCB. I've adjusted every pot on the monitor just to be sure, but nothing I do gets rid of the green lines/haze.

OP, are you able to test your board with a known working monitor?

Amazingly enough... I found a page that MIGHT just have the solution.

http://http://lawnmowerman.rotheblog.com/#playsbut

Especially the part that say "Plays, Green running dashed lines on the screen otherwise okay. Replace 74LS75 @ 3D."


Worth a shot.
 
Amazingly enough... I found a page that MIGHT just have the solution.

http://http://lawnmowerman.rotheblog.com/#playsbut

Especially the part that say "Plays, Green running dashed lines on the screen otherwise okay. Replace 74LS75 @ 3D."

Worth a shot.

Thanks Scucci, that could be it. I tried disconnecting the Green signal going to the monitor from the PCB and it made no different to the image, which tells me that the Green output of the PCB is not doing anything. If I swap the Blue and Green inputs, the monitor turns blue with blue diagonal lines, so this must be how the monitor looks if any of the colour inputs are floating. (or grounded?) If I connect both Green and Blue monitor inputs to the Blue PCB output, the haze/diagonal lines go away and the image looks clean. (but the game colours are wrong of course)

kalevan, I suggest you try the same steps on yours as it might help to find out if the problem is with your PCB or your monitor.

I'll poke around a bit more and make sure it's not just a resistor or broken trace. If I need to replace 74LS75 @ 3D or the following 74LS157, where is the best place to order these old integrated circuits?
 
Problem solved!! :D

I did a continuity check between the Green signal on the wiring harness and the resistors R13-R15 near 7F on the board... no connection! I narrowed it down the actual edge connector trace itself. That particular one is really worn down, so there was no electrical connection between the PCB and the harness. I just plugged my harness in all the way, but backed it off just slightly to move the contacts off the worn spot, powered everything up and it looks great.

OP, make sure your "Green" signal is actually connected all the way from the R13-R15 resistors to the input of your monitor!
 
Ooo... just when I'd about given up hope on this darned thing.

I'll give it a shot! Thanks for the info!

Edit: Ok, good Christ. I've been screwing around with this blasted thing for a week and a half. It's been DEAD as a doornail. I cannot believe that it is working now that I have simply backed off with the harness like you mentioned. Still has the green lines and still looks terrible, but it WORKS. Bless you, delroy666!

I'll check on that green signal (*pretends unconvincingly to know how to do that but determinedly resolves to find out quickly*), but I should probably ask your question above again, just in case: If I need to replace 74LS75 @ 3D or the following 74LS157, where is the best place to order these old integrated circuits?
 
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