WG4901 - Color Issues

[tristan]

I have this WG4901 monitor, and all I get is a blue screen with white/purple horizontal lines scrolling across it:

Image removed


I just installed a cap kit, and it seemed to help to the extent that the blue used to just cover the bottom 2/3rds of the screen. There is virtually no indication of what is going on in the game, except the horizontal lines flicker when the flashing at the beginning of the attract mode would be playing. The characters and vertical lines you see are burn in.

I'm not sure how to proceed from here. Should I try adjusting the colors on the neckboard, or is this something someone's seen before?

 I will say that the retainer(?) that holds the pins that come out of the back of the tube is broken, but it doesn't seem to have affected anything inside the tube, and all the pins still plug in:

Image Removed

Thanks

[Ken Layton]

It is common after doing a capkit to need to readjust some or all the controls (or maybe none at all) on a monitor. Looks almost like the horizontal hold is slightly out of adjustment on yours.

[tristan]

I picked up some monitor alignment tools (so I don't go frying myself), and I was going to attempt to adjust this tonight. Are there any other adjustments anyone would recommend trying?

[tristan]

I've been messing with the adjustments for about 45 minutes, and I've been able to recognize a picture. I can't seem to get it to stop scrolling diagnally across the screen:



I can make out about 3 screens at a time and they all scroll diagnally from the bottom right to the top left. They look better in person than in the picture.

Is there some way to go about adjusting these things other than blind luck? Also, I seem to have lost about an inch on the top and bottom of the picture, any advice on that?

Thanks

[Ken Layton]

This model is a standard resolution monitor. You aren't trying to feed it a medium resolution signal are you?

Are you feeding the sync signals to the correct pins on the input connector?

[tristan]

It's plugged into a Double Dragon PCB, and I haven't changed (or checked) the wiring on the connector. The whole thing was given to me after several years in storage.

[tristan]

OK. I got inside and got a good look at the connections to the monitor.

The red, green, and blue go to the red, green and blue pins.
The ground next to these on the monitor is not wired.
The Video Sync on the JAMMA goes to the -V sync
There is a jumper cable from the -V sync to the -H sync on the monitor
The ground on the monitor runs to a common ground on the JAMMA harness instead of the video ground.

Does this seem right? Will the common ground work instead of the video ground? Could this be a bad connection with the jumper wire?

[tristan]

The purple one at the top goes from the -V sync to the -H sync on the connector.

Anyone know where to get new 6 and 3 pin connectors for this cable?

[tristan]

I'm still not sure what that connector is, but it looks like a molex KK style (size?) on the MB. Anyone?

[tristan]

Well, I found Randy Fromm's troubleshooting flowchart and I came to the box that said
"You have a sync problem. Make sure the composite negative sync from the game PCB is connected to pin 3" It then goes on to say it is a common mistake for it to be jumpered as it is. I connected only the 3rd pin, and now all I get is a purple screen with no sign of the game whatsoever. Adjustments seemed to do no good. Color adjustments do change the color of the screen.

I suppose it's on to test/replace transitor Q301 and IC301. Still looking for a souce for that connector...

[Ken Layton]

mouser.com

# 538-09-50-7031 3 pin connector housing (17 cents each)

# 538-09-50-7061 6 pin connector housing (34 cents each)

# 538-08-50-0108 connector crimp terminals (6 cents each)

# 538-63811-2200 crimp tool

[tristan]

Thanks Ken.

I was thinking about just replacing the whole chassis with a replacement:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=6191852928&sspagename=ADME:B:AAQ:US:1


Is there a possibility here that the tube is the issue? Is this worth the price ($72 shipped), or does anyone know where to get a good replacement for cheap?

[tristan]

I replaced the transitor at Q301 with no success. I then proceeded to look over the mainboard comparing it to a picture of a good one. I noticed that there are two pins sticking out of the mainboard where the vertical raster pot should be. I assume this could be the real issue here. I looks like it is on some sort of riser board with some components on it.

Anyone know where to get this board/pot assembly? The manual is not helping me today.

[Ken Layton]

There are two versions of the 4900 series: early and late.

The early only had the usual horizontal and vertical raster positioning tabs where you move the jumper wire to whichever of the three tabs gives best positioning.

The later version had added a small vertically mounted circuit board with a transistor and a pot on it for much better vertical positioning. This chassis uses a different yoke than the early one. With this chassis there were several changes done to the vertical deflection circuit that neccessitated changing to a different yoke.

[tristan]

Looks like it is the older one.

I suppose a newer chassis wouldn't work then. Anyone know where to get a cheap replacement chassis?

[SirPeale]

The ground next to these on the monitor is not wired.
The ground on the monitor runs to a common ground on the JAMMA harness instead of the video ground.

Does this seem right? Will the common ground work instead of the video ground? Could this be a bad connection with the jumper wire?

I'd wire it properly, just to be sure.

[tristan]

Yeah, I got in some new connectors today, and I'll probably try that first. I'm still not 100% sure that pin 3 is a composite input, as I only seem to get any sign of a signal when 2 and 3 are jumped.

[tristan]

Well, I've located a manual for the older style 4900, and it does say to use the -H for composite. Also, there are two pins that should be jumped when making adjustments. I'll be trying one last time tonight to bring this baby back from the dead.

[tristan]

Well, I'm no longer sure this monitor is bad.

I rewired the cable, and moved the ground over to the monitor ground, to no avail. I then pulled a K7698 monitor out of a working cabinet (uses the same wiring), and I get no picture at all on that monitor. I'm starting to wonder if the ISO transformer (original Defender) isn't outputting the proper voltage, or the JAMMA harness is bad.

I'll probably just rewire the entire cabinet at this point, as all I need is a new pre-wired JAMMA harness. I have a known good PS, ISO transformer, and power filter that I will use.

Thanks everyone for your help, when I figure this out, I'll let you know.

[tristan]

Well, it's been a while, but I rewired the entire cabinet, and the K7698 works perfectly in it now.

I want to try the original monitor again, but after I replaced the transitor at Q301, I started getting pincushioning at two points on each side. This was a "replacement part" so I assumed it wasn't quite right. I purchased a part from Bob Roberts, but the part appears to be slightly different:

Original:
C1815
GR 2C

New Part:
C1815
Y  0A

My question is, should I try the new part, or should I just put the original back in? Any Idea what the letters on the bottom mean?

[grantspain]

just read through your original post on this,if the machine had been sat around for a long time the tube will take along time to recover(if ever),your photo seemed to me to imply that your focus pot on the lopti needed tweeking and you had some sort of sinc issue-that transistor number seems ok its that first number thats important,im pretty sure those bottom numbers are production and maker details.what your fault now and can you post a photo.

[tristan]

Well, I put in the new transistor and the pincushions went away. I now get a complete picture for the first time. Now the game takes up a good chunk of the screen near the lower left side. The entire screen appears to be washed out with blue, but other colors are present. I'm hoping some adjustments will help now, and I've attached a photo if anyone has any suggestions for adjustments:

[grantspain]

looks good ,to centralise the picture use the horizontal position pot and the verticle position pot-you will find them either on the chassis at the back or on an control card which is connected to a cable coming from the chassis or on the chassis itself-the blue is the blue cut off pot needing adjustment,you should find this on the neck card-this is where all your color controls(background and foreground should be found depending on chassis type).
if your color is still bad after adjustment then it could be down to a dry joint on the neck card or a faulty transistor,if you took a photo of your chassis from the back i may be able to help more,good luck

[Ken Layton]

Try turning down the "Black Level Control" (just a fancy name for brightness) on the monitor main board. Also try turning down the "Screen" control on the flyback a tad bit.

[tristan]

As you can all tell, I'm very slow (and usually pretty lazy). I've fiddled with the color controls and the black level and screen controls, and I have come to the point where I think there is still an issue left.

The colors seem to be bleeding into each other near the top and bottom of the screen (left and right in the Pacman game), and I cannot seem to get red to look correct at the center, no matter the adjustments. The red and yellow seem to blend, as do the white and blue. The red drive pot on the neckboard is bent up, but the joints look OK. I currently have this in a Pac-Man game, and it works OK, but I can't tell the difference between some of the ghosts, especially in the center of the screen (no red)

Is it possible that the tube is shot, or does this sound like something on the PCB that could possibly be fixed? I'm moving into a house next month (out of my smallish loft), so I'll have a workshop again!!! Next up, the G07 out of the PacMan...

I also just want to thank everyone that's helped me with this so far.

[Kevin Mullins]

"Bleeding" could simply be the FOCUS on the flyback.
(hopefully not convergence)

Does the monitor seem to degauss properly?

[Ken Layton]

Bleeding could be that the neckboard pots are turned up too high.

[tristan]

When I say bleeding, I mean that the colors basically get replaced, not that the color is poking out around the edges or anything (if that is really any more clear). I couldn't really get a good picture to explain what I mean, I'll try to get a picture of the issue up soon.