Weird color problem with a WG 25k7401

[xaryC]

Hi all,

I've been in the scene for quite a while and owned mk arcade machines for over 15 years. But now i run across a problem that I don't know what to do...

My monitor in my mk4 cab looked a bit washed out, colors just weren't right... I took the monitor out and did a cap kit but i couldn't see any improvements in the colors. Alltough the image was better in some way.
So i dug a little further into the monitor issues here on the forum and checked for cold joints, reflowed some pins and yesterday the colors lookef bright and very good. Tought I nailed it...

Today I wanted to put the cabinet in place and when i turned the cabinet the colors began to change. 

It't like the monitor is not desgauged.

I made a video of this to show you guys...


Is there anyone who can help me out please?

Thank you in advance!

[grantspain]

 turning a cab will cause that purity problem as you are changing the magnetic field, cabs should stay in one place and the degauss will only help after cab is switched off for about 20 mins
no idea why its so red though, most likely you bridged some solder across legs-you can prove gun by desoldering red gun pin on the crt socket

[behrmr]

Never rotate a game while it's turned on.  Now you need to rotate it to where the colors are correct.  Turn it off.  Then attempt to move it where it is you want to keep it.  That may or may not work.  If not, you'll need to degauss when it is put in its final spot.  There are many ways to do that if you don't have a coil if you search the internet.  Your monitor if working will do a light degauss every cold start so it may resolve itself on its own.

Do you have a video signal connected to the monitor?  Put a signal to it and then look at the colors.  And you probably need to color balance with the pots on the neck board plus all of the brightness and contrast settings on one of these.

[xaryC]

Thanks for the relplies!

Seems I got the notify off for this thread 

I installed 3 new transistors for the colors, and colors are much better now.

The cab is not yet in it's final place, but I picked up an old crt tv of witch I'm going to use the built in degaus coil to degaus it (does that sentence make sense? lol)

I still have another problem that I can't figure out. So I did a full recap, changed the transistors and changed all the pot trimmers (mainboard, neckboard and the mini control board).

When I turn te cab on, the picture is stretching horizontally and vertically for a few seconds to one minute. seems like it needs warming up.

Anyone know what or where to check here?

I'm sorry for my english... I'm dutch and not using english that much anymore


Thank you in advance!

[xaryC]

Made another video of my problem:

[grantspain]

as you alrady replaced the caps the issue is likely a bad solder joint
might be worth reading the b+ to see if its stable

what chassis is in there, judging from the frame its a wg k7000,k7400 or u5000

[xaryC]

as you alrady replaced the caps the issue is likely a bad solder joint
might be worth reading the b+ to see if its stable

what chassis is in there, judging from the frame its a wg k7000,k7400 or u5000

It's a P763 chassis k7401 monitor.

I will try reading the b+, just need to figure out where tough...

[xaryC]

So it's been a while since I reported my problem here... Last week I tought to look into the monitor again, stil has the same streching problem until it warms up...

Took out the chassis again to check some stuff. Nothing bad at first sight...

Hooked it up and tried it again, and now it didn't have the issue... B+ measures a steady 139V at test point 203 when game is running.
I will try again tomorrow when the monitor has cooled down and see what happens.

I guess the 139V is not bad?

Verstuurd vanaf mijn SM-A505FN met Tapatalk

[MKFan4Life]

I saw I think a WG U2000 or 5000 do this once and it was indeed a couple of cold solder joints. As temps changed in the game, the problem popped up. I could tap on the frame and the picture would freak out and try to change size and such.

I would take a picture of the bottom solder side of the chassis with a good digital camera and pull it up on a computer. Zoom in and slowly examine the joints, especially large solder joints. You're likely to find a few that look just fine with the naked eye, but when you zoom in on the computer, you will find a few with complete circular cracks around the pins. These areas will likely lose connection as the heat in the game slowly expands and pushes apart these connections.

Also, work your adjustment pots out and back since you might not have swiped the pots much in a long time. This will kind of clear off contamination and give a more stable resistance. Right now, certain adjustments might be going up and down in the resistance the chassis is seeing. It totally looks like someone is sitting there moving a pot back and forth.