Monitor turns red intermittently on MK II

cadegallery

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Hi all, pretty new to arcade restoration so go easy on this noob. So my issue is, I have a MK II, was originally a Simpsons four player. The monitor will go red at random times, like, just a shade of red, where you can still play the game, but everything will be awash in red. We thump on the side of the cabinet to get it back to normal, which usually works, but it always goes back to red eventually. Any ideas on what I could do to fix this? Thanks KLOV!
 
Could be alot of things. Bad solder joint somewhere on the monitor chassis, bad or dirty red gain or cutoff pot, back connection at the backboard. bad red gun in the tube(shorting), krappy connection at the jamma connector, etc.


Power it up and gently wiggle the jamma connector, if your red goes wacky, you found your issue. If not, wiggle the rest of the harness. If you cant find an issue with the harness, its time to start poking around the monitor.


Have any idea what brand and model monitor is in there? It wont be on the tube, thats just the tube maker info. If you dont know, just post some pics and we can help id it.
 
I would lean towards it being either a

A. intermittent short in the tube
B. Dirty pot

Typically bad wiring or crappy connections will make colors dissapear, but it doesn't really have a way to make a color lock on full blast.

I've seen before too depending on the model, if the metal tab of the red transistor accidentally touches one of the tabs of one of the other transistors, it'll make colors go crazy.
 
Could be alot of things. Bad solder joint somewhere on the monitor chassis, bad or dirty red gain or cutoff pot, back connection at the backboard. bad red gun in the tube(shorting), krappy connection at the jamma connector, etc.


Power it up and gently wiggle the jamma connector, if your red goes wacky, you found your issue. If not, wiggle the rest of the harness. If you cant find an issue with the harness, its time to start poking around the monitor.


Have any idea what brand and model monitor is in there? It wont be on the tube, thats just the tube maker info. If you dont know, just post some pics and we can help id it.

I'm gonna take a shot and say that if the game was a dedicated Simpsons at one point, that the monitor is a wells k7000 series.

Probably cold solder joints at the r g b sync header pins, especially if when you "fonzy" the game, the color goes in and out. You should pull the monitor chassis (board) off of the tube and frame, and re-flow those and any other questionable solder joints on the neck board and monitor board. You should probably also cap this monitor since if it is original simpsons and hasn't been touched, it has 20 year old components on it.

Cap kits can be had from bob Roberts (www.therealbobroberts.net), or twistedquarter on eBay, for around $10.

There is a sticky thread at the top of the monitor repair section that explains soup to nuts how to repair the k7000 monitor (cadillacman here has made many contributions to the thread), and it is a treasure trove of information.

Don't be intimidated by monitors. I used to be, until I fried my brain by accidentally touching my tongue to the anode coming off the flyback. Now, I don't even think twice... Mainly because I can't.

Just kidding. Grab a soldering iron, and have fun. Welcome!

Mike
 
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