WG K7900 issue.

bongoben

New member
Joined
Aug 7, 2008
Messages
2,250
Reaction score
7
Location
Wisconsin
Was playing a couple rounds of Cisco Heat tonight and everything was working fine when completely out of the blue (no pun intended) the screen turned blue. The game was on for about 2 hours lastnight and worked fine. Tonight I was about 10 minutes in when this happened. It's a WG 19K7901 chassis and is dustier than any chassis I've come across yet. I haven't taken the time to pull it but I assume a cap kit is in order. The screen looked perfect before then it was just mid race it jumped to what you see in the pics below. It is still playable like this just highly annoying. It sucks because the picture was perfect... no burn, no color issues... just perfect. Then it did this.

I'm assuming I have a short somewhere on the board since it just flipped from being perfect to this but I'm really not sure.

Any ideas?
 

Attachments

  • IMG00177.jpg
    IMG00177.jpg
    93.8 KB · Views: 51
  • IMG00178.jpg
    IMG00178.jpg
    101.7 KB · Views: 36
Last edited:
Well, I know for sure that the blue issue is nothing with the gameboards. After letting the game sit for about 30 mins I turned it back on and the screen was perfect again for about 3 minutes... then it went blue. Like last time it was still playable, just blue. I tried the brightness on the flyback and there was no change in the blueness. Wiggled the RGB/gnd/sync wires and nothing changed. I then pulled the RGB wires from the pcb and the screen went completely blank, except it was all blue instead of black. So at least I know it is something on the chassis/tube.

I really need to pick up a cap kit for this. Any other things to check?
 
Alright, I've done multiple cap kits but never installed a new flyback... I assume this is what I'm looking for from Bob Roberts? K7000 Flyback Repair Kit - $26 (1 Flyback Transformer, 1 Cap Kit, 1 HOT (2ST1398), & 1 Fuse). Is it worth it to pick up and replace the HOT and Fuse that come with this kit even if they aren't currently failing?
 
By the way, Dave, thanks for the responses thus far.

Although I've come to expect it, I hate picking up a new "working" game that ends up needing work. I just want to play it then work on it when I get the initial excitement out of my system. Oh well... :)
 
Alright, I've done multiple cap kits but never installed a new flyback... I assume this is what I'm looking for from Bob Roberts? K7000 Flyback Repair Kit - $26 (1 Flyback Transformer, 1 Cap Kit, 1 HOT (2ST1398), & 1 Fuse). Is it worth it to pick up and replace the HOT and Fuse that come with this kit even if they aren't currently failing?

The experts are split on this question for the most part. Me, I would replace them and keep the old ones for backup spares.
 
Looks like your blue gun in your tube is acting up or at least the blue drive circuit.
 
Looks like your blue gun in your tube is acting up or at least the blue drive circuit.

That was my thought... I just don't know enough about the way monitors work beyond the little I have learned. I have a cap kit and flyback ordered from Bob Roberts so regardless the chassis will get those replaced. Am I correct in assuming that if the Blue gun is "acting up" this is a tube issue that would need a rejuvenator to hopefully get things back in order? Where would I look to check on the blue drive circuit?
 
id do this..
cap it... needs it anyways... worst case youll have a good chassis as a spare or to sell...

you need to test that tube with a rejuv...(my gut says you have a intermittent short in that blue gun in the tube)


how far is eau claire from like the beloit wi/rockford il area???
If your not too far and willing to make the trip id be more then happy to test and zap that tube for you(as long as its a 10 pin tube)


now if the tube tests ok you could try swapping the blue pots with the red ones... swap the blue drive transistors with the red ones, etc... swap stuff out to attempt to isolate the problem...
 
I've got the cap kit/flyback on the way from Bob Roberts now. I'll get that installed this weekend and hope that takes care of the issue. I already have a local buddy who is going to hook me up with another 19" monitor that I can throw in my game for the time being so that I can play it. So if it ends up being a tube issue I will have to find someone to test/rejuv it. I don't know anyone in the immediate area but I may check a couple local tv repair places as I've been told they may be willing to help me out. Otherwise, like you said, I will have a nice working chassis available for sale. :) I really hope it works out, as I've said before, because when the monitor was working it was absolutely pristine. Just gorgeous. Oh well...
 
Alright, got the cap kit and new flyback installed yesterday and the monitor looked great (see 1st pic... colors haven't been adjusted perfect but you get the point). Left the game running just to see if anything came about and sure enough, about an hour in the monitor changed (see pic 2). It's almost as if the yellows or greens just aren't there now. A lot of reds but nothing like the amount of blue in the first post. So here is where I sit now... any ideas?
 

Attachments

  • IMG00183.jpg
    IMG00183.jpg
    100.6 KB · Views: 33
  • IMG00184.jpg
    IMG00184.jpg
    94.5 KB · Views: 36
When you did your cap kit, did you look over the green circuit on the neckboard?

Here's something to try:

The next time it goes blue on you, get a mirror or a friend, then gently apply pressure on the neckboard to the left, right, up, and down. See if your picture goes back to normal. If so, then you have a loose pin in your neck socket.

If that doesn't do anything, gently wiggle the three drive transistors on the neckboard. If your green comes back, shut everything off, pull off your neckboard, and reflow the solder to that transistor.

If that doesn't do anything, try wiggling the video input connector to the monitor. Sometimes you'll get a pin in there that isn't making good contact, or that the wiring to the pin is barely hanging on....
 
I had the problem with a monitor (kortek), but the problem with it was a cold solder joint on the pull-down resistor for the red gun (mine was turning red).

Resoldered that and it was good to go.
 
Had the day from hell yesterday so I never got a chance to try these recommendations... maybe tonight.
 
Here's a bump fresh from page 9.

Finally got a chance tonight to play around a bit. I found the culprit. (see attached pic). When I wiggle the wires going into the connector the colors change. When I press down on the connector (the RGBGnd, not the sync) I can get the picture looking great but as soon as I let up on it the screen goes back to sucking. I've re-pinned all 6 wires and that did nothing. It's like a number of the pins aren't making contact with the pins on the chassis. Would it be worth it to pick up a new 10-pin connector to try that? I don't see what that would change if for some reason the pins aren't making good contact. I'm tempted to just solder the damn wires to the pins on the chassis. Any ideas?

I realize I'm going through a lot of crap for a game that isn't that great but the kids dig it so it will have to do until I can afford a better driving game. :)
 

Attachments

  • IMG00190s.jpg
    IMG00190s.jpg
    89.5 KB · Views: 28
The solder connections of that male header input connector on the monitor main board need to be resoldered.

So you're thinking cracked or loose solder joints on the header input connector on the chassis? I will pull it out and take a look/reflow the solder tonight.
 
Back
Top Bottom