WG K7000 25" - Random pops and flashes in the neck

[johnczerwinski]

I have a weird one that I've never come across, and can't find a lot on it.
It's a WG k7000 25" (P538). After a few minutes turned on, I hear pops, see flashes in the neck tube, and the picture flickers.

Here's what I've done so far:
1. New flyback, new caps, reflowed/soldered the neckboard
2. Cleaned the neck board crt socket
3. Checked neck board ground to DAG
4. B+ at 130v
5. Check the tube with a B&K rejuv. No shorts or leakage. I've run other k7000 chassis on this tube/yoke combo without any issues.

Where else do I check?

Video here

https://www.facebook.com/video.php?v=946036616776891

 

[curtislv426]

You could switch in another neckboard or solder in a new cr23 socket. That's what I would do.

 

[therealgary]

Sounds like a dirty anode cap, but you replaced the flyback. Odd. Please update us once you find the issue as I'm curious what's causing it. Is it possible you have a bad new flyback?

 

[johnczerwinski]

Yeah, I'll probably try another flyback, since I have a few in stock. I ordered a few CRT sockets, as I didn't have any new ones

 

[johnczerwinski]

Not that I "solved" the issue, but found out what's causing it.
The KB and KG show "leakage" on the B&K 467, which doesn't look like it can be fixed.
I verified it's these two guns by turning over both green and blue guns (leaving on the Red - Full Screen). NO Popping! Ran it for hours. Turned off the monitor, to cool it down. Did it again. NO popping
Turn on just the Green. Popping!
Turn on just the Blue. Slight popping
Turned both Green and Blue (keeping red off). Popping

I did clean and balance, and seemed to reduce the popping effects. In fact, if I let it run for a while, it stopped popping.
If I turned it off for 20 mins, turned it back on there would be some popping but it would end up stopping after a while.

Conclusion:
Not a chassis issue. Tube's green and blue cathode have some kind of leakage between them.

 

[therealgary]

Leakage would absolutely cause it. When you said other chassis didn't cause the issue, I kind of ruled that out. Thanks for updating and I guess we all learn something new every day. A bad tube is a little unusual so I have to think it was mishandled somewhere, somehow. Could also just be a very small vacuum leak. Perhaps a manufacturing defect that finally showed itself.

 

[ArcadeTechGW]

Try this:
Remove the entire chassis from the game.
Put down carpet, foam on the floor.
Set the chassis TUBE DOWN on the carpet / foam on the floor.
Now GENTLY tap the neck of the game with a screwdriver handle. You are trying to create gentle shocks to knock loose any shorting materials, which will fall to the screen below. (Don't freak out - think of the GEOMETRY).
Do this for around a minute, working your way around the tube. This is tap, tap, tap, not TAP TAP TAP. The glass is thin, be careful.

Now you are done. Roll the chassis to level. Anything you knocked loose is now falling to the bottom of the tube face, and out of the line of fire of your electron guns. Tap the center of the screen with something soft, again tap, not TAP to knock anything loose.

Now pick the chassis / tube up, keep it as LEVEL as possible, and re-install it in the game. Secure it by the usual bolts/screws.

Re-connect everything, and wait a day (for gravity to also help). Now power it up and report back here.

Questions: Did you ship the game at any time on it's back?

 

[johnczerwinski]

Leakage would absolutely cause it. When you said other chassis didn't cause the issue, I kind of ruled that out. Thanks for updating and I guess we all learn something new every day. A bad tube is a little unusual so I have to think it was mishandled somewhere, somehow. Could also just be a very small vacuum leak. Perhaps a manufacturing defect that finally showed itself.

That threw me off too. I had two chassis that didn't do it. This tube is used for my test rig and I do move it a lot. Maybe one of those moves jarred some schmutz loose.

The other thing, I tested the tube in the very beginning and didn't show any issues. Could be that it had to warm up before showing any signs.

 

[johnczerwinski]

Try this:
Remove the entire chassis from the game.
Put down carpet, foam on the floor.
Set the chassis TUBE DOWN on the carpet / foam on the floor.
Now GENTLY tap the neck of the game with a screwdriver handle. You are trying to create gentle shocks to knock loose any shorting materials, which will fall to the screen below. (Don't freak out - think of the GEOMETRY).
Do this for around a minute, working your way around the tube. This is tap, tap, tap, not TAP TAP TAP. The glass is thin, be careful.

Now you are done. Roll the chassis to level. Anything you knocked loose is now falling to the bottom of the tube face, and out of the line of fire of your electron guns. Tap the center of the screen with something soft, again tap, not TAP to knock anything loose.

Now pick the chassis / tube up, keep it as LEVEL as possible, and re-install it in the game. Secure it by the usual bolts/screws.

Re-connect everything, and wait a day (for gravity to also help). Now power it up and report back here.

Questions: Did you ship the game at any time on it's back?

Thanks, I'll give that a try and let you know. I obtained the monitor by itself, not from a game, so there's no telling if it was shipped on it's back.