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Sparks around anode - works fine after warm-up

I have a pretty bad monitor problem that so far I can't find a solution for. Here's the details:

Wells Gardner k7000, 25" (Mounted in an arcade cabinet, connected to a WinXP PC) New cap kit, replaced flyback Applied corona dope around anode connection (directly on glass)

When started up from cold, the flyback squeals and there's a "fizzing" or "crackling" sound coming from the back of the tube. After about 15 seconds, the monitor display looks skewed and is rolling very bad, sort of like trying to run it at an unsupported resolution. The display doesn't cover the whole screen; there's probably 10% on the bottom that is black.

After about 60 seconds the flyback has quieted down and "fizzing" is less noticeable. Though the smell of ozone is very aparent now. The display slowly moves out till it is filling the monitor, and the picture stops rolling yet is still totally skewed and garbled.

After about 100 seconds the display jumps to perfectly correct, maybe with the whites being a bit dull and yellowish. The fizzing is still happening, though you really have to listen for it. From this point on, the monitor looks great and works more or less correctly.

Its obvious that something is "warming up" during all of this, and behaving better once it gets there, but I have no idea what it is. I'm thinking that maybe the secondary HV is way too high, but I have no way of testing this. The chasis has a new flyback and cap kit, though I know there are more caps on there that weren't in the kit (notably one that is as big around as a quarter). Can anyone diagnose this from my description?

I have placed a video of this up on my website in DivX format. Here's two links, one further compressed for quick download:

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If anyone can help with this I would really appreciate it. I am afraid to bring this cabinet into my house in this condition.

Reply to
jamesferrell
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My first guess is a bad flyback transformer. I would also look into electrolytic capacitors since they tend to get better as they warm up. A can of freeze spray is a great troubleshooting aid for problems like this.

Reply to
James Sweet

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The flyback transformer is new, replaced it along with the cap kit.

Do I just hit some of the caps with the freeze spray and watch for a reaction?

Reply to
jamesferrell

Let it warm up until the problem goes away, then just start hitting various areas of the board with a quick shot of freeze spray and see if you can get the problem to reappear. If you did a cap kit that should have covered it, it could be a cracked solder joint though, thermal cycles do affect those.

Reply to
James Sweet

I would turn out the lights and see where the arcing is coming from. Some times a little well placed RTV does wonders. Make sure you let it fully cure though before turning the set back on again. Lenny Stein, Barlen Electronics.

Reply to
captainvideo462002

quoted text -

Yes but practice so you can just get a drop of liquid out of the tip of the spray tube onto the top of the cap. That way you can isolate it to one cap and subsequently watch the problem go away after it warms up. Hard to do this if you just blast them with a spray.

Reply to
Meat Plow

I went back at it today with a fresh perspective, and looked closely for where the arcing was happening. It was right around the anode cap, and some of the sparks were jumping a good 2" past the outer edge of the cap. I ran my finger across the glass (after turning it off, of course) and there was a little bit if grime on there. I soaked a paper towel with isopropyl and wiped the entire back of the tube clean, stopping just shy of the black spray coating at the sides. The towel was filthy; a lot of stuff came off the back of that tube.

I let it dry and fired it back up. It sparked just a little bit, and only for a few seconds, then stopped completely. I turned it on and off a couple times and it is more or less gone. Too soon to tell if this is a permanent solution, but I'm keeping my fingers crossed.

Reply to
jamesferrell

By "gone", I mean the problem is gone. The monitor is working correctly now. I read that post again and realized it might be unclear.

Thanks.

Reply to
jamesferrell

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