WG 25k7184 jitters/jumps

gutz

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I have a 25k7184 that had a vertical jump/bouncing picture of about 1/8". I could not adjust this out. The sync is hooked up correctly and I have swapped game boards and the problem is still present.

So I have tried (over the course of 3 weeks):
1. Full cap kit. All electrolytics have been replaced including B+ filter cap. (I got my ESR meter after the cap kit, would have been nice to measure the ones going in and coming out)
2. Touched up cold solder joints on main board and neck board.
3. Desoldered/soldered the wires on the main board for the remote board as they looked stressed.
4. Replaced the flyback (It had the weird black "bleeder" box on the monitor frame that was part of the flyback. It was a real pain when pulling the chassis and it had a few cracks so I swapped it out)
5. Tried 3 different remote boards to see if I had bad pots (all 3 still had the jump).
6. B+ voltage is 131 Vdc at R301 and pin 4 of IC4.

All of these have improved the picture quality (it looks REALLY good) but it still jumps! The jump has gotten better from the repairs. The monitor will run flawlessly for a few minutes, then jump for a few minutes, then go back to perfect. I have noticed that when it jumps there is a skinny horizontal wrinkle/ripple across the screen about 1" from the bottom Whenever that wrinkle is present it starts to act up. It might be a clue.

Working through the flow charts, the B+ should be 123 and if it reaches 135 the regulator should be replaced. Mine is steady at 131 (before and during jumps); would a slightly high B+ cause the pic jump? I might try swapping IC4 next.

Any other ideas out there? This is your chance to school a noob :)
 
Your B+ is right.... the 123v is for a 19", a 25" is typically 130v.

Does yours have the 50/60Hz pot on the main chassis ? Might try tweaking it a little and see.
I'm assuming you checked the solder joints on the video input header pins as well when you were touching things up.
 
Kevin - Thank you for the clarification on the B+ voltage. I will leave IC4 alone. There is a 50-60 Hz pot and I have not tried adjusting it since the repairs (it did not affect the problem prior to repairs). I can't remember if I touched up the video connector pins. I have had this chassis in/out so many times that it wouldn't hurt to do it again.

Peale - Listen to the chassis while the pic is jumping? any particular area of the chassis?
 
Kevin - Thank you for the clarification on the B+ voltage. I will leave IC4 alone. There is a 50-60 Hz pot and I have not tried adjusting it since the repairs (it did not affect the problem prior to repairs). I can't remember if I touched up the video connector pins. I have had this chassis in/out so many times that it wouldn't hurt to do it again.

Peale - Listen to the chassis while the pic is jumping? any particular area of the chassis?


I would guess listening for flyback arc or a similar arc.
 
I don't think the brand new flyback is arcing. And the new flyback didn't change the jump issue. I can only work on games during the weekends so I will try what has already been mentioned and report back.
 
I couldn't hear anything out of the ordinary from the chassis. It sounds the same as my other k7000. The 50-60 Hz pot adjustments did not fix the issue. I touched up the solder on the video connector pins and all the wire connectors on the neck board,

AND

the jump is gone! So far so good. I hope its gone for good because it was driving me crazy.

Thank you for all of the help!
 
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