wells gardner k7500 chassis 25" philips CRT jumpy

[CLAPTON54]

I am working on full size Midway arcade The Grid. Picture is hour glassed on left side and jumps to right horizontally. over all picture is good. I am considering recapping chassis but am not sure if this is best move. Chassis is still in unit. In have not worked on CRT before, but know how to safely discharge. Have repaired several LCDs and am pretty handy with most repairs. Looking for advise. Thanks.

[freakaftr8]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

Check your main filter caps on the b+ side. Thats a start. If leaky your horizontal oscillator will be off. Is there any crawl in the picture?

[freakaftr8]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

also be super careful there's 25,000 volts that chassis! stay away from that big red wire going to the top of the picture tube. they hold a nasty charge and it will bite you.

[CLAPTON54]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

If by crawl you mean not not staying in frame, no. The picture is steady except for the horizontal spikes. It is very evident when in the adjustment mode with the grid. Vertical lines to have small spikes intermittently. Horizontal lines seem steady. I'll post some pictures perhaps you can point out the cap you are referring to. Not familiar with terminology of b+. Thanks

[CLAPTON54]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

pictures of chassis and tube. Please help ID the B+ side main filter cap.

[freakaftr8]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

Is the screen out of focus at all? B+ are boost capacitors that operate the high voltage aspect of the monitor. Post a pic.of the screen and tge test grid with the problem

[CLAPTON54]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

Added pictures of the picture with adjustment grid. One good, one jumping.

[freakaftr8]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

Thats not at all what I thought I t was doing. Check horizontal centering adj knob gor crap in it adjust it back and forth and see if the thing get s jumpier.

[CLAPTON54]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

Finally had a chance to check it out. It does appear to reduce the jumpiness when I turn the adjustment all the way to the right and jet more jumpy when I turn all the way to left. I have two more of these games and I will try to switch the vontrol board to see if it improves. I think it just plugs in. If you have more suggestions mI would appreciate it. I'll let you know the results.

[CLAPTON54]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

I switched the control boards and got same results and other unit was good, so the board is eliminated, but may be the horizontal hold circuit.

[freakaftr8]

Re: wells gardner k7500 chassis 25" philips CRT jumpy

I bet you have some drifting resistors in the horizontal hold or horizontal oscillating circuit. what you should do is take a can of freeze spray and freeze each one of those resistors the big ones and see if the problem straightens out if it does you found it.

just as a precaution turn the monitor of what you do this then turn it on when you're done spraying