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FIXED - CRT Top of the screen folding over?

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LTC:
I know it's probably a long shot and sorry for the vague description, but it's the best I could come up with. The top of the screen looks like it is folding over itself, is the best way I can describe it. Any idea what may cause this?

If you look at the top, SCORE and HISCORE are upside gown, and during game play, when the enemies approach, you can see the start right where the lines on the screen appear. They go up, before entering the playfield from the top, so it looks like the screen folds over itself at the top.

princess prin prin:
It's a cap that's failing in the vertical deflection circuit. I can point it out to you if the schematics are available. If not, I need pictures of the chassis, top and bottom side in the area where the vertical IC is located.

LTC:

--- Quote from: princess prin prin on June 14, 2025, 04:53:46 pm ---It's a cap that's failing in the vertical deflection circuit. I can point it out to you if the schematics are available. If not, I need pictures of the chassis, top and bottom side in the area where the vertical IC is located.

--- End quote ---

Thank you for the reply. I believe this may be the schematics of the chasis.

Zebidee:
What you have there is indeed generally called "vertical foldover" and is an early stage of vertical collapse - the TV is having problems expanding the picture out from the middle. The fact that it has not "collapsed" completely tells us the vertical IC is probably OK, and (as Princess has pointed out) most likely failure points will be supporting electrolytic capacitors (little aluminum cans) as their electrolyte dries out eventually.

Most CRTs are approaching an age (15-20+ years) where capacitor failures are likely. Many people will just recap the entire board, but usually you don't need to change all the caps. Trouble is, sometimes failing capacitors are obvious (e.g. exploded or leaking), but sometimes they look perfectly normal.

You might want to invest in an ESR (equivalent series resistance) meter, with which you can check the health of electrolytic capacitors without removing them from the chassis. Failing caps usually develop high resistance (ESR) which the meter measures. If ESR is too high, replace.

ESR meters to look for include any made to the Bob Parker/Dick Smith/Silicon Chip design (e.g. for a classic look https://www.altronics.com.au/p/k2574-esr-meter-kit/, or the blue Anatek one which looks different but is the same design). There are others out there on the market too. Shouldn't cost you more than about US$110 or so, maybe cheaper.

I used to have about 8 of the original Dick Smith ESR meters (kit form) in my shed, but haven't been able to find them lately. Worried they might have been thrown out accidentally.

Your vertical deflection IC is IC401, 7 pins. Looks like a long rectangle with a corner sliced off. I see a couple of electrolytics there (470uF and 100uF).

princess prin prin:
This is the cap I was talking about, C432 100uF 35V (+ to pin 3, - to pin 7). This cap is in that part of the vertical IC called flyback generator (or booster or pump-up). When the scanning period is completed and a frame has been drawn, the beam must be brought back ("fly back") from the bottom to the top where another scan period will start. During the scanning period the IC works with a 24V supply (on pin 6). In the flyback or retrace period it works with a higher voltage, not supplied externally like the other but generated by the IC itself. If the cap connected to the flyback circuit loses its capacitance, the beam doesn't make it to the top and so you have the foldover issue.

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