Nanao MS8-29 Image issues

[gianka]

I have a Samsung A68KVL74X01 crt monitor and a nanao ms8-29 chassis.
The image has these problems (look at the photos) :
There are vertical lines that narrows the image in the upper part of the crt (on the left side in my case); as you can see from the photos, the squares on the left are flatter than the right ones.
Another problem is the bad regulation of the SPC pot. Maybe it is related to the first problem.
what could it depend on?
how can i fix the problems?
Thanks

 

[ShootTheCore]

Have the capacitors been replaced on the chassis board? Those “rollover” symptoms match what happens if the caps in the geometry section aren’t regulating properly.

Does the geometry change after the display has been on for 20 minutes? If so, it definitely needs the caps replaced.

EDIT
Looks like the C433 capacitor and R433 resistor regulate edge rollover.

https://wiki.arcadeotaku.com/w/Nanao_MS8-29#Manuals

 

[Kidkaos]

Nice. One of my ms9s does this streaking "roll over" effect and was wondering if just a cap kit would fix it.

 

[nem]

Nice. One of my ms9s does this streaking "roll over" effect and was wondering if just a cap kit would fix it.

That's definitely cap related.

 

[gianka]

Have the capacitors been replaced on the chassis board? Those “rollover” symptoms match what happens if the caps in the geometry section aren’t regulating properly.

Does the geometry change after the display has been on for 20 minutes? If so, it definitely needs the caps replaced.

EDIT
Looks like the C433 capacitor and R433 resistor regulate edge rollover.

https://wiki.arcadeotaku.com/w/Nanao_MS8-29#Manuals

yes the capacitors have been replaced ( only the ones in the area of the vertical - look photo: precisely c438, c431, c432, c521, c422,c913 and c911 )
No, the geometry doesn t change after the display has been on for 20 minutes

EDIT
Looks like the C433 capacitor and R433 resistor regulate edge rollover.

If you look at the pictures there isn't any C433 capacitor (and any R433 resistor) ; that's normal looking at the schematics. So how could i fix it?

This chassis has been repaired and this problem remained. It didn't turn on at first.

Anyway it is important to fix my first problem : "vertical lines that narrows the image in the upper part of the crt"
thanks

 

[nem]

Your vertical linearity is definitely off. Have you tried adjusting it?

Also, the pot has been replaced. It should be 1kohm. Check that the replacement pot matches that.

EDIT: trapezoid adjustment is on "card 1". It's the one with the metal rotating contact, VR1. That should fix one of your issues.

 

[gianka]

Your vertical linearity is definitely off. Have you tried adjusting it?

Also, the pot has been replaced. It should be 1kohm. Check that the replacement pot matches that.

EDIT: trapezoid adjustment is on "card 1". It's the one with the metal rotating contact, VR1. That should fix one of your issues.

Thanks for your replies.

yes I had already tried all the pots ' adjustments; in particular adjusting the V.Lin pot, the size of the letters becomes larger or smaller as described in the manual (look picture). This does not solve the first problem; then adjusting the trapezoid pot nothing happens, precisely the image shakes slightly but the irregularly arched lines don't change. I think that if i don't resolve the second problem (spc pot) I can't see the trapezoid change. Maybe the trapezoid pot could not work well too.
Instead if I turn SPC pot in the reverse direction the edges of the image become concave in the sides of the screen (up and down in my case) as you can see in photo (it is not my picture)

yes the pot has been replaced and it is 1kohm. Anyway the problem already happened before changing V.Lin pot (VR432)

so the cause of these problems seems to be a mistery (or very difficult to fix).

 

[AussieSR]

Digging up an old thread, but did you find a fix to these issues? I'm experiencing a similar tearing issue on an MS8-29

 

[sLpFhaWK]

i seem to be having this issue as well and it was all recapped recently.

 

[AussieSR]

i seem to be having this issue as well and it was all recapped recently.

So this might help... mine has been resolved thanks to Jomac. Turned out the yoke wasnt quite right for the MS8-29FSG chassis. The resistance and inductance all measured up exactly the same as what was listed online for other MS8-29FSG yokes, but Jomac suggested it was from an MS9, and to put a 1k resistor across the vertical coil. He was absolutely spot on. 1k resistor fixed this issue for me perfectly!

 

[sLpFhaWK]

So this might help... mine has been resolved thanks to Jomac. Turned out the yoke wasnt quite right for the MS8-29FSG chassis. The resistance and inductance all measured up exactly the same as what was listed online for other MS8-29FSG yokes, but Jomac suggested it was from an MS9, and to put a 1k resistor across the vertical coil. He was absolutely spot on. 1k resistor fixed this issue for me perfectly!

hmm i dont know if i'm qualified to do that, i don't know where that is as well. ill do some research and see, we're gonna pull the monitor and recalibrate it based on one of @Viku 's video from youtube and hopefully see if this fixes it.

 

[Viku]

hmm i dont know if i'm qualified to do that, i don't know where that is as well. ill do some research and see, we're gonna pull the monitor and recalibrate it based on one of @Viku 's video from youtube and hopefully see if this fixes it.

 

[sLpFhaWK]

@Viku got the issue squared away today, it was an external issue that was messing us up and once it was removed everything worked perfectly but since we had the crt out of the cabinet we still used your video to dial it in and now the display looks fantastic.

Thanks again for having that video out, its a great source to use to dial in the calibration!