What could cause this h.linearity issue?!

[keropi]

Hiya!

I have a 14" 15/31k dualsync monitor, when pin15 on vga connector is high then the monitor switches to 15k mode.
But I have this annoying linearity issue - right side is compressed:



in VGA mode it's OK - you can't expand it to full screen , this is a 640x480 max resolution monitor and it has black bars around like all old vga monitors...



So what I tried:
- replaced all electrolytic caps because there were some brightness/contrast issues which are now gone
- replaced all mylar caps in hopes the h.linearity issue will go away
- tried 6.6nf instead of 7.5nf for sweep capacitor C526 in hopes it would affect the issue - it did not
- tried adjusting the horizontal coil but the compressed part just remained the same

full-resolution: https://i.imgur.com/IIxNI63.png

Could it be:
IC101 TA8631N (LINEAR RGB PROCCESSOR)
IC402 TDA1675A (VERTICAL DEFLECTION CIRCUIT, most likely no)
IC401 HA11235 (Synchronous Signal Processing System that is also the horizontal oscillator among other functions)

Any ideas/tips will be greatly appreciated! Thanks!!!

[keropi]

well replaced all those ICs, no change
any ideas please share

[keropi]

Just an update to bring closure to the issue - with the help of online friends the issue was found : it is capacitor C521 that is a S Correction one in 15k mode.
Original is a 470nf/200v one - replacing it with a 2.2uF capacitor the monitor's 15k h.linearity improves and now it's tolerable. Not perfect but you cannot notice it during gameplay.
I count this as a win for this monitor



monitor is not yet centered in the above pic but the improvement is quite visible

[geotrig]

Yeah big difference there well done