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Hantarex polo/2 side of screen squashed
Harlock:
Hi, I bought an arcade cabinet lately and it came with a 25'' inch crt with a Hantarex polo/2 25-28 chassis.
My issue is tha the image is kinda squassed in the far right side and a bit in the far left side (attachements for example) , I tried to play abit with the horizontal position and size pots it didn't help,
what else should I try? Try to change caps? should I find a replacement (someone on ebay said that "MOTRAX 1570 Moniteur Chassis 25-28 " is a compatible
replacement)? Is there a setting on the chassis board that I am missing, there are some extra pots that I am not sure what they do but they are not labeled.
Thanks in advance.
grantspain:
maybe someone messed with the linearity coil, which is a adjustable
princess prin prin:
Bad linearity at the sides vs middle is due to a wrong value of the s-correction cap. If it's a 15KHz chassis the s-cap is C97 behind the flyback transformer. If the value of this cap is lower than it should, the sides get more squashed than in the middle. If the chassis is running with the original tube, check the value of C97 and if it has gotten much lower than the nominal value, replace it with one of the same value. If the chassis has been mated to a different tube and the value of C97 is good, replace the cap with a higher value one (e.g. 470nF ---> 560nF or 680nF).
If it's a 15-25KHz chassis, there are two more s-caps on the switch board (the small vertical board under the power supply cage) that are put in series with C97 depending on the selected frequency (C4 for 15KHz and C6 for 25KHz). If the issue happens only at one frequency you need to check the value of the cap relevant to that frequency. Once the issue is mostly fixed (vertical lines are equidistant on the left side and in the middle but slightly more squashed on the right side), you need to adjust (rotate) the magnet at the base of the linearity coil (L11) with a custom plastic tool that you can make yourself (just don't use a metal one).
Harlock:
@
--- Quote from: princess prin prin on May 13, 2022, 01:43:55 pm ---Bad linearity at the sides vs middle is due to a wrong value of the s-correction cap. If it's a 15KHz chassis the s-cap is C97 behind the flyback transformer. If the value of this cap is lower than it should, the sides get more squashed than in the middle. If the chassis is running with the original tube, check the value of C97 and if it has gotten much lower than the nominal value, replace it with one of the same value. If the chassis has been mated to a different tube and the value of C97 is good, replace the cap with a higher value one (e.g. 470nF ---> 560nF or 680nF).
If it's a 15-25KHz chassis, there are two more s-caps on the switch board (the small vertical board under the power supply cage) that are put in series with C97 depending on the selected frequency (C4 for 15KHz and C6 for 25KHz). If the issue happens only at one frequency you need to check the value of the cap relevant to that frequency. Once the issue is mostly fixed (vertical lines are equidistant on the left side and in the middle but slightly more squashed on the right side), you need to adjust (rotate) the magnet at the base of the linearity coil (L11) with a custom plastic tool that you can make yourself (just don't use a metal one).
--- End quote ---
If I am not mistaken, my chassis is a 31khz since it outputs SVGA, although I thing this is the card you are mentioning (first picture), do those pots do anything? or should I just go ahead and start to changing caps? I can't be sure but it seems like monitor/cabin/chassis are all the original pair. Crt doesn't have any stickers on it though.
--- Quote from: grantspain on May 12, 2022, 12:36:50 pm ---maybe someone messed with the linearity coil, which is a adjustable
--- End quote ---
Btw, I played around with the linearity coil and it didn't fix anything (black thingy next to fan).
princess prin prin:
OK, you have the VGA/SVGA version (31KHz and higher). The sticker says the chassis is made for a Philips A59EAK552X44 tube (25"). The yokes on Philips tubes have a characteristic design that can't be confused with that of other manufacturers. If it looks like this it's a Philips, if not post a pic.
You'll have to remove the fan to see C97. It's not an electrolytic cap, it looks like a little box. The blue square is where the caps on the frequency switch board are and the red square is the linearity coil. It can be adjusted by turning the magnet at the bottom.