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Author Topic: Hantarex polo/2 side of screen squashed  (Read 402 times)

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Harlock

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Hantarex polo/2 side of screen squashed
« on: May 12, 2022, 07:24:11 am »
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

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Re: Hantarex polo/2 side of screen squashed
« Reply #1 on: May 12, 2022, 12:36:50 pm »
maybe someone messed with the linearity coil, which is a adjustable

princess prin prin

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Re: Hantarex polo/2 side of screen squashed
« Reply #2 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).

Harlock

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Re: Hantarex polo/2 side of screen squashed
« Reply #3 on: May 16, 2022, 06:36:12 am »
@
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).

 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.
 
maybe someone messed with the linearity coil, which is a adjustable

Btw, I played around with the linearity coil and it didn't fix anything (black thingy next to fan).


princess prin prin

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Re: Hantarex polo/2 side of screen squashed
« Reply #4 on: May 16, 2022, 08:23:22 am »
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.

« Last Edit: May 16, 2022, 08:25:09 am by princess prin prin »

Harlock

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Re: Hantarex polo/2 side of screen squashed
« Reply #5 on: May 16, 2022, 09:05:39 am »
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.

I created a tool and played a bit with the linearity coil you showed me, tried turning it both ways but it just shrinked the whole image horizontally. My monitor for sure it's not like the one you showed me btw.
What should I do now? change the C97? to the same cap value (film capasitor 0.18uf/400V)? try anything else? Thanks again for your help.

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Re: Hantarex polo/2 side of screen squashed
« Reply #6 on: May 16, 2022, 10:42:11 am »
That's a Panasonic tube so we can't be sure the value of C97 is correct for it. If you have a capacitance tester measure it and see if it has decreased a lot. Alternatively, get a few caps of increasing value and try them until the sides are as wide as the middle (a vertical bar test pattern is more helpful than in-game pictures). Try: 0.18, 0.27, 0.36, 0.47 (depending on where you buy them, the value could be in nanofarad so 180, 270, etc.). It's important that the voltage rating is the same (400V) and also the lead spacing (22.5 mm).

Harlock

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Re: Hantarex polo/2 side of screen squashed
« Reply #7 on: May 16, 2022, 11:35:00 am »
Thanks a ton, I will give a try and come back at you

Harlock

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Re: Hantarex polo/2 side of screen squashed
« Reply #8 on: May 20, 2022, 09:07:15 am »
That's a Panasonic tube so we can't be sure the value of C97 is correct for it. If you have a capacitance tester measure it and see if it has decreased a lot. Alternatively, get a few caps of increasing value and try them until the sides are as wide as the middle (a vertical bar test pattern is more helpful than in-game pictures). Try: 0.18, 0.27, 0.36, 0.47 (depending on where you buy them, the value could be in nanofarad so 180, 270, etc.). It's important that the voltage rating is the same (400V) and also the lead spacing (22.5 mm).

Hey, I think It worked, although previous capacitor was fine, I bought some mkt capacitors (Actually it needed mkp, but I made a mistake and bought mkt ones although mkt worked for testing), I soldered some posts in order to try different ones, 0,366nF and some width twiking seems to do the trick.
It still has some slite weird quirks, like for example 2-3 brigther lines at the far left but they are hardly noticeable, the result is soooo much better than before and I really thank you that you helped, you are a true wizard in this area.
The only alarming thing I noticed through testing is that with larger C97 capacitor, the capacitor is getting hotter (yes it is rated for 400v) with using pandora box vga output, but it gets like A LOT hotter when I use a vga output from a laptop or a GBS-8200 (cga to vga converter). Although if I solder it on the proper side of the chassis it is almost under tha fan so it will help.

Also I think I created a tiny bending on the sides when I was testing linearity coil setting that can't get rid of with cushion pot, I will fix it probably with some more tweeking.
But overall it I am much happier with the result than before, I can't even grasp how you knew about the specific capacitor.  :applaud:

princess prin prin

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Re: Hantarex polo/2 side of screen squashed
« Reply #9 on: May 20, 2022, 01:16:40 pm »
It still has some slite weird quirks, like for example 2-3 brigther lines at the far left but they are hardly noticeable

Check the solder joints of R142 in parallel with the linearity coil. It's a fact that without that resistor you get a jailbar/ringing effect at the left side. As it's pretty tall maybe it got knocked when you adjusted the coil?

The only alarming thing I noticed through testing is that with larger C97 capacitor, the capacitor is getting hotter (yes it is rated for 400v) with using pandora box vga output, but it gets like A LOT hotter when I use a vga output from a laptop or a GBS-8200 (cga to vga converter). Although if I solder it on the proper side of the chassis it is almost under tha fan so it will help.

Not sure but I suggest to improve the solder joints of the 4-pin green header that connects C97 to the frequency switch board. Also, I see a lot of dust build up around the horizontal output transistor T22 that you better blow off to make it run cooler.

I can't even grasp how you knew about the specific capacitor.  :applaud:

Other monitors have this cap too so if you have the same issue you know what to look for.