Hantarex polo 25 calibration

[Ravi_s]

Hi Guys,

Just picked up a mame cab over the weekend, which has a Hantarex polo 25 monitor. The image appears to get blurred when I turn up the brightness/contrast.. there appears to be, too much white. I can get a sharp picture by turning down the brightness or contrast but this results in dull colours / slightly washed out image. I can get around this by tweaking the Groovy mame slider controls - dropping brightness slightly and dropping the gamma between 850 - 700. This results in a sharp, colourful image but too much contrast - darker colours then normal so the game is missing details.

Please see the attached pics arcade front end - no tweak, metal slug - tweaked slider controls gamma 750.

Is it worth me dialling down the white pot or tweaking the monitor focus?

https://postimg.org/gallery/1a7voskqu/

Thanks for your help.

 

[tb2000]

Try this - get a game screen or testcard with a black background, turn the brightness up full, contrast to minimum, then adjust the screen pot on the flyback/lopt on the chassis till the flyback lines disappear (these will show as falling horizontal lines), then. Knock it back a bit more till the background is pretty much black. Then bring up the contrast and see how it looks.

Edit: also, put all game settings on standard gamma or whatever, and only try this when the monitor is fully warmed up, so after at least about 20 minutes of being switched on. You may need to tweak the focus pot as well to get a sharp picture when you've sorted the other problem.tb20002017-09-12 11:13:03

 

[Ravi_s]

Thanks - Sorry I am a novice - Screen pot? it that the top one focus or bottom one for white?

 

[tb2000]

Assuming you know what the flyback transformer/lopt is, its the lower one. It nearly always says "screen" below it as it actually adjusts the screen voltage which in turn adjusts the main brightness.

Edit: and if you're new to this make sure you're careful working round a live monitor!tb20002017-09-12 11:16:05

 

[Ravi_s]

Thanks - I will give it a go!

I am been around retro gaming a while .. yeah I know not to pick a fight with a high voltage CRT !!!!

 

[Ravi_s]

Thanks for your help! I managed to tweak the screen and focus pots using a mirror and the picture is much much better!!!