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Monitor vertical image size - unable to adjust "far enough"


MonoJoker

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Hi all,

 

Recently got hold of a lowboy running a 19" arcade CRT. the image height is too tall in most games to varying degrees. More of a nuisance than anything serious but for some games like Galaga or Ms Pacman it's a choice between not seeing the score at all or not seeing the bottom of screen (showing level, additional lives, bonus stuff, etc). I've tried adjusting all of the pots shown in the pics but none seem to adjust the vertical SIZE. In fact what's horizontal and vertical seems reversed anyway - the monitor is portrait mounted but vertical-size adjust the "width" of the image. And (probably related) the funny looking end pot for H-width doesn't seem to have an adjuster screw head in it.

 

Is there a trick to this or is that H-width pot something that requires more than a normal flat blade screwdriver to adjust? I'm a bit hesitant to stick anything metal up in there anyway as it might contain dangerous voltage/current? The others seem OK as they are plastic?

 

Thanks for any help.

 

20180706_122908.jpg20180706_122903.jpg

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If the monitor is vertically mounted, you want to be adjusting the H-width ferrite core. However, these things are notoriously shitty, often break and sometimes don't work at all. You do not want to be sticking anything metal inside, you need to use a plastic adjustment tool. You can order them online or buy them from Jaycar. They are called TV alignment tools, like this. https://www.amazon.com/Universal-Color-Alignment-Tool-Set/dp/B005M6BY2A

 

Basically, insert the correct adjustment tool into the H-width slot, then start turning and very closely watching the screen. You will see it slowly start to shrink or grow, it might take quite a few turns to actually see anything. If you try to turn the core one way and it doesn't turn, try the other direction. If it doesn't move at all, don't mess with it, as you could damage it.

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Possible yes. Easy? Depends on how good you are with a soldering iron. Certainly not something I would do myself, but others would. Jomac is your man for advice on replacing H-width cores. Try to adjust it first and see how you go. I've got a couple of Nanao monitors with H-width cores and they all work fine. Just don't expect it to make a massive difference. You'll be lucky to get 2cm-3cm screen size adjustment out of it.
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Sometimes there is a width jumper on the chassis often labelled W or N

If your chassis has that you could move the jumper and use the adjustments from there

Also sometimes there is an unlabelled pot on the board that adjusts the ratio between horiz & vertical

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The ferrite core slug looks to be missing from that coil entirely. It's a grubscrew shape that screws up the middle. Without it there's nothing to adjust and the image sits at maximum width. Don't stick your screwdriver in while it's live. And don't use metal anyway because it will get hot enough to burn you inside two seconds from the induction. Cheapest tools i found were the 1PK-606A set on Aliexpress.

 

A generous AA member, sadly i can't remember who, sent me a ferrite slug for my Nanao/Sega MC 2000 S. But Pat was right, you get mb 2cm overall (1cm each edge) difference if you screw the slug right the way in.

 

I'm not using the one i have, and if you want it PM me your address and i'll pop it in an envelope. I think the slugs are fairly standard between chassis, but mb someone could confirm...?

 

 

As an aside, what video source are you using? If it's a MAME cab, a much better option is to shrink and centre the horizontal width by altering the modelines the PC is using. (Monitor terms always apply to a horizontally-mounted tube. So the H-width adjustment is always going to be the long axis, which just happens to be vertical when you rotate the tube).

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Thanks everyone I'm learning a lot here. Having only played with MAME and always upgraded to LCDs for simplicity and weight saving it's not an area I'm familiar with.

 

@buttersoft it's not a MAME it's running a 40 in 1 board I believe so no software options available unfortunately. I'll send you a PM if you're still offering the grub screw and that might give us just enough adjustment to get it workable.

 

@Boots I'll have to have a look inside again and see if there is anything like you describe. Thanks.

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