25” crt monitor pots help.

M4carp

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Jan 12, 2019
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David
Been trying to tune the 25” crt on my mame cab, can’t get it sharp enough for my liking, focus pot as far as it can go. As soon as I put the contrast up it loses the sharpness.
Below the focus pot is another that has a blob of something on it to keep it from being adjusted, looks like it’s says screen.
Anyone know what it does?
Other adjustments are on a board with a fly lead at the coin door, contrast, brightness, screen position, stretch.
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Vimtoman

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Sep 29, 2018
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When you say "out of focus" is it that you see the rgb on white dots?
If it is then that's the convergence out slightly.
Is it out evenly all over or in patches as that would determine what you need to do.

For all over then the Yolk rotating magnets need tweaking.
If its a patch then you may need to add a magnet strip down the back of the yolk or add spot magnets on the tube itself.

Using magnets will change the geometry of the picture and may cause patches.

Best thing to do is to get a cross hatch image in white on the screen.
Note or mark the rotating magnets so that you can go back to the original pos.
They tend to be locked with a paint ,we use to use tipex to set them as it was less permenant.
Shift the rotating magnets and adjust the rgb dots so that they align.
Use a mirror so that you can see.

Lots of stuff online on how to adjust.

Oh whoever does the adjustrment to wear rubber gloves as less chance of getting zapped.
High voltage in there so advice is not for you to do it.
Could be bad for your ticker.
 
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AlanJ

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If you can't focus it anymore most likely because the EHT circuit is drifting, dodgy capacitors most likely, need replacing. The "screen" adjustment will have been factory set. It's not relevant to adjust that for your issue.
 
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M4carp

M4carp

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Its not the convergence, although it might be out a tiny bit. I have messed with that on a Barco projector.
It’s the sharpness of the picture and seems the focus pot alters it except it won’t go any more as it’s maxed out.
The monitor was supposed to of had the cap kit fitted but when I got it home and checked, it looked like old components to me😡

When it’s cold the picture will expand and shrink a bit until it warms up so guess it is the caps, I’ve had it about 5 or 6 years now so will see how it goes.
Such a pain in the backside, I really don’t fancy talking that lead off the screen.
Doesn’t look as dotty in the flesh.

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