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Author Topic: Geometry/Deflection Yoke Fix Question  (Read 2319 times)

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Dacasks

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Geometry/Deflection Yoke Fix Question
« on: August 18, 2018, 09:41:19 am »
I really don't expect someone to give a "presto!" answer, because, of course, CRT geometry issues have a variety of causes... but if anyone out there wants to give a shot, would be cool to learn at least.
So I got this Sony pc monitor. It's pretty rare around here to find 21'' PC crts so I got this one for a considerable, "fair" amount of money (so that's why I'm a little bit sad now, because it wasnt that cheap).
Despite being labelled as a "pro" monitor by many nameless people throughout the years on dead internet forums, the geometry on this one is pretty f* up as far as "pro" and "Sony" and "Aperture Grille" goes to my taste. Really: My Shadow Mask 997mb banged up Samsung Monitor has the same "broken a** flat screen" geometry overall (I hate flat screens).
But the biggest issue is... part of the right side of the screen appears to be slightly wider (circa 3 to 4cm from the edge seems to be circa 2mm wider than the rest of the screen, I measured) than the left counterpart. It sounds picky and doesn't seem a big deal, and it's not if you think about it... but the screen is large enough to make it hella perceivable. This basically make the Second player character buff, in comparison to the first player, for example.
Surprisingly it's barely noticeable in shooters/fast scrolling games. It's annoying in Fighting/static games though.
If this monitor was used for "CAD"as they said, then I guess there are houses with bigger bathrooms than garages out there.

QUESTION

I know that the dot pitch is not equally on both sides of a crt screen (every monitor bigger than 15" I have has size discrepancy), and “perfection” is out of question but...

Is there any possibility of a "95% chance" of a bad positioned deflection yoke is causing it? Like, if part of it is uneven with the other? I heard (and when I say heard I actually mean read) that depending of the yoke position the image can be thinner/wider, so I wonder if that’s what is causing it. Or could it be another, almost "impossible" thing to fix (like some IC responsible for the digital image adjustment)? Or at least someone could say “Just live with it. Someday someone will appear in your life and make you happy.” like a hot 60 year old lady who also appears to be tech savvy on CRTs.
Worth notice that no matter what geometry settings (and there are a ton on this thing, including convergence) I fiddle up with, it won't help.
Anyway, thanks for taking the time!
« Last Edit: August 18, 2018, 02:00:29 pm by Dacasks »

Zebidee

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Re: Geometry/Deflection Yoke Fix Question
« Reply #1 on: August 19, 2018, 02:20:37 pm »
Hi, you need to put up pics/model numbers etc otherwise nobody is sure what's going on.

Sounds like your sony's geometry is out, you can probably fix it with one of those pots you were talking about. Stay away from the actual convergence pots, from what you say your convergence (colour purity, RGB beam alignment etc) seems fine, just the ones for screen geometry (ie screen shape) like "pin" etc. You probably don't need to touch the yoke. Take a photo of the pots and post that if you want more commentary on this.

You could also take it up with the Facebook group "Sony PVM/BVM - Users of Sony Professional & Broadcast CRT Monitors". They might be more familiar with your gear. Again, pics are needed if you want responses.
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Dacasks

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Re: Geometry/Deflection Yoke Fix Question
« Reply #2 on: August 19, 2018, 04:29:09 pm »
Hi, you need to put up pics/model numbers etc otherwise nobody is sure what's going on.

Sounds like your sony's geometry is out, you can probably fix it with one of those pots you were talking about. Stay away from the actual convergence pots, from what you say your convergence (colour purity, RGB beam alignment etc) seems fine, just the ones for screen geometry (ie screen shape) like "pin" etc. You probably don't need to touch the yoke. Take a photo of the pots and post that if you want more commentary on this.

You could also take it up with the Facebook group "Sony PVM/BVM - Users of Sony Professional & Broadcast CRT Monitors". They might be more familiar with your gear. Again, pics are needed if you want responses.

Hi, thanks for answering...
Yeah, I tried when I made the post but for some reason it wasn't working.
Attached one Cross Hatch pattern.
Also

Notice the fatter Char Portrait/Flag on the right side. On photo seems minimal, but it's perceivable in game.

I guess I'm out of luck then... because this one isn't a PVM/BVM monitor. It's a regular PC, 31khz CRT. I don't think there are any "pots" in its chassis, even then, since it's only one side of the screen... Maybe I'm out of luck on this one. Convergence is all good indeed.

Anyway, thanks again!

Zebidee

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Re: Geometry/Deflection Yoke Fix Question
« Reply #3 on: August 19, 2018, 05:24:05 pm »
Worth notice that no matter what geometry settings (and there are a ton on this thing, including convergence) I fiddle up with, it won't help.
...
Quote
I guess I'm out of luck then... because this one isn't a PVM/BVM monitor. It's a regular PC, 31khz CRT. I don't think there are any "pots" in its chassis, even then, since it's only one side of the screen...

Ah, so you mean adjustments using some front panel thingy I guess.

PC VGA Sony (find that model number) who knows, regulars here more focused on arcade monitors. you could ask on the FB group they might know. There is also a "CRT collective" FB group. Many retrogamer members but many other types as well. Some VGA enthusiasts too, VGA looks better than LCD for retrogaming IMHO, esp for console emulators.

If you de-case the Sony you may (or may not) find some screen geometry pots worth adjusting, just make sure you know what you are doing first (safety first)  :police:  Mirrors also help  ;D
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buttersoft

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Re: Geometry/Deflection Yoke Fix Question
« Reply #4 on: August 19, 2018, 07:34:31 pm »
If there isn't a horizontal linearity option in the settings menu, a fix might be tricky. From the look of it, you've got a GDM-400 or -500 or newer, and those are digitally controlled. Recapping might help, but i doubt it.


Dacasks

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Re: Geometry/Deflection Yoke Fix Question
« Reply #5 on: August 20, 2018, 08:56:28 am »
If there isn't a horizontal linearity option in the settings menu, a fix might be tricky. From the look of it, you've got a GDM-400 or -500 or newer, and those are digitally controlled. Recapping might help, but i doubt it.

HORIZONTAL LINEARITY! that's the name of the thing. It already helped a lot, really... I'll dig into it and see what could be ruled. There's no adjustment on that, unfortunately... yes, it's a GDM 5410 (rebranded sun X7136A). Recap this thing probably I would try it down the road but really... I'm afraid only of opening it up right now because it weights a ton.

Playing fighting games on it is annoying as hell. But the screen is the largest PC CRT I ever got my eyes on. It's great, just put that arcade stick in front of it and BANG, almost like a third world poor man's candy cab or something (AND THAT'S MY CASE!).


Ah, so you mean adjustments using some front panel thingy I guess.

PC VGA Sony (find that model number) who knows, regulars here more focused on arcade monitors. you could ask on the FB group they might know. There is also a "CRT collective" FB group. Many retrogamer members but many other types as well. Some VGA enthusiasts too, VGA looks better than LCD for retrogaming IMHO, esp for console emulators.

If you de-case the Sony you may (or may not) find some screen geometry pots worth adjusting, just make sure you know what you are doing first (safety first)  :police:  Mirrors also help  ;D


Thanks man, unfortunately (or fortunately lolz) I don't have a facebook profile anymore... I DON'T HAVE FRIEND, ONLY BIG ASS MONITORZzzz kidding, but... I'll see. If I ever find something I'll come back here.

Dacasks

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Re: Geometry/Deflection Yoke Fix Question
« Reply #6 on: August 21, 2018, 11:58:50 am »
Found this
http://gradllc.com/IMAGES/LINEARITY.pdf

And found the Service Manual
https://elektrotanya.com/gdm-5410_sun_chassis_g1.pdf/download.html
T505 (pg 24) seems suspicious...

Really wished I had an old uncle now.

In any case, it's being very educational so far. Man, I gotta get into electronics "4real".