Convergence

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Convergence

Postby SpidersWeb on Sat Jan 26, 2013 2:53 pm

Anyone here had to fix convergence issues in CRT's before?

Will there be an adjustment inside the case?

Blue and Green are tolerable, but red is like 2 pixels off, it confuses my brain when using it.
Monitor is an IBM VGA (PS/2 era), it's been like this since I got it.
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Re: Convergence

Postby Gibsaw on Sat Jan 26, 2013 6:06 pm

nah... "untested" or "have no way to test", and price it at $500... then get REALLY bolshy when people start to suggest you might be hiding something after not answering reasonable technical questions with clear instructions.
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Re: Convergence

Postby Gibsaw on Sat Jan 26, 2013 8:37 pm

Yes, there should be adjustments internally, but you'd probably need to find a schematic. May not be clearly labeled.
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Re: Convergence

Postby cjr on Sat Jan 26, 2013 11:59 pm

unless it's a fairly new device, it's probably an analog adjustment. if it's digital, then sorry I don't know.
if analog.. there ought to be 3 pairs of magnetic rings around the neck of the tube, one pair for each colour.. twiddle away but maybe mark their position before beginning.. :) they all influence each other so you can end up fiddling for a while. There maybe a clamp holding them in place that you should loosen a little first.
they normally look like this; http://forum.arcadeotaku.com/download/file.php?id=1023&sid=17bb996adfc68c42467a7e8859efeec1&mode=view
a quick google turned this up, some good tips. https://www.youtube.com/watch?v=eDuKddayX-E - be safe.
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Re: Convergence

Postby Gibsaw on Sun Jan 27, 2013 9:12 am

Yes... be very careful... Very high voltages that are still present even when the device is unplugged.

EDIT: After a quick search, pays to discharge first using the proper HT meter, or for a more "yee-haa, ride 'em cowboy" approach, you could try this approach using a screwdriver.
Last edited by Gibsaw on Sun Jan 27, 2013 11:13 am, edited 3 times in total.
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Re: Convergence

Postby SpidersWeb on Sun Jan 27, 2013 9:29 am

LOL @ earlier posts, even my girlfriend got a good laugh from those.

Thanks cjr, I'd say that's probably it. I'm not game enough to go inside a monitor with power applied - so I may just ignore it for now. I was hoping for some cute little potentiometer I could get with an insulated screw driver. Very handy information to know though if I find a rarer screen that needs a small adjustment.

I was using it for a few hours yesterday and remembered it has bad screen burn - so perhaps I'll just make it a spare and look for a replacement at some stage. I am about to leave and pick up another complete PS/2 - hopefully it's screen is perfect.
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Re: Convergence

Postby falco on Sun Jan 27, 2013 9:51 am

One thing I have to admit I'm curious about - if it's magnetic convergence (like practically all monitors really), how has it ended up with bad convergence? I assume it's bad all over the screen to the same extent? It's kinda weird. As you can see in the picture, these are supposed to have a blob of glue on them from the factory so they can't move. It's all relative - if the rings, the guns, the shadow mask, and the phosphor haven't moved, it should be very reliable. If any of those have moved apart from the rings, you have bigger problems anyway, but that's hardly likely given the symptom.

Thought - have you opened it up and made sure the magnetic ring assembly hasn't come loose on the tube neck? I have seen them where the rings are all still glued to each other, but the clip that holds them all in place has come loose and they're floating around. That's pretty easy to put back. The clip I'm talking about is the one in the picture nearest the tube base board.
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Re: Convergence

Postby cjr on Sun Jan 27, 2013 9:31 pm

SpidersWeb wrote:I'm not game enough to go inside a monitor with power applied - so I may just ignore it for now.

And because you need to see what's happening with the alignment, leaving it on is kind of a requirement. :)
If you want, I could look at it sometime.. I'm not afraid - had plenty of years servicing TV's way back when.
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Re: Convergence

Postby SpidersWeb on Mon Jan 28, 2013 7:41 am

I have a replacement PS/2 screen now that works 100% (I was waiting for a bang, but it worked perfectly).

I'm moving house next weekend, and have a lot of other projects which should be taking priority, so I may not get it open for quite a while to look at the rings. Because of the bad screen burn I'm just calling it a 'spare/backup/parts' - but if you were curious about what's happened with the rings you'd be welcome to have a look cjr.

I'm guessing either there is a partially electronic adjustment which has gone awry, or somebody gave it a big knock at some stage. It has CGHS written on it in vivid - which I guess is a high school - so might not have had the easiest life! It was also posted to me, so maybe that did it.

99% it's ok, just a bit sore on the eyes in text mode, in the RAM test you can clearly see solid red pixels next to the white text. Don't really notice in games or a GUI.
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Re: Convergence

Postby SpidersWeb on Mon Jan 28, 2013 7:50 am

falco wrote:One thing I have to admit I'm curious about - if it's magnetic convergence (like practically all monitors really), how has it ended up with bad convergence? I assume it's bad all over the screen to the same extent? It's kinda weird. As you can see in the picture, these are supposed to have a blob of glue on them from the factory so they can't move. It's all relative - if the rings, the guns, the shadow mask, and the phosphor haven't moved, it should be very reliable. If any of those have moved apart from the rings, you have bigger problems anyway, but that's hardly likely given the symptom.

Thought - have you opened it up and made sure the magnetic ring assembly hasn't come loose on the tube neck? I have seen them where the rings are all still glued to each other, but the clip that holds them all in place has come loose and they're floating around. That's pretty easy to put back. The clip I'm talking about is the one in the picture nearest the tube base board.


Haven't opened her up yet. May play with it at a later date. I remembered the screen burn after I'd posted this, somewhat put me off making time for it - next on my project list is actually trying to start my Model 30 with my Model 56 PSU.

I believe it's worse in the top left corner, but to confirm I should really put a test pattern on the screen. Once you're in a game or GUI you barely notice, just white on black text - which still looks white but hurts the eyes - then you look closer and see solid red pixels 1 up and 1 left of where they should be.
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Re: Convergence

Postby falco on Mon Jan 28, 2013 8:29 am

True, phosphor burn is pretty fatal as far as I'm concerned, I'd use a monitor like that as a spare if at all. Well, if you do find out what the story is at some stage, I'd be curious to hear...
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