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Does a CRT lose its ability to focus as it gets older?

F

Felecha

Golden Member
Samsung SyncMaster 1100p Plus, 21", it was such a splurge to get it almost 6 years ago. HUGE screen, and it has worked just fine all along, except some time recently, maybe over the last 6 months or so, it has become fuzzy around the corners of details. There was no sudden event, no day when I looked and said "Wow, what happened??" I can't even remember how long it's been happening.

I run it at 1280x1024, and have the fonts as small as I can read them, I am a programmer and like to get as much showing as I can. In windows Explorer it's got to the point where if I didn't already know the folder names and the name were something like "Greddhog" I might look closely to see if it was an e or an o.

The odd thing is that at random times I find it much sharper, as if some focus capability has snapped back in place. Then over 5 or 10 minutes it will fuzz out again. It only happens when I come in and wiggle the mouse to wake it up. So somehow coming out of blank sleep, it is cleared, but not for long. I have not found that turning it off and back on will bring it into sharpness.

I discovered just the other day that the monitor controls include a Focus (!!!) and I played with that but it seems like the horizontal and vertical values from 0 to 100 just move some kind of center of focus across the screen. At 0 on horizontal, the left side is pretty good, and the right side is really actually unreadable. And 100 is the opposite. And yes, somewhere around 50 for each is about the best overall, so it seems like whatever the focusing mechanism it just moves it up and down or sideways.

Anyway, the question is - is this something that CRT's in general are susceptible to with age?

Thanks
 
Having no idea what that means I did already try that a few times and yes it's fun, but did not seem to have any effect.

And here I am having returned to my computer after being out, hit the mouse, things are much sharper right now. I wish I knew how to reproduce whatever happens when this happens so any time I want to I could just do something and make the focus sharper. Manually shutting the monitor off and back on does not seem to do it
 
The High Voltage Stage in the CRT may be wearing out I have a 21" Hitachi this happend to and the screen did what you describe for awhile and then just stayed blurry, unforunatly its not worth fixing as you can buy a new 20" + lcd for what it would cost to have fixed.
 
Yes, crt displays can lose Focus .. if you open it up, on the Flyback (the unit with the
heavy Red wire that goes to the neck of the crt) you will usually see a small knob
marked "Focus" .. on some units it can be accessed thru a hole in the case cover
Turn it for best results ... if you can not get it acceptable, then it is a circuit problem
or the CRT itself is starting to go bad

Note: If you open it up, be very carefull .. use insulated screwdrivers only
and do not touch any parts with unit Plugged In or Powered On
These units have voltages of many levels, ranging from +5V to 30KVDC
in addition to normal 110VAC .. anyone of which can be very painfull / deadly
 
No access holes that I can see, and I dont like pain or death, so I will let that idea lie like a sleeping dog. Part of the question came an idea that if this one is on the way out my family could chip for a christmas present, like a 20" lcd. Very attractive idea, indeed, but seems a waste if there is actually a reasonable fix. When this one is in a clear moment, there is no reason at all to go for anything new.

Thanks all
 
Interesting, I just played around, neverr thought of this before. I went into Desktop | Properties |Screensaver and the Monitor Power setting, since both would happen if I went away for a while. Turns out that doing the Screensaver Preview thing will restore a good focus, but not for long, I can watch it fuzz out. The longer I leave it in the preview state the longer it takes to fuzz. If I've been away a while, so presumably the screensaver state has had a good long time, I know it can take minutes to go fuzzy. So it looks like something is indeed weak in the knees back there, and the screensaver lets it get a rest -- cool down or something.

In any case, it looks likely to be a no-fix, like ArcaneDeath suggested. Oh well ...

 
CRTs have a DC focus voltage applied to the yoke. It has to be a stable voltage, so there are one or more capacitors to take noise off the line. A "leaky" capacitor (electrically "leaky", not physically leaking, since these are typically ceramic disc capacitors rather than electrolytic or tantalum) can cause this voltage to vary, and thereby screw up the monitor focus. A competant technician can fix this, but it won't be cheap.
 
Glasses - yes, that COULD be a factor, but I've tested for it and eliminated it.

CallYouJoe - yeah, the Christmas idea is looking good

Thanks all

F
 
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