Adjustments in CRT

[Norco21]

sooo ive been reading on how to do this and i found out how but my CRT has 2 knobs for focus, horizontal and vertical, does it matter which one you do, or should u do one then the other, my monitor has gotten blurry over the years and thought id try this before i toss it lol, any info be great thanks, its a LG Flatron F900P monitor(FB910G-UL)

 

[stahlhart]

Welcome to the AnandTech forums -- I've moved your question to a more appropriate forum for its content.

I'd probably start with the focus and brightness adjustments first, then use the horizontal and vertical centering to make certain your screen has not drifted off of any of the outer edges.

There may also be convergence adjustments for the colors (purity), but I'd probably not mess with those unless you're really sure of what you are doing -- it's much easier to knock those out of alignment than to get them set correctly.

Edit: could a moderator here move this to Highly Technical, if they think that might be even more appropriate? I had second thoughts about this, but unfortunately my permissions don't allow me to move it now that it's out of VC&G...

 

[Ketchup]

sooo ive been reading on how to do this and i found out how but my CRT has 2 knobs for focus, horizontal and vertical, does it matter which one you do, or should u do one then the other, my monitor has gotten blurry over the years and thought id try this before i toss it lol, any info be great thanks, its a LG Flatron F900P monitor(FB910G-UL)

I would probably start on the OS side and take a look at the resolution and monitor refresh rate settings. I had a problem that sounds like what you are describing when I set either too high on my last CRT.

Don't rule out just doing a degauss either.

 

[Harvey]

Another welcome to our forums. Per stahlhart's note, I moved your thread to this forum. I also changed the thread title, which referred to the flyback transformer because, AFIK, flyback transformers in CRT monitors are not adjustable, and your own OP and any relevant answers have nothing to do with them.

First and foremost, BE VERY CAREFUL when working on an open CRT monitor. CRT's require very high voltage (25,000 volts or more) so be sure you know what not to touch, and keep all metal objects away from an open, powered CRT monitor. Also, after you power it down, stay away from it long enough for the voltage on the power capacitors to discharge. It could take a few hours. Don't try to discharge the caps with a tool such as a screwdriver. It could end up looking like a used welding rod.

To answer your question, it doesn't matter which you adjusts first. If they're interactive, you'll know as soon as you try to adjust them. Just take your time, and start with small adjustments until you get a feel for how sensitive the controls are.

If you can't bring the picture anywhere near good focus or horizontal or vertical centering, don't waste your time going any further. If your monitor is that old and in that bad a shape, the good news is, Best Buy and some other stores accepts old electronics for proper recycling.

If your monitor is old enough not to have a deguassing control, manually deguassing the CRT is probabaly the most effective thing you could try before doing anything else. You can do it with a motor driven hand tool such as a hand held electric hair dryer or an electric drill. When degaussing, you have to ramp the degaussing field up and down, not turn it on or off quickly.

1. Turn on the device AWAY FROM the CRT.

2. Bring it close to the screen and move it around the face of the CRT. If it's working, you should see moving color swirls following the movement of the tool.

3. Pull it away from the screen before turning it off.

There may also be convergence adjustments for the colors (purity), but I'd probably not mess with those unless you're really sure of what you are doing -- it's much easier to knock those out of alignment than to get them set correctly.

Convergence controls are not that difficult... as long as you take it slow and take note of where you start with them.

You can use NTSC color bars or any image with large blocks of primary colors red, green and blue, preferably against a white background. Look for "fringes" of each primary color at the edges of a block, and adjust each color to minimize those misaligned color edges.

If you really mess them up, as a fall back, you can always reset all of them to the center of their adjustment range and start over.

The real problem with all of these pots is if they become microphonic (subject to change with vibration) or they develop failing or intermittant wiper contacts due to age.

Hope that helps. Good luck.

 

[Norco21]

monitor is from 2003 so it is getting up there lol but if i can make is clear again still a decent monitor. settings in OS dont affect anything, and far as degaussing it its supposed to when u first turn it on and u can degauss it in the menu. but ill be giving it a go, also should i blow out all the dust in there cause its VERY dusty especially around the FBT.

 

[Harvey]

monitor is from 2003 so it is getting up there lol but if i can make is clear again still a decent monitor. settings in OS dont affect anything, and far as degaussing it its supposed to when u first turn it on and u can degauss it in the menu. but ill be giving it a go, also should i blow out all the dust in there cause its VERY dusty especially around the FBT.

OS (operating system) controls have nothing to do with this. If the horizontal, vertical, focus and convergence controls are not externally accessible, they are internal so please heed my previous warnings about high voltage shock hazard.

Yes, blowing out the dust is a good idea. Do this only when the monitor has been turned off for a few hours. Some of the flying partiulate could be conductive.

While you'e in there, look at all of the electrolytic capacitors. If any of them show evidence of leakage around the base, or if the tops of any of them are domed, the caps are bad. If so, that could cause the problems you're seeing, including competent labor, the cost of replacing them would be relatively expensive (versus the cost of a reasonable new flat screen), and there's no guarantee it would fix all of the problems because the failed caps could cause other component failures, as well. In other words, it would be recycling time.

FYI, ALL old style (non-solid) electrolytic caps age and fail, even those that don't show external evidence of it. I design pro audio electronics, and I'm suprised when I see good ones over 5-7 years old.

 

[Norco21]

i havent turned the monitor on in 6+ months, i know i can adjust the convergence through the OSD menu or you saying there is a physical adjustment aswell, main reason i was gonna attempt this is to use it at my shop for some office releated stuff but if someone ever broke in i wouldnt really care if they attempted to steal it as it weighs 61 lbs lol

 

[Harvey]

There may be internal adjustments, as well, to center the operating points of the color guns, but if the OSD adjustments work, use them. Same for the other controls if they're in the OSD.

 

[Norco21]

so im doing it right now and man its so sensitive turning it like a millimeter makes a huge diff but hard to do when your looking at the screen to lol, also on the FBT whats the screen knob do?

 

[Norco21]

well after like 30 mins of adjusting each knob id have to say its 10 times better than what it was, doesn't hurt my eyes trying to read text, knobs must of moved or something cause looks like its supposed to now, the screen knob has a dab of glue on it so not gonna bother trying to adjust that one

 

[Harvey]

:thumbsup:

If that dab of glue looks like it was done at the factory, it means that they didn't think you would have to adjust it. Skip moving it if you're satisied with how it is, now, However, any setting in a 10 year old CRT monitor could have drifted so you can try adjusting it. If you do, do it slowly and carefully until you get a feel for what it does.

And don't forget to feed the dust bunnies.

 

[bryanl]

It's safest to use a plastic or fiberglass tuning wand, both to prevent electrocution and to reach into small holes or crowded spaces. Radio and TV supply houses and ham radio shops sell them, or you can carve one from a stick.

Mark the original setting of each control, to make it easier to restore adjustments if needed.

Nokia has a monitor test that can generate patterns to help adjust focus and color convergence. Do not adjust color convergence except through front panel controls, not only because some adjustments are right next to high voltage (ring magnets around the CRT neck), but it's very difficult to get the convergence right.

 

[Matt1970]

It's safest to use a plastic or fiberglass tuning wand, both to prevent electrocution and to reach into small holes or crowded spaces. Radio and TV supply houses and ham radio shops sell them, or you can carve one from a stick.

Mark the original setting of each control, to make it easier to restore adjustments if needed.

Nokia has a monitor test that can generate patterns to help adjust focus and color convergence. Do not adjust color convergence except through front panel controls, not only because some adjustments are right next to high voltage (ring magnets around the CRT neck), but it's very difficult to get the convergence right.

I have adjusted the focus on many many monitors and want to double down on the importance of plastic or fiberglass tuning wand. That red wire coming out the the flyback transformer (where the focus adjustment is) is the big one to avoid. Touching that red wire with a heart condition can kill you. I have been but a few times and it hurts, a lot. The flyback generates right at 30,000 volts and it carried to the tube via that wire. The current will typically jump right therough the insulation on the wire which is why they have a plastic ring to keep it from touching anything. If you have ever felt the zap from the front of a TV set, that is the same voltage just less amperage.

My honest recommendation is to look on craigslist. People are giving those things away as it costs $10 a piece to dispose of them.