What picture flaws to look for when buying used CRT TV?

[Brad251]

I bought a used Sony kv-24fs100 CRT TV off of Craigslist recently and will not be keeping it because the blacks on the TV are very crushed and greys barely show up at all. I have gone through every option in menu and service menu to try to correct for this and nothing works. I even adjusted the screen knob.

I am looking to get another used CRT TV and was wondering what major flaws in the picture I should be checking for before buying another CRT? I do have an Avia calibration DVD. What aspects of the picture can be corrected and which ones can't be corrected through the service menu? If there is a problem with convergence, is it really that hard to adjust the magnets inside the CRT to fix that aspect of the picture?

[accaris]

I bought a used Sony kv-24fs100 CRT TV off of Craigslist recently and will not be keeping it because the blacks on the TV are very crushed and greys barely show up at all. I have gone through every option in menu and service menu to try to correct for this and nothing works. I even adjusted the screen knob.

I am looking to get another used CRT TV and was wondering what major flaws in the picture I should be checking for before buying another CRT? I do have an Avia calibration DVD. What aspects of the picture can be corrected and which ones can't be corrected through the service menu? If there is a problem with convergence, is it really that hard to adjust the magnets inside the CRT to fix that aspect of the picture?

Gamma setting in the Sony service menu didn't help the black levels? From what I recall it goes from 0 to 3. But on the other hand, 24FS100 is a very low-end Trinitron. Like, bottom of the barrel in terms of quality.

There are several issues which cannot be adjusted in any service menu, and you're right in guessing that convergence is one of them. I personally wouldn't waste a lot of time trying to adjust convergence manually with magnets in a consumer-grade CRT, unless it's a rare or high-end one. But it can be done with a lot of trial and error.

The most noticeable issue which can't be adjusted in the service menu is picture rotation. Eventually the beams on most CRTs will fall out of alignment due to gravity. Many Trinitrons have a service menu setting that can correct rotation (called TROT,) but if it's any other brand, including Panasonic, Samsung, JVC, or Toshiba, you're shit out of luck and you'll have to open up the back of the tube to fix it by loosening the screw on the neck and adjusting the deflection yolk. This can be a time consuming and FRUSTRATING process. (Just when you think you have it perfect, you'll put the rear cover back on the TV, turn it on, and it'll be off! Arrgggh)

Horizontal bowing is also something you'll have to open up the tube to fix. No service menu setting will fix horizontal bowing, regardless of brand. You'll have to manually adjust the yolk angle and while you're doing this, you'll probably screw something else up, like the rotation. Get ready for an hour or more of messing around next to deadly voltages.

Phosphor burn-out. You can usually see this as a darkened area of the screen, especially on solid backgrounds. On white backgrounds it can appear yellowed or brown. Now, this *could* be a purity issue resulting from the deflection yolk being too close to the screen, but most of the time it means the set has degraded due to overdriven brightness or contrast and nothing you can do will save it.

Magnetization. Manifests as a purple, green, or blue color splotch in a corner(s) of the screen. Caused by having the tube too close to a magnetic source, but it can also be caused just by age and exposure to the earth's magnetic field. A degaussing wand can sometimes fix this, but if it's been that way for too long, the damage will be permanent.

Horizontal overcscan. Most Trinitrons have horizontal adjustment settings (HSIZ, TRAP) but many other brands do not. Any size smaller than 27" will probably be missing the circuitry for horizontal adjustment, even if the setting itself is still present in the firmware. This was the case with a 2004 Samsung DynaFlat I bought recently, for example. If the TV is cutting off space on the left and right edge of the screen, you might be out of luck trying to fix it in the service menu. Luckily, for some reason vertical adjustment settings are much more common and universal.

Blurry corners. I've only ever seen this phenomenon on JVC curved tubes from the 2000s, which is a shame because those usually have AMAZING geometry. There is a focus pot on the flyback transformer that can normally fix most blurry screen issues, but for some reason, if the center is sharp and all four corners are blurry, the focus pot did absolutely nothing to fix this on that JVC. Usually you can make the center of the screen sharp, OR the corners sharp, but not both at the same time.

[mvsfan]

the main thing i would check for on a sony is any purple spots on the picture. sometimes they can be taken out with a degaussing wand

but it may indicate that your aperature grill has come loose and theres no fix for that.

most other issues can be adjusted out using the service menu.

[Brad251]

Blurry corners. I've only ever seen this phenomenon on JVC curved tubes from the 2000s, which is a shame because those usually have AMAZING geometry. There is a focus pot on the flyback transformer that can normally fix most blurry screen issues, but for some reason, if the center is sharp and all four corners are blurry, the focus pot did absolutely nothing to fix this on that JVC. Usually you can make the center of the screen sharp, OR the corners sharp, but not both at the same time.

If you can't use the focus pot on one of these 2000s era JVC crts to fix blurry corners, is there anything else that can be done to fix the blurry corners on these TVs?

[accaris]

Blurry corners. I've only ever seen this phenomenon on JVC curved tubes from the 2000s, which is a shame because those usually have AMAZING geometry. There is a focus pot on the flyback transformer that can normally fix most blurry screen issues, but for some reason, if the center is sharp and all four corners are blurry, the focus pot did absolutely nothing to fix this on that JVC. Usually you can make the center of the screen sharp, OR the corners sharp, but not both at the same time.

If you can't use the focus pot on one of these 2000s era JVC crts to fix blurry corners, is there anything else that can be done to fix the blurry corners on these TVs?

I did as much research as I could when I was trying to fix this and no, I simply couldn't find a way around it.

[Brad251]

I appreciate your help, Accaris.