My CRTs have excessive brightness

[CRTguy]

I have two CRTs, a Toshiba CF27F30 from '96 and a JVC AV-2672S from '93. On the Toshiba set, it is only with brighter colors (particularly red, brown, green and yellow) that the brightness is excessive to the point that it hurts my eyes. I can somewhat compensate for this by turning down the contrast a lot but then the black levels really suffer and shadow detail is poor. I have used test patterns to calibrate both sets. So far, on the Toshiba set, I have replaced all of the electrolytic capacitors as well as the flyback and it hasn't helped. I have also reflowed solder to all pads on the neckboard and tested the transistors, diodes and large resistors with my DMM on the neckboard on the Toshiba set. I still have to get around to testing the small resistors on the neckboard.

My JVC set also has excessive brightness with brighter colors but it is with all colors and not just red, brown and yellow. I actually had to open the JVC set up and turn down the contrast pot on the main board to even get the picture to be somewhat tolerable without hurting my eyes a lot.

I have also experienced this excessive brightness issue on almost every CRT TV I have picked up that was made before the year 2000 (90s JVC sets I picked up were particularly bad). What could be causing this? It seems like there is more going on than just bad electrolytic capacitors. Can a shorted tube cause brightness problems like the one I am describing? Maybe it is a bad transistor, resistor or diode?

[zeno]

On both sets check:
1) the G-2 is not too high. Should be apx 450 VDC. at CRT pin
2) on the CRT board there are 3 identical resistors ( apx 18K 2 watt)
Where they join be sure you have apx 200 VDC.
3) if you turn down the bright, contrast & color level you should be able to extinguish or nearly so the pix. Turning back up the brite & contrast should
show a constant B&W pix as you go up. If it changes color as you go it may
be the CRT.

good luck.
73 Zeno
LFOD !

[old_tv_nut]

"The colors hurt my eyes" is more a description of you than of the set.
Please be more specific about the set itself.
When you turn the contrast down "the black level suffers." Do you mean the blacks are too dark, or too bright?
Certain colors bother you. Does the picture look too bright or too dark or have an over-all tint when you turn the color all the way down and view in black and white? Can you get a pleasing result for the problem colors by turning down the color control? Are other colors then too muted?

[CRTguy]

Originally Posted by old_tv_nut

"The colors hurt my eyes" is more a description of you than of the set.
Please be more specific about the set itself.
When you turn the contrast down "the black level suffers." Do you mean the blacks are too dark, or too bright?
Certain colors bother you. Does the picture look too bright or too dark or have an over-all tint when you turn the color all the way down and view in black and white? Can you get a pleasing result for the problem colors by turning down the color control? Are other colors then too muted?

When I turn the contrast down, blacks are too dark. The picture doesn't have an overall tint of one particular color but it is too bright. Specifically, only the brighter colors involving red, green, brown and yellow are too bright. In order for the picture to not hurt my eyes, I have to turn down the color control and contrast so much that the picture then looks dull. I do sort of have a point of reference for the Toshiba set as I used to own the same model of Toshiba set before. The previous CF27F30 model that I owned before had a more worn out tube as there was a slight yellowish tint to the picture. However, on that previous model that I owned, the colors were not too bright and the picture didn't hurt my eyes at all. The brightness was perfectly balanced.

As for my JVC CRT, I suspect that something is wrong because before I even opened the set up to do any adjustments, the picture was still way to bright, even when I turned the contrast down to zero. I had to open the set up and turn the contrast pot down on the main board.

[CRTguy]

Originally Posted by zeno

On both sets check:
1) the G-2 is not too high. Should be apx 450 VDC. at CRT pin
2) on the CRT board there are 3 identical resistors ( apx 18K 2 watt)
Where they join be sure you have apx 200 VDC.
3) if you turn down the bright, contrast & color level you should be able to extinguish or nearly so the pix. Turning back up the brite & contrast should
show a constant B&W pix as you go up. If it changes color as you go it may
be the CRT.

good luck.
73 Zeno
LFOD !

Hi, Zeno, I don't have any high voltage testing equipment. What would be the cheapest options that you would recommend? I was thinking of getting a fluke meter and a fluke meter high voltage probe.

Is the pin labeled G2 the CRT pin?

When you say "pix', do you mean picture? When turning the brightness, contrast and color all the way down and then back up, are you saying that I should notice a consistent level of change in brightness without any brightness spikes?

[maxhifi]

Are you trying to watch TV up close in a fully dark room? The average CRT television was designed to be watched in a room with normal ambient lighting, and from a distance.

If you want to "make it less bright", you will need to turn down the brightness, and then adjust contrast to make the picture look good. These two controls have some interaction, so it may take some fiddling to get it right. If the color is too strong, then turn the color down too.

TVs were always set by default to maximum brightness and contrast, to stand out in stores. I always dial mine down to reduce the wear and tear on the CRT, and to make the picture look better.

Am I getting the impression you didn't grow up with CRT televisions? These controls are all second nature to those who did, but I could see them being confusing to those who didn't. I suggest to just keep playing with them until the picture looks good. One tip is to turn the color down all the way to get a monochrome picture, and then set the contrast and brightness. Once you have done this, slowly increase the color until it looks realistic. You will find it will be set WAY lower than the over saturated look which most TVs have.

Also, don't expect digital quality black levels with an old TV. Black is always going to be a little murky, it's better to not obsess over it.

[CRTguy]

Originally Posted by maxhifi

Are you trying to watch TV up close in a fully dark room? The average CRT television was designed to be watched in a room with normal ambient lighting, and from a distance.

If you want to "make it less bright", you will need to turn down the brightness, and then adjust contrast to make the picture look good. These two controls have some interaction, so it may take some fiddling to get it right. If the color is too strong, then turn the color down too.

TVs were always set by default to maximum brightness and contrast, to stand out in stores. I always dial mine down to reduce the wear and tear on the CRT, and to make the picture look better.

Am I getting the impression you didn't grow up with CRT televisions? These controls are all second nature to those who did, but I could see them being confusing to those who didn't. I suggest to just keep playing with them until the picture looks good. One tip is to turn the color down all the way to get a monochrome picture, and then set the contrast and brightness. Once you have done this, slowly increase the color until it looks realistic. You will find it will be set WAY lower than the over saturated look which most TVs have.

Also, don't expect digital quality black levels with an old TV. Black is always going to be a little murky, it's better to not obsess over it.

I am well versed in CRT/TV calibration. I grew up with CRTs and used only CRTs for the first 23 years of my life; I'm 35. I'm very familiar with what each picture control does, proper calibration techniques, and what a balanced image looks like on a properly functioning CRT. I use an app for the Nintendo Wii called Artemio's 240p Suite that has all kinds of test patterns for adjusting contrast, brightness, color, tint, screen geometry, etc. I watch my CRTs in a medium lit room and I have calibrated all of the picture settings using the test patterns and I have used this process on dozens of CRTs. I have also experimented with turning down the screen (G2) knob on the flyback transformer but it didn't make a difference. I also use blue gel filter glasses for calibrating color and tint.

So, I've done all of the calibration that I can possibly do and I suspect that there is something going on in my sets that is causing the voltage to be higher than it should be which is causing the brighter colors to be brighter than they should be. I do know that this can be caused by things such as bad components on the neckboard such as a bad transistor, diode, resistor or possible even a short in the tube itself or a bad flyback.

[old_tv_nut]

It's hard to believe that a set can pass the blue filter calibration and still have something malfunctioning.

You should know that all analog NTSC sets with modern green phosphors have an increased R-Y gain built in to compensate the yellowness of the green phosphor. What this does is decrease the amount of red in greenish colors to make up for the equivalent amount of red that is added by the yellowish green. Unfortunately, it also works the other way and over-brightens pure reds, due to the non-linear "gamma" of the picture tube. Calibrating with the blue filter gets the B-Y signal to a standard level, leaving the R-Y with this increase. This problem was solved in PAL and HDTV by doing the correct compensation for the green phosphor at a linear signal point in the camera.

In your one set that has very unbalanced drive in the reddish colors vs. others, you may have a bad color chip or some failure in the color demodulator circuit.