Alternative Way of Adjusting G2s (25EC58)

[vol.2]

Originally Posted by TinCanAlley

I did notice something when doing the G2s. I turned them all down, but the grayscale pattern I had up was tinted green. Is that supposed to happen?

Yes, this is completely normal and every TV will show one color stronger than the other two with the controls turned all the way down.

This is just a reflection of the strength of the guns and is exactly why there are adjustments there by design. The whole system changes as it gets used and over time, so it's never going to be perfect out of the gate.

You want to leave the green G2 down almost to the very minimum and just correct with the red and blue to make the darkest grey look a pure grey.

In theory, you can leave the green down all the way, but I usually will turn up the brightest color a tiny bit because I don't like to operate a potentiometer at its extreme. Especially those older pots can have damage or weak spots on the ends sometimes. It can also be beneficial to have a tiny buffer in case you want to correct for it while balancing.

The dark room mostly helps you to see the color at low light better, where the G2 controls are going to be doing their work.

I used to do it by eye, but I can't really anymore; my night vision is pretty bad at this point. I purchased a used color meter on ebay and that works quite well.

[TinCanAlley]

Okay, when I redo the G2s, I'll bump up the green slightly from the fully counter clockwise position and move up the red for yellow, then blue for grey.

I guess heat over time in the convergence pots lead to one losing part of it's shaft. It broke outside of the pot, so it is still adjustable with a plastic screwdriver. The shaft is purple, but where it broke is brown and I'm assuming the heat got to it. I have a new pot, but I don't think it will be necessary to install. I have avoided changing any pots that don't test bad as they are three legs in the solder buckets. I have no way of heating up three pots at once, let alone get them hot enough to all melt so I can pull the legs out. I was think one by one, but the needle nose will just act as a heat sink. Then there's the issue of installing the new one. Those buckets aren't so bad individually, but when multiple ones are involved, they're a nightmare.

I have 5 out of the 9 pots and already installed new coils. The 4 I don't have are pretty hard to locate.

[TinCanAlley]

Well I did the G2s over again. I increased the green until I saw a slight increase in intensity and then added in the other guns to get the best grayscale I could with my eyes. However, when I tried to set the contrast and brightness, I had to go full on the brightness in order to get a decent picture. I figured that if this was full brightness, I needed to go higher on the G2s, so I started over and this time brought the green up a little more than last time. Again, it needed just about full on the brightness control. Third time is a charm? I did it again and put the green up even more, somewhere just shy of 50% on the control. After adding in the other guns for the grayscale, I was able to get the brightness level with a little to spare. According to the CRT tester, all guns are good and very close to each other, so I don't think it's the CRT. Maybe something in the aging electronics.

Anyway, now I just need to replace the broken pot on the convergence board to finish it up. I am kicking myself for even touching it as I was pretty darn close to perfect with the only misalignments on the far corner and a bit on the right edge. Oh well, that'll teach me.

[vol.2]

Originally Posted by TinCanAlley

According to the CRT tester, all guns are good and very close to each other, so I don't think it's the CRT. Maybe something in the aging electronics.

I think it actually has to do with the way our eyes perceive different colors.

The human eye is far more responsive to greenish colors, so if all the gun intensities are equal, then you would see more green.
https://en.wikipedia.org/wiki/Color_...ensitivity.svg

[TinCanAlley]

I think I need to put the set away for a while before I start to lose my mind. Upon turning it on this morning, the jailbars that are usually barely visible now have color tint along the left sides of the far left ones. This goes away after about 5 minutes, but it has to be a warning that something is about to go even more wrong. While the set has been recapped, it is possible that one or more are not doing so well. It has been about 13 years and a cap or two could be failing or out of spec.