Alternative Way of Adjusting G2s (25EC58)

[vol.2]

Originally Posted by TinCanAlley

I think I'll check the single capacitor on it and then install it.

You might want to do a quick check on the resistors while you are at it.

Generally speaking, the resistors should be their value or lower when in circuit because any additional paths that they might follow in parallel to their position in the circuit will only bring the total resistance down, not up.

So if you check a resistor and it is either open or it's resistance is higher than the value on the case, you should remove one leg from the circuit and give it a real test.

It's also a good idea to (if possible) identify places in the circuit where there should be ground (zero volts) and a power rail, and make sure those places are not a short.

[TinCanAlley]

Originally Posted by vol.2

You might want to do a quick check on the resistors while you are at it.

Generally speaking, the resistors should be their value or lower when in circuit because any additional paths that they might follow in parallel to their position in the circuit will only bring the total resistance down, not up.

So if you check a resistor and it is either open or it's resistance is higher than the value on the case, you should remove one leg from the circuit and give it a real test.

It's also a good idea to (if possible) identify places in the circuit where there should be ground (zero volts) and a power rail, and make sure those places are not a short.

I can do that.

Any idea which board could alter tint? I see it on the schematic at the subcarrier and going to the chroma. Is it the subcarrier altering or is the chroma also able to alter it if something is wrong on the board?

I think I'm also going to pull each board, deoxit all the contacts on chassis and boards. I also noticed that when I look at pics of the chassis when I first got it, each board had 2 blue tubes on unused pins. No doubt used to secure the boards, but are these a real necessity or more for shipping? I really can't remember where I put them as I didn't put them back on the modules.

[vol.2]

Originally Posted by TinCanAlley

I can do that.

Any idea which board could alter tint? I see it on the schematic at the subcarrier and going to the chroma. Is it the subcarrier altering or is the chroma also able to alter it if something is wrong on the board?

I think I'm also going to pull each board, deoxit all the contacts on chassis and boards. I also noticed that when I look at pics of the chassis when I first got it, each board had 2 blue tubes on unused pins. No doubt used to secure the boards, but are these a real necessity or more for shipping? I really can't remember where I put them as I didn't put them back on the modules.

Again, I'm not really that familiar with these sets to the point I can offer a lot of specific advice on them.

Someone else will have to comment on which board does what.

I definitely agree with the idea of cleaning board edge contacts though. That can solve a lot of problems.

A related thing to check is the solder joints on any connectors that get stress. If you have edge contacts that slide into connectors, those connectors will be prone to cracked solder joints, and that is a common cause of intermittent issues because they can make good contact until they heat up, and then the heat causes things to warp and push apart and issues start to show up.

It's not a slam-dunk, but it is a common kind of fault and worth just reflowing.

If I'm working on an old set (regardless of the make), I will generally do three things before I bother even turning on. I check and replace any bad electrolytics, I use contact cleaner and fader lube on every contact, switch, pot, fader, jack on the set, and I reflow every single connector, socket or large heavy component (like a transformer) on the PCB.

My time is too valuable to chase my tail over a cracked solder joint if you know what I mean.

[TinCanAlley]

Originally Posted by vol.2

Again, I'm not really that familiar with these sets to the point I can offer a lot of specific advice on them.

Someone else will have to comment on which board does what.

I definitely agree with the idea of cleaning board edge contacts though. That can solve a lot of problems.

A related thing to check is the solder joints on any connectors that get stress. If you have edge contacts that slide into connectors, those connectors will be prone to cracked solder joints, and that is a common cause of intermittent issues because they can make good contact until they heat up, and then the heat causes things to warp and push apart and issues start to show up.

It's not a slam-dunk, but it is a common kind of fault and worth just reflowing.

If I'm working on an old set (regardless of the make), I will generally do three things before I bother even turning on. I check and replace any bad electrolytics, I use contact cleaner and fader lube on every contact, switch, pot, fader, jack on the set, and I reflow every single connector, socket or large heavy component (like a transformer) on the PCB.

My time is too valuable to chase my tail over a cracked solder joint if you know what I mean.

I'm going to remove all the boards and clean all contacts and reseat. Will also check all components on the boards that handle color. The schematics show the tint control connected to the subcarrier, but if the correct setting hits that board and is then sent to the chroma board, it could change if that board has issues.

[TinCanAlley]

Been awhile since I posted an update and possible question or two.

I managed to get my hands on a new IC for the chroma board and just got some 16pin sockets. I'm going to remove the individual pin sockets on the board and replace with a single unit and put the new IC in. I'm leaning toward all my tint issues being this board. The tint is done by the subcarrier by changing the phase of the burst which then goes to the chroma board. At first I thought the subcarrier, but now I get sudden burst of fully saturated color as if I turned up the color control to max. It can last anywhere from 1 second to almost a minute. Yesterday during a couple of hours of viewing, it did it 9 times and the tint wandered a bit, but nothing extremely noticeable. Since the burst with tint phase hits that board, and the color is done on that board, it is most likely on that board. The IC handles both of those, so if it's faulty, changing it is my next step in troubleshooting.

And of course I have a question. I've noticed recently that on images with red or orange, there is a ghosting of that color to the left of the image. For instance, a person was wearing red suspenders and to the left of the suspenders, there was a lighter transparent red on his shirt leading to the suspenders. I also noticed the same with someone wearing orange. No other color does this. Might by related to the issues I'm having with tint and color saturation. All searches I've come up with point to a capacitor, but I've replaced all the electrolytics. Guess one could be bad already.

If you want an pic, I can take one and post it.

[TinCanAlley]

Finished modifying and installing the new IC on the Chroma board. Will have to run it through its paces and see if it helps. I think it already has as the tint was off from how it was before the new IC and it adjusted as expected.

[TinCanAlley]

More than 4 hours of testing the new IC and socket and all is well. No tint shifting or color going full saturation. It seem I found the culprit and now can focus on enjoying the set.

I hooked up the Archer Video Distribution System with a VCR, Laserdisc and DVD player connected to it. Each on get switched from their standard channel 3 to separate channels on UHF, so now I can just fire up a device or more and switch the channel to view it. Kind of cool device. Just wish I could get them to broadcast for wireless viewing.

[TinCanAlley]

Well I've just remembered another issue I notice some time back, but didn't address it as I hadn't completed all the hardware repairs. Now that those seem to be done, I'm going after this one.

When adjusting brightness and contrast, the grays are more green than gray. The whites are perfect, so I'm not sure where the green is coming into play. Maybe I didn't adjust the G2s properly? I have to adjust them using a B&W image as the setup switch won't bring up the lines as noted in the SM. What I did was turn them completely down and then turn on until I saw the color in the image. I then did the next until I noticed the color blending with the last one. The finish one I turned up until it looked like a B&W image. After that I adjusted the taps to remove color from the white areas.

The attached pic is a bit greener in than what I was seeing. I tested the CRT a couple of times and it tests good on all guns.

So how can the whites be so white while the grays are greenish? If it were a color gun imbalance, wouldn't it affect the whites?

[TinCanAlley]

Never mind, figured it out. I backed the G2 for green off until the grayscale pattern looked as good as I could get it. Then backed the red off just a tad and now it looks great. I tested it with going full brightness as that seems to highlight the color that's up too high.

Plus side, the issue with blacks in dim scenes is much improved and the transition between scenes no long displays a dim greenish gray screen and seems to stay pretty much black. Guess many of my issues, beyond hardware, is user error.

[vol.2]

Originally Posted by TinCanAlley

Never mind, figured it out. I backed the G2 for green off until the grayscale pattern looked as good as I could get it. Then backed the red off just a tad and now it looks great. I tested it with going full brightness as that seems to highlight the color that's up too high.

Bias/Background are going to primarily effect the low light color balance.

Drive is going to primarily effect the high light color balance.

There is absolutely interactivity between the two, but each is designed to have a greater effect on the color balance at their own brightness levels.

You want to correct for the low light color balance with the Bias/Background controls and correct for the brightest white color balance with the Drive controls.

However, because there is interactivity, you have to go back and forth between the two. Correct the grey at 20 IRE (fairly dark grey) with the Background controls, then display 100 IRE white (brightest white) and color correct with the Drive controls. Each correction will knock the other one out a little bit. The goal is to go back and forth until you reach the point where they are as even as possible from darkest to brightest.

So when you said this "I tested it with going full brightness as that seems to highlight the color that's up too high."

You don't want to turn up the brightness until you get a white raster and then try to color balance with the background controls. If that's what you are doing.

The idea is to be in a completely pitch black room and just barely turn the brightness up so you can see a dark grey raster, and then make that as perfect as you can get it with the backgrounds, without turning up the brightness. Then you switch to bright white and do the Drives, switch back, rinse repeat.

This often involves covering windows with cardboard or blankets to get the room dark enough and using flashlights to locate adjustment pots.

[TinCanAlley]

I did it in a dim room, but will do again at night to get it pitch black.

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? The green was pretty dark and when raising the green G2, it got a brighter green. Once I got that, I brought up the red til it was pretty much yellow and then the blue til it looked like a grayscale. I went back and forth with them until I saw no colors in the gray areas. From there I took the red tap from Hi to Med and the whites lost the red tint. So now the white are white and the grays are gray.

I find that when I adjust the controls according to the calibration DVD, it is too dim for normal viewing, so I adjust by eye from there. The DVD worked on a Toshiba 50" projection back in 2000 and a 65" projection in 2002. It also worked on all flatscreens, but I guess it wasn't designed for anything older.

I had the darn convergence pretty damn near perfect, but the center dot pattern showed it was off, so I did the center convergence and tried to touch up the rest. Didn't go as planned and now I have more areas with poor convergence. I guess the center convergence had a bigger effect on overall convergence than I thought it would. I would have left it as it was had I known.

I'll let you know how it goes when I do it in a completely dark room.

[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