Alternative Way of Adjusting G2s (25EC58)

[old_tv_nut]

OK, you may have two problems combining to give this effect.
The change with fine tuning, channel change back and forth, could be a tuner issue. Then, as the change in tuning affects the color level, it could be some kind of overload in the color circuits related to the ACG.

First, get the fine tuning right. Turn off the AFT, and set the fine tuning manually. turning one way should make the picture blurrier and reduce the color signal. Turning the other way should make the color signal stronger. There may be little visible change in the color strength due to the internal automatic color control (ACC), but eventually on this end of the adjustment, the picture will show "wormy" interference that moves with the sound content. When you see the sound interference, turn back the fine tuning until the interference disappears. Once the fine tuning is correct, try adjusting the ACG.

[TinCanAlley]

Originally Posted by old_tv_nut

OK, you may have two problems combining to give this effect.
The change with fine tuning, channel change back and forth, could be a tuner issue. Then, as the change in tuning affects the color level, it could be some kind of overload in the color circuits related to the ACG.

First, get the fine tuning right. Turn off the AFT, and set the fine tuning manually. turning one way should make the picture blurrier and reduce the color signal. Turning the other way should make the color signal stronger. There may be little visible change in the color strength due to the internal automatic color control (ACC), but eventually on this end of the adjustment, the picture will show "wormy" interference that moves with the sound content. When you see the sound interference, turn back the fine tuning until the interference disappears. Once the fine tuning is correct, try adjusting the ACG.

I adjusted the ACG and ACC while I was there. Both set as per SM.

I'm attaching two pics. First one is after adjusting the tuner, ACC and ACG. The second is about 5 minutes afterwards. I'm starting to think it's somewhere tint is coming from. If I adjust tint, I get it back to what it was before. I tapped the pot and knob, but couldn't get a reaction in the tint, so I'm kind of certain it's not the pot.

Added one more and it again shows the blue over the red, although the red isn't red anymore.

[TinCanAlley]

Just noticed something. When I was adjusting the ACC, it said to short two points, read voltage, remove short and adjust ACC to same voltage as when shorted. I did this and the voltage was 16.8V. I've been going over the schematics and it shows the ACC points on the Sub Carrier Regen as being 8.6V to and from the Chroma module. The voltage I measured was twice as much, but other than the schematic, I can't find anything about voltage level for the ACC and whether it goes up or down from the voltage in the schematic.

[TinCanAlley]

One more update.....

I put up the color bars again and flipped the align switch. The colors were rolling through the bars again. I readjusted the ACG and found there are three spots where the rolling slows down and reverses. I picked another spot and went back and forth to get the rolling to stop, for the most part. I readjusted color and tint and got a great looking image.

Five minutes later, the tint had changed again to the purple side. I pulled and pushed the tint knob and it went back to normal. I find it had to believe the pot is bad as it is smooth changing the tint when rotating. Nothing odd happens when rotating it, so I don't know if pulling and pushing it did anything and I just got lucky. I'm going to press the chromatic button and adjust the inner pot and see if that one can keep tint setting.

The blue that showed up in the red, I saw the same thing when the color bars were rolling while adjusting the ACG. So I'm assuming that is the cause of it. I'm going to get out the scope tomorrow and check the waveforms as noted in the SM. Hopefully that will give some insight.

If I can just fix this issue, all will be well. I am very happy with the image when it stays adjusted.