August 1977 RCA Colortrak

[vol.2]

Originally Posted by pac.attack76

You mean that top left looking from the back? Also looks like its had a history with color problems. Some changed the board out and left the old one inside...

Yes. You can probably get a decent idea of how it's working by measuring it without taking it out first.

Take you multimeter and measure across the whole pot to see what the resistance is, and then measure between the wiper and either side. find a way to clip the meter leads onto the terminals of the pot and turn the pot from side to side while looking at the meter. You should see the resistance change smoothly from one end of the pot to the other.

Based on what you have already said though, I would expect it to be completely shorted, or completely open if there's a problem with it at all.

If you can confirm that's it's behaving like a normal pot, then you can pretty much assume it's not broken and move on.

Looking at those other pictures, it seems like those old boards might need all the connectors cleaned really well, and the solder joints reflowed on anything that looks bad or is a physical connector.

Solder joints tend to fail on parts that are either heavy or take abuse, like connectors that get done and undone, and big heavy parts like the flyback or transformer, or big power resistors. You also want to check things that get hot, especially if they have been darkened or burned.

A lot of these kinds of issues will come down to basic stuff like that. Anything more advanced is probably going to require schematics.

[pac.attack76]

Originally Posted by vol.2

Yes. You can probably get a decent idea of how it's working by measuring it without taking it out first.

Take you multimeter and measure across the whole pot to see what the resistance is, and then measure between the wiper and either side. find a way to clip the meter leads onto the terminals of the pot and turn the pot from side to side while looking at the meter. You should see the resistance change smoothly from one end of the pot to the other.

Based on what you have already said though, I would expect it to be completely shorted, or completely open if there's a problem with it at all.

If you can confirm that's it's behaving like a normal pot, then you can pretty much assume it's not broken and move on.

Looking at those other pictures, it seems like those old boards might need all the connectors cleaned really well, and the solder joints reflowed on anything that looks bad or is a physical connector.

Solder joints tend to fail on parts that are either heavy or take abuse, like connectors that get done and undone, and big heavy parts like the flyback or transformer, or big power resistors. You also want to check things that get hot, especially if they have been darkened or burned.

A lot of these kinds of issues will come down to basic stuff like that. Anything more advanced is probably going to require schematics.

Before we get ahead of ourselves, what im wondering is did the color get affected by the yoke and rings being pushed back toward the socket? I've since moved everything up against the tube and straightened the image but I still have convergence issues as well.

[damen]

Convergence will not cause a lack of color. I would change that module you pictured. Most all of the color circuits are on it.

[vol.2]

It would probably take an afternoon to test every component on the board and reflow all of the solder.

Of course, the IC on the on board could also be at fault, which would be harder and possibly more expensive to replace, but it's worth spending a day and making one perfect board to test with first

Without the schematics, I wouldn't know which pins on that IC to probe for a chroma waveform, but possibly one of the other guys here with more 70s TV experience remembers what IC it is and what it's doing

But first things first; lots of these issues can be just bad solder joints and/or toasted passives

[pac.attack76]

Ill try pulling that board and see what's on the other side. Doubt I'd ever find a replacement. Better if I can fix one of these since there's 2 of them.

[pac.attack76]

Ok, weird. Pulled board out and figured I'd put the old one in to see what happens. Had to set color and tint but here's what I got. Should I look at anything else before I close it up?