I took the set apart again, and tried tapping the various boards to see if I could reproduce the issue. Tapping and movement/flexing of the main board doesn't seem to have any correlation. Here are some photos of the boards. The joints look good to me.

Could it be a capacitor like andy said?

I'll pick up a voltage regulator just to see what happens.

Idk, honestly. If you're 100% certain the joints are good, capacitors are probably the next best suspect.

And it's gone again. Must be external.

Yes, some kind of line isolation. Line conducted interference can come from many things, for example, a motor in your furnace.

This stuff could also be radiated, which would be seen in analog reception, but won't be visible with digital sources. One place I lived, I got streaks in analog TV reception whenever the neighbor's furnace was running.

It comes and goes, so it's probably external.

Even though the source is external, I feel like the set being susceptible to these problems indicates a problem. Should I change the caps in the power circuit?

If you're not seeing any other indications of bad caps, you don't need to change them. It wouldn't help this.

If it is indeed external, and the problem isn't bad caps or anything else in the set, the solution is a voltage regulator like this?

That APC unit doesn't say anything about interference protection.

This Triplite unit does:
https://smile.amazon.com/Tripp-Lite-...ne+conditioner

data sheet:
https://assets.tripplite.com/product-pdfs/en/LS606M.pdf

However, no specs on the actual dB of suppression, so I would buy it from a place like Amazon with a lenient return policy, in case it doesn't fix your problem.

I ordered one, I’m interested to see if it fixes the issue.

The more research I do, the more I’m pointed to filter caps. Can they be the problem? Are they simple to change?

When the lines are there, they slowly scroll from bottom to top.

The caps that could reduce this problem are not the main power supply (electrolytic) caps, but small ones on the power input (if they exist). There may also be a relatively small coil or coils involved at that point. A schematic would help give a hint about what to look at.

The slow scroll tells you that the source is running from the 60.0 Hz power.
Is it a single line, or a bunch of lines? A bunch of lines, each rapidly flickering on and disappearing while the whole bunch slowly scrolls is probably motor interference.

In 1989 Sony was having Solder problems, I had a late 1989 built XBR that the picture starting randomly blacking out after about two years of use.

This was before the Internet or I would have known it was cold solder joints on a Horizontal transformer (not sure which one but not the flyback), it took about three tries of taking the set apart and soldering on the main board before I finally fixed it.

You can't always tell by looking if a solder joint is good or not, sometimes you just have to get in there and solder a bunch of stuff until you fix it.

It will usually be on a higher current connection though.

The Tripp Lite conditioner didn't help, the flickering lines are still there.

Next step is to check for cold solder joints. Eric, do you remember if tapping the set or boards reproduced the issue? In my case, they did not. Can I take the board out to work on? Are there any precautions to observe?

Shame, because the Trinitron has a great picture otherwise.

I took the set apart and tried tapping different parts of the mainboard, subboards, and the chassis again. Nothing reproduced the lines, or even caused an effect.

On my old Panasonic with a cold joint in the vertical section, tapping the set, or even walking around it, would cause the picture to jump around and compress vertically. With the cold joint repaired it was rock solid.

Here are the symptoms:

1) Flickering horizontal lines that come and go, sometimes present for hours, sometimes missing.

2) The lines slowly scroll from bottom to top when they are there.

The following causes were suggested:

1) Bad power. I tried the Tripp Lite conditioner mentioned earlier in the thread without success. x

2) Cold solder joints. My understanding is that these are susceptible to physical trauma, which I have tested by tapping various parts of the set.

3) Bad filter capacitors. Is there a way to eliminate this as an option?

4) Perhaps the set always had these lines.

I would really like to get this set working 100% again.

Two or three lines slowly scrolling up. Sometimes they are more sudden and are just black horizontal flickers (like in the video from the first post).

I looked at the video again, and I'm struck by the way the lines flashed on briefly with a second or so between occurrences. This is almost like some sort of mechanically intermittent connection.

Just as a wild idea, I would try flexing all video cables and power cords near both ends, where fraying/breakage is most likely. I'd do this for the power cords of everything else on the same circuit too. I'd also wiggle all power plugs in the wall sockets in case there is a socket with a loose ground. Also, open the set and resolder all the connections to components where the power comes in.

Perhaps try the set at a different location... perhaps the interference is local to your house or neighborhood. :scratch2:

jr