Trinitron Horizontal Flicker
 

This 1989 KV-20TS20 Trinitron has a horizontal line flickering problem on all sources. They appear to be random. This is a still image for example. It's subtle but it's there. I'd like to fix it.

https://youtu.be/9x77Ha8or4A?t=8s

What is the source of the issue? Capacitors in the power circuit? Tapping the set for cold joints doesn't do anything.

You may have to slap it harder ! Still look for cold joints on the
hoz drive transformer. After that the hoz out & flyback area.

Cold joints on the H drive are common to most brands for many years.
when working on ANY set from the mid 70's on always resolder them.
If they keep up you could blow the HOT & power supply.

Your problem is very subtle so if its not a PC con it will be very hard to smoke out. You may have to wait for it to get worse or fails first.....

Good luck
73 Zeno:smoke:
LFOD !

Okay, thank you.

I am not experienced with electronics repair. Is there a book to get me up to speed?

For example, I think I know what a cold solder joint is (an intermittent connection due to cracked solder), but I do not know how to look for it or repair it. Perhaps it would be best if I practice on something else first.

This looks like a good starting point.

I took the set apart and tried to tap various areas of the board with a screwdriver to see if I could reproduce the issue, and I wasn't able to.

Then I noticed that the flickering seemed to be gone. I tried plugging only the TV and source into the AC socket, and the flickering remained gone. Perhaps another piece of equipment was causing interference in the power.

If it's anything like my old Trinitron, ALL the solder joints will be bad. Get yourself a REALLY good magnifying glass, and actually remove all the circuit boards and just look over every square inch of them under a good light (I prefer sunlight). Cracked solder joints ('cold joints') are usually very obvious when you can see them well. A good joint should be smooth and shiny, a bad one will have an actual crack in it, though it's hard to catch unless you're REALLY paying attention.

Problem areas on any pcb are anything large sticking up from the board (big caps, plug sockets, soldered-on riser boards) and otherwise anything that exerts physical stress to the joints.

Speaking of which, doesn't that TV have riser boards plugged into the main board? Maybe the contacts are dirty. Blow it out like a Nintendo cartridge.

Here are some photos of the boards.

https://p836iw.by3301.livefilestore....&cropmode=none

https://p80aja.by3301.livefilestore....&cropmode=none

When I took the back off, I vacuumed most of the dust off as well. The flickering has not returned yet. Next step is to plug everything back in one by one and see if the flickering returns.

Thanks for the advice about looking for cold joints, I will need it if Trinitrons are susceptible to bad joints.

With any luck it was just a fluke.

...

I tell you one thing: it's way too damn dusty in there. Blow a bunch of compressed air on everything. Dust can technically conduct electricity, depending on conditions.

high volumes of dust = a high hour set.

Or a low hour set that spent its life in an oppressively dusty environment. :yuck:

Once I dust out the inside with compressed air, is there anything else I can do for preventative maintenance? I've heard it's a good idea not to use sets when it's hot or humid because that can lead to cracked solder joints.

My old Panasonic works perfectly (and flicker-free for what it's worth) since '94, but did develop a bad joint in the vertical section about 10 years ago that had to be repaired as well as a sticking power relay. I never dusted it out until the problem had surfaced.

That was exactly it. I have isolated the flicker to the charger for my MacBook computer. When the charger isn't connected, the flicker disappears.

Some sets develop cold joints naturally with time...They sometimes don't size the heat sinks big enough. The chips will run cooler than their max operating temp and will work fine, but will be hot enough to cause thermal stress to the solder and or bring it to the edge of melting...Not much you can do about it but open it once every few years of service and check on it.

The flickering has returned. I’m almost certain it wasn’t there earlier. The only thing that changed is I dusted out the back again.

I tried plugging into three different outlets without success. Only one thing is connected to power, the TV, and it still flickers.

If it is an external power problem, how can it be remedied?

Voltage regulating power line isolation transformer.

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

Ditto Exactly what I was just thinkin. In todays world almost anything
that plugs in or even on batteries can cause subtle problems like this.
Basically they are all little interference transmitters due to cheap design,
quality, & failures. It can get into the set via the line, antenna or directly
into the chassis. 3 case histories ...........

1) When I sent CW it would turn one of my Zeniths on & off.
A better ground for the transceiver fixed that.

2) Brand new Zenith had lines on all low channels not on old set.
(It actually did but wasnt sharp enuf to see them much) It was the
only set on ears. Cure was a calculator was upstairs recharging.

3) Just had a planned black out. What to do ? Listen to AM radio !
Almost every channel had a listenable signal as far as 300 miles
daytime. When the power came back it went back to just a few powerful
locals & lots of garbage.

enuf fer now
73 Zeno:smoke:
LFOD !

Out of genuine interest, I picked up another Trinitron (for free), a 1992 KV-20TS27.

It has exactly the same flickering issue! It must be something in the power, and the Tripp Lite isn’t catching it. Any suggestions for a better unit?

What’s also interesting is that the ‘92 Trinitron is much fuzzier, even the OSD. I wonder if the set was always like this or it’s age-related.

A cheap set may actually work better BUT I got a feelin you will see
it on anything since you know about it.
You could try tracking down the source. Turn off all house breakers
except the one the TV is on. If it goes away turn them on one at a
time til it comes back. Then you know the line & can unplug things.
If you cant get rid if it turn the breakers back off & walk around with
an AM radio listening for hot spots. Remember it can be something on batteries
causing it. OH watch for loose cables on other things in the house.

good luck Zeno:smoke:
LFOD !

Sounds good! Maybe I’ll try another power conditioner.

By the way, my ‘94 Panasonic (RF-only cheap set) is immune.

I got it. Putting everything else on the Tripp Lite, and connecting the Trinitron directly to the wall removes the lines completely.

Too bad the second Trinitron's tube is completely worn out, it is nice.

The '89 KV-20TS20 Trinitron has an interesting picture. The white sections are very bright, even with picture low, and the picture is very sharp, but it seems like dark details (such as shadows) have very little detail, even with brightness calibrated. The problem is very similar to the one described here.

I don't know if it is simply the decoder or something with the tube or circuitry. It does make some scenes appear very dim.

Screen shot time !
The whole screen from a DVD or VCR not a game or cartoon.
Sounds like a common problem, gotta see it 1st.


73 Zeno:smoke:
LFOD !

Here is a photo from the show Becker. The first is the Trinitron, and the other is a screenshot from the DVD. My '94 RF-only Panasonic displays something far closer to the screenshot.

https://ceqa0g.by3301.livefilestore....&cropmode=none

https://cequ0g.by3301.livefilestore....&cropmode=none

Look at his tie, her hair, and the sign in the background. Picture is at 25%. If the brightness is turned up further, the blacks become gray.

Is the Sony being fed the same RF signal as the Panasonic that doesn't have the problem, or are you using a composite input on the Sony? Whatever is the cause, blacks are being clipped before the signal gets to the brightness control, if turning up the brightness just makes them gray.

Well, now you could find out what's causing it by unplugging one thing at a time from the Tripp Lite and plugging it directly onto the line with the TV.

The photo is of composite, but I tried RF and it looks the same.

Here is a photo of the Panasonic showing the same scene.

https://ceqb0g.by3301.livefilestore....&cropmode=none

There's a book in my university library covering CRT repair from 1989, it might be a useful resource for me.