Another day, another Trinitron

[YamahaFreak]

So another Trinitron followed me home today, that makes five. This one is a KV-27S26, and has its original remote control. It was a trash find, and it had a sign taped to it that read, "IT WORKS--WAIT 3 MIN."

Upon getting it home:

The set does power on, but there is an uncharacteristically long wait before the picture comes on, and once it IS on, the picture flicks between a black raster and the picture. This goes on for about five minutes. The flicking is worst when there is lots of white on the screen. The colors are also way off, seems like too much red/green and not enough blue? No amount of tinkering with the picture controls or the service menu adjustments fixes this problem. Sound is normal and working fine. Ideas? I was thinking the CRT may be going south, but I hope not. Could I possibly use the CRT from my (currently) dead KV-27S66 to test this theory?

Here is a short (~2 minutes) video showing the issues with this set:

http://img267.imageshack.us/img267/7285/1003616.mp4

[radiotvnut]

I hate to tell you; but, those symptoms are the sign of a weak CRT. Depending on how bad the tube is, you may be able to tweak the G2 control in order to stop it from blinking on and off. I have rejuvenated these tubes; but, they often don't hold up. They'll look good for a little while; then, they will fall back down again and usually look worse than before it was rejuvenated.

[YamahaFreak]

Originally Posted by radiotvnut

I hate to tell you; but, those symptoms are the sign of a weak CRT. Depending on how bad the tube is, you may be able to tweak the G2 control in order to stop it from blinking on and off. I have rejuvenated these tubes; but, they often don't hold up. They'll look good for a little while; then, they will fall back down again and usually look worse than before it was rejuvenated.

I thought so.

G2 is the 'screen' control on the flyback, right? I've tried that to attempt to brighten the picture--if I go too high, the screen just cuts to black. Once the set has been running for about five minutes, the screen stops flashing completely. Are my color problems the result of a weak CRT as well?

How long does he have for this world?

It's sooo weird, I've seen several Trinitrons far older than this 1997 set with CRTs in much better shape, especially the small sets. I guess it all depends on how much they were used. This one was full of dust.

[holmesuser01]

I have a Sony KV-27EXR25 built in 1991. The OEM kine lasted for 19 years, and I replaced it with a spare tube that I aquired back around 1995. It lives on...

I think that you Sony has the automatic aging circuitry like my EXR does. They blink when the kine starts getting weak.

List the tube number with us. Someone around here may have just the tube you need. It's worked for me!

[radiotvnut]

Yes, the color problems are a result of a weak CRT. I don't know exactly how it works; but, these sets have a circuit called AKB (auto kine bias). This circuit eliminated the traditional screen and drive set-up controls and automatically adjust the greyscale. When one or more guns inside the CRT get too weak for the AKB circuit to do it's job, it will cause the picture to blink on and off as the AKB circuit is trying to adjust the proper bias for the guns; but, the tube is too weak for the circuit to correct the problem.

One thing you might try is adding a CRT brightener. You can get them from places like MAT electronics and they solder in to the filament circuit. This will likely cure the problem; but, the fix will only be temporary. How long will the CRT last? It's hard to say, with or without a brightener. It could last a week, month, six months, or a year; but, it will likely die sooner rather than later.

Those later Sony CRT's, like much of everything else today, seems to have been built to a lesser standard. In my experience, the ones that hold up the best are tubes from the '80's. I have a mid '80's entry level 19" trinitron that still has a good CRT and it has seen lots of hours since I've had it over the last 8 or 9 years.

However, I've seen many of the '90's era sets with weak tubes. I have a B&K 470 CRT tester and, for some reason, B&K never made a dedicated socket for the '80's and later tubes. I finally made an adapter, using a socket from a junk chassis and any trinitron that's dead gets it's CRT checked before I go any further. Nothing is more frustrating than to fix a dead Sony (or, any other TV) and find out that the CRT is wasted.

[mbates14]

i noticed the horizontal deflection on both sides of the raster are pulling in. maybe worn out capacitors?

[YamahaFreak]

Thanks for the replies. My tube number is A68KZJ50X. If anyone's got one, let me know, even though I have no idea how I'd get it here. xD

As for a brightener, is there one made that fits late-model Trinitron tubes without modification? Or, is this a different kind of brightener, one that doesn't go between the CRT and socket?

mbates14, are you referencing my set, in the video, or another set?

EDIT: The tube in my 27S66 is not the same tube, so they cannot be interchanged.

[radiotvnut]

In the old days, brighteners were made to plug in between the CRT socket and the CRT. It was simply a transformer that boosted the filament voltage from 6.3 volts up to around 8 volts.

Since the '70's, there have been many different CRT bases in use. Therefore, the newer brighteners are designed to be soldered in place between the CRT filament supply and the CRT socket.

The current brighteners are pretty much universal and are designed to work with CRT filaments that are powered by the flyback transformer. Most TV's made over the last 30 years have flyback powered filaments. You really don't want to use an old step-up transformer style brightener with a flyback powered filament, as the brightener may draw excessive current through the flyback transformer and ruin it.

[andy]

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[mbates14]

I have a trinitron CRT computer monitor that the H-stat has no effect, and convergence is separated horizontally, and not vertically.

Anyone know of the correct resistance of the h-stat pot?

sorry for hijacking, but since we are talking about trinitron, this happens to jog my memory.

[YamahaFreak]

Originally Posted by andy

I've found Sony CRTs to be fairly interchangeable, regardless of type number. As long as the size, screen curvature, and mounting are the same, it will probably work. When installing an older CRT in a modern set, you may have to add the H-Stat pot to the neck board to get it to converge (there's usually a place for it on the board).

The sets in question are a KV-27S26 (bad CRT) and a KV-27S66 (bad HOT, et al) Both were built in 1997. You think they might be interchangeable?

[andy]

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[YamahaFreak]

Originally Posted by andy

Check that they both have the same type of CRT socket, and that the guns look the same. If they match, they should swap. Watch out for the fake Trinitrons that were being made in the 90's (they have in-line guns instead of a a trinitron gun).

Really? Someone was making fake Trinitron tubes? Interesting! Do they have genuine Sony labels on them?

I will check the socket on the 66 tomorrow to see if they match. I still want to get the 66 up and running by itself, but I wouldn't mind temporarily swapping the tubes just to see if it'd work. (this will also let me know the condition of the 66's tube, as I have not yet seen it powered up.)

[andy]

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[freakaftr8]

As for how long will it last? Could be days, could be months. Could go out tonight. When AKB flash is happening, that tube is about done if G2 doesnt help. You could Try the ol capacitor charge across the guns to try to prolong it (the thread is somewhere here on the forum).
I picked a 27" sony a while back that had a CRT on the way out doing the same deal. It's a crapshoot. Mine needen the resistor and HOT replaced. After I saw the picture I had wished I saved the ponys instead of investing it on that set. At least the chassis would be a good candiate for one that may have a busted CRT.