Rejuventaing a '93 Sony trinitron. Should I try it?

[radiotvnut]

I was given a '93 Sony Trinitron today with the usual shorted HOT and power supply transistors caused by loose connections. The picture is still somewhat decent; but, the gray scale is a little off and it's not quite as sharp as it could be. This set has a AKB circuit. I tested the tube on my B&K 480 and the green reads in the upper bad area and the red and blue read in the very low end of the good scale. For some reason, B&K does not make a dedicated socket for these later Trinitron tubes. I made one from a socket removed from a junk board. Has anyone rejuvenated these newer Trinitron tubes with lasting results? I wanted to ask some opinions here before I try it. Id rather deal with a less than perfect picture than get a good picture after rejuvenation just to have the tube die in a week or two. I have rejuvenated regular CRT's over the years. Some held and some didn't. I don't really know how well Trinitrons tend to hold after rejuvenation BTW, I was going to try it on the "clean & balance" setting first. I believe that setting is less destructive than the rejuvenate function.

[MRX37]

Is it worth it to you to fix it? Having worked on several Trinitrons, the last one being very recently, I am not too fond of them. I do know that trinitron CRT's wear slowly, and are built differently from normal CRT's. It might be possible for your tester to give an inaccurate reading.

I had one Trinitron that had an awful picture, but playing with several adjustments inside the set improved it greatly.

[Chad Hauris]

Was this the age of set where if the tube got weak enough the AKB circuit would shut off the video? I remember some of the Trinitrons of the mid-late 90's with CRT's which started getting weak after only a few years having a "sound but no picture" symptom due to the AKB circuit cutting off the video.

[radiotvnut]

Yes, I think that's one of those sets. I had one like this a few months ago that turning the G2 control up produced a (crappy) picture. I also saw another 32" '99 model that would blink in and out. It was obvious the CRT was very weak in that one.

[Findm-Keepm]

Sony made some field changes to many of these sets to correct ABL and other deficiencies. I used to love to get sets that others deemed junk and fix them - simply by incorporating the field mods. It's been a while, though.

Here's one field mod that may be germane to the set you have:


Cheers,

[Findm-Keepm]

Another - hope it helps...

[colorfixer]

What's the issue happening on these sets? My parents have one of the 32" models on the list that in no way could the tube be shot with the light use they have on it.

My 25" XBR has about 18+ hard years on the tube and still looks bright and fresh.

[rcaman]

almost every sony that comes into our shop has a bad crt. either weak or shorted. just not the quality that they once was. steve

[YamahaFreak]

radiotvnut,

I think I may have picked up the very same set as you have here. I believe mine also has the shorted horiz. output. I'm not quite sure what to expect of the CRT when I fix that problem. There was an extremely large amount of built-up dust inside the set, which suggests to me that it was hard used for many years. If the tube is indeed weak, I will most likely need to rejuvenate, but I have no experience in that department, or even know what kind of equipment to use. Help appreciated.

[radiotvnut]

Well, I did rejuv mine and it seemed to work. How long it will last? Well, I guess time will tell. I'll probably end of giving this set to a friend who sets up at a flea market once a week. Maybe he can get a few $ for it.

Anyway, if you plan to check / rejuvenate CRT's; get something like a B&K 467, 470, 480, or 490. Stay away from the B&K's with lower model numbers. Their rejuvenate functions indeed do a good job of "cleaning" the cathode. Not only do they clean the crud off; but, they clean the emitting material off as well! The 467 and later ones have a less harsh rejuv function. To my knowledge, B&K does not make a dedicated socket for the later Sony CRT's. They do make a high priced universal adapter that clips on to the pins of the CRT. I decided just to make a dedicated adapter from a socket from a junk set.

These B&K testers can often be found on ebay for less than $100. Personally, it would be stupid to sink that much in one unless you plan on repairing TV's. If you know any TV technicians in your area; maybe one would check it for you. The easiest thing to do would be to spend the $12 on parts and hope for the best. You may actually be greeted with a nice picture!

Oh yes, the Sencore CR70 is another later model tester. I've never used one; but, I think they are decent testers. I don't know if there is a dedicated Sony trinitron socket for this one.

RCAman is correct about the quality going down. I have a low end 19" mid '80's and 2 '81 15" Sony's. All three still have strong CRT's.

[YamahaFreak]

I'll hope for the best, then! One of my boss's friends in the business has a bunch of what are marked "Color TV Briteners". They seem to be sockets with wires that fit onto something else. Are these devices related to the task at hand?

[radiotvnut]

Those brightners were real common from the '70's on back. They plug in between the set's CRT socket and the tube. What they do is boost the 6.3 volt filament supply to around 8 volts. This action causes the cathode to get hotter; thus, increasing emission. These brightners won't work with newer tubes. I've seen some sets with flyback powered filaments that actually had a warning inside the set claiming that the use of a brightner could draw too much current and burn out the flyback. There are, however, some newer solder in brightners that are designed to work with newer sets. I think they're about $15.

[Findm-Keepm]

Originally Posted by radiotvnut

There are, however, some newer solder in brightners that are designed to work with newer sets. I think they're about $15.

We made our own for a while - we had an Electronic Servicing and Technology magazine article that detailed how. We used them mostly for H-K shorts isolation, but you could wind one with a ratio to give the filaments a boost. Be careful - too much and you've got yourself a really bum CRT. These will only work with scan derived (flyback winding!) CRT filament supplies. Basically, you start with a toroid ring from an old common mode choke - we used ones from sacrificed Motorola Quasar chassis, about 1.5" in diameter. RCA sets also had a useful one - the one with the red and white wire, for those of you familiar with RCA's input chokes on their solid state sets. You wind two windings (we used 22 gauge SOLID wire) - one with more turns than the other (this is the secondary). I'm not all that sure of the ratio, and the ones we use now cover a variety of primary to secondary ratios required for various sets. I seem to recall Hitachi, GE (pre-RCA/Thomson) and some rare others having the odd ratios. Use two colors of wire to keep yourself straight on which is the primary and secondary. Pot the whole thing up with some RTV and use a plastic wire tie to fasten it to the chassis somehow, and you're done.

There's an article on the web - maybe on Anatek or elsewhere detailing how to make these, albeit for CRT computer monitors.

I'll see if I can find and scan the ES&T article.

Cheers,

[Bill R]

I used to just add an extra turn of wire to the filiment winding on the core of the flyback. That would raise the filiment voltage on the crt. Not all sets used this arangement but it is common.

Bill R

[Chad Hauris]

I have successfully done the flyback heater voltage trick with some older solid state sets such as RCA CTC-68's. Can't remember how many turns around the flyback though...I think I wound wire around the core till I got about 8 AC volts on a voltmeter. I used a DPDT switch on them to switch between the normal filament voltage and the "boosted" voltage. If the CRT is not too bad, switching the switch to the higher filament voltage for a few minutes and then back to normal often will provide a rejuvenating effect that will last for a while.