My Sony KV-27EXR25 has a weak kine. It is beginning to blink several times before the image comes up. The green is getting nasty, and is getting blue-ish in the dark areas. I've already done a minor adjustment of the screen controls, and the drive, but got no improvement after a few days.

Also, it is beginning to bleed red. I dont want to trash this set, as it has been a winner and very dependable.

This set uses an A68JMT50X tube.

I also have a dead KV-27TS32 that was 4 years old when it died. It is sitting in my storage building because I have another TS32 in my bedroom that I bought new. It has had some soldering issues, but has a lovely image after all these years.

This set has an A68KZJ50X tube.

I dont have any substitution information on these kines. What might be the chance that I can install the KZJ50X tube in the 2 year older EXR25?

I know that the dead set in my garage had an excellent image about a week before it died. It died due to a major failure of the power supply, and its owner just gave it to me rather than try to fix it. He's loaded, and didnt care to fix it. Bought a new one...

IF I cant swap these tubes, can a new or rebuilt tube still be had? I have never attempted to replace a trinitron tube before, just good old RCA, Zenith, Maggievox, etc, tubes. I know there are issues with magnets glued to the tube, etc. Not looking forward to it at all, but will do it if I have to. The keeper set fits perfectly where I have it, and like I said, had a perfect color image up until this year.

Thanks in advance, guys! :thmbsp:

Bruce

I did a similar swap several years ago and it worked fine. The one catch is that the older sets like the EXR series had a pot on the CRT board for the horizontal static convergence (H STAT). The more recent sets (possibly your TS) simply gound the convergence pin on the CRT (althouth there is often still a spot on the CRT board for the pot). Don't be surprised of you have to adjust the H Stat control to one extreme to get it to converge. You should swap the yokes between CRTs because the new one might be different.

I haven't gotten into the sets yet, but I just remembered that the EXR set has a big honker shield around the kine, and the TS32 has no shield. I believe I remember it being internally magnetically shielded. I wonder if that would make any difference?

I do plan to swap the yolks, unless they both have the same part number, which I highly doubt knowing Sony... If they do, though, it would save time doing the purity alignment.

I'm really glad that I bought paper copies of the service manuals for both of these sets! Its fun getting into the service mode on the EXR. :screwy:

I forgot to tell you this. A few months ago, I found an EXR25 in the trash, and fixed it. It is being used in my basement room, as it was tossed on the trashpile! The set I am referring to is one that I have had since it was a year old and a sale return. Had a roommate that watched TV 20+ hours a day, and he is the reason this set is heading south. :thumbsdn:

I appreciate the replys.

Bruce

I haven't gotten into the sets yet, but I just remembered that the EXR set has a big honker shield around the kine, and the TS32 has no shield. I believe I remember it being internally magnetically shielded. I wonder if that would make any difference?

I do plan to swap the yolks, unless they both have the same part number, which I highly doubt knowing Sony... If they do, though, it would save time doing the purity alignment.



The shield won't make any difference. If anything, it will make it less sensitive to magnetic fields.

Definitely keep the yoke if they are the same.

Just wondering if it might be easier to fix the dead set? Is it in good shape otherwise?

No it is not. Several modules have been snatched and there are burns on the main board from the power supply failure. AND it wont fit in the cabinet that my EXR set is in! There is about a 1 1/2" difference in the height!

The EXR set is the one.

You could swap the yokes and power the new CRT while it's still in the old cabinet. This will tell you if it's going to work before you pull everything apart. There should be enough slack in the wires to connect everything. Don't forget to ground the CRT.

This one I have plenty of experience on... The KZJ is the correct swap for the JMT. I did about 100 of them after the Northridge earthquake. You can use the shield from the old tube if you want, but you don't have to. The main difference between the two types is that the KZJ has the shield inside the tube. The guns are identical.

Only word of caution will be to set the G2 voltage AT OR BELOW what it was set at in the KV-27TS32. If you set it higher, the tube will die fast! However, you can't see what the donor TV was set at. Therefore, just be very careful to set the G2 well-below where you see any retrace lines.

Charles

THIS all tells me what I need to know. This is gonna be a winter project. And my first Sony tube swap. I cant take pictures, but I can keep you guys informed on the progress.

Andy, I've done that in the past with older RCA's, etc, sets. It had not even crossed my mind to try what you said. Being that this is the first Sony transplant, I tend to forget that its been done before, but on different scale.

If I have to swap yolks, I dread the magnet installations.

Bruce

I can't remember for sure, but I BELIEVE you can leave the yoke and convergence rings in place, undisturbed, and swap the fully dressed tube. The yokes LOOK a bit different, but I think they're electrically swappable. At worst, if the yokes aren't electrically the same, you might get a slightly shrunken picture or bad convergence. Then you'll have to go ahead and change the yokes. Those sets also have a velocity modulation coil, I recall. That too can be left on the tube as long as the plugs are the same.

Charles

I've got a Sony KV27S20 that I got for free at a yard sale, I think the chassis is ok but the CRT is dead, dead, dead. I checked it and it has absolutely no emission, nothing after trying the rejuvenate-restore. I'm going to trash it this weekend, if somebody can use the boards you can have them for the postage.

Only word of caution will be to set the G2 voltage AT OR BELOW what it was set at in the KV-27TS32. If you set it higher, the tube will die fast! However, you can't see what the donor TV was set at. Therefore, just be very careful to set the G2 well-below where you see any retrace lines.

Charles


I've heard this before, but can you explain why the G2 setting affects CRT life? I would have expected the cathode life to only depend on the cathode current, regardless of which combination of cathode and G2 voltages result in that current. Why would a more positive cathode not last as long?

I wish I could explain, but that would maybe best be answered by an engineer. (Hey Tom Ryan or Colortel???) I think it could be that a CRT "gets used to" a certain cathode current, and the cathode coating deteriorates at a certain even pace. Then all of a sudden the temperature is changed due to a different current load (heat): Cathode coating cracks or fails somehow. Just an uneducated guess.

Similarly, a CRT could be excellent for 20 years with regular daily use. Then put the set in a closet unplugged for a year, and wham! Dead CRT. Cathode coating was heated & cooled at a certain pace, then left cold and static for a year. That seems only to be true of 1980s & newer tubes though.

Not that this is any analogy, but it is also my experience that you cannot swap a car battery among cars. It will be fine in one car for years, then put it in another car and it's shot within a month. Different charge & discharge rates between the cars!

Hopefully someone in the know can weigh in on this one!

Charles

Somewhat similiar: my cordless phone at work stays out of the charger until the low battery light starts to flash-almost a week between charges. This phone is 6 years old, original battery. At home our phone is newer, maybe 4 years old, but my wife likes to leave it in the cradle. It now will hold a charge no more than a few hours. If the battery doesn't get used to a deep cycle it loses the ability to do it. I could understand if CRTs are the same.

I wish I could explain, but that would maybe best be answered by an engineer. (Hey Tom Ryan or Colortel???) I think it could be that a CRT "gets used to" a certain cathode current, and the cathode coating deteriorates at a certain even pace. Then all of a sudden the temperature is changed due to a different current load (heat): Cathode coating cracks or fails somehow. Just an uneducated guess.

So your saying it's the change in the G2 voltage that hurts the CRT? So if a new CRT is setup with a higher than normal G2 voltage, its life won't be negatively impacted?

How often have you seen this happen? I've done quite a few CRT swaps and I've never had any problems with the swapped CRTs. I normally adjust the G2 on AKB sets by looking at the cathode signals on a scope. I adjust it so that the video has the widest dynamic range possible while not crushing the blanking pulses. This would mean that they G2 is set as high as possible without retrace lines. My logic is that as the CRT ages, the cathodes will need to be biased at a lower and lower voltage (to make the picture brighter), so start with the highest cathode voltage possible.

It has to be related to cathode voltage, not current since it takes the same amount of current to produce the same brightness picture, no matter what the cathode and G2 voltages are.

Has anyone see this happen with other types of tubes? It seems like the same thing could happen to audio tubes.

So your saying it's the change in the G2 voltage that hurts the CRT? So if a new CRT is setup with a higher than normal G2 voltage, its life won't be negatively impacted?

How often have you seen this happen? I've done quite a few CRT swaps and I've never had any problems with the swapped CRTs. I normally adjust the G2 on AKB sets by looking at the cathode signals on a scope. I adjust it so that the video has the widest dynamic range possible while not crushing the blanking pulses. This would mean that they G2 is set as high as possible without retrace lines. My logic is that as the CRT ages, the cathodes will need to be biased at a lower and lower voltage (to make the picture brighter), so start with the highest cathode voltage possible.

It has to be related to cathode voltage, not current since it takes the same amount of current to produce the same brightness picture, no matter what the cathode and G2 voltages are.

Has anyone see this happen with other types of tubes? It seems like the same thing could happen to audio tubes.

Well, that's why I defer to an engineer...

My experiences with this problem are only on used tubes, not new. I've had it happen on all types of color CRTS, particularly with Sony direct-view tubes, and Mitsubishi projection tubes. And with the Mitsubishi, I ALWAYS set up with a scope per the book. With the older Mitsubishis, the procedure is to set the G2 pots to min, Drive to center, and scope the collector of the green video output (cathode of CRT)... Set the Sub Brite to see 180 vdc on the CRT cathode. Then eyeball the G2 pots at lowlight and finish with the drives.

That works great on new CRTs, but if I do that on a set of used ones, it's good night nurse!

Charles

I know we were advised to fire up our tube-pickup (Saticon) HDTv camera at least every six months, supposedly to prevent deterioration due to gas, though I never found out if that was really the cause or how the gas would be removed by operation. Anyhow, those pickup tubes had very small cathodes and gun apertures to get the required resolution, and that's why they were so sensitive to use conditions. I never thought that "big" CRT cathodes would be so sensitive, so it will be interesting if some expert chimes in here to tell us the mechanism for deterioration.