Question and comments.
First, in the newer Sony RPTVs I see alot of green CRTs getting weak. We give it a shot at rejuvination, but the greens don't seem to hold up. We play them for quite some time, long as possible. Alot of times they never make it out the door.
I have now rejuved a blue for the first time, and it did something I never saw before, it came through a life test with flying colors (figuratively). Not knowing just how much Sensore cuts the filament down, I did my own life test. Which is to turn the tester off for five seconds or so, and not disturb any bias controls. Leaving it in the read mode it came right back up immediately. I mean not even waiting for a warmup. I couldn't believe it, I turned it off for longer, perhaps closer to ten seconds, same thing. The set plays wonderfully and has not had a single arc or even a snap.
Now I have the following observations : When you rejuve the green it usually does not hold up, also it goes through a snapping/arcing phase, and then dies a slow death over the next few months. I have seen more blues get the G2 leakage.
With all this I wonder why. I know one thing different about the blue in RPTVs, the fact that Sony defocuses the blue in some RPTVs. Could this be a factor ? The green is of course as sharp as can be, but youi lose that when you rejuve it. Focus is not that big an issue with the blue, in fact the last one I worked on had no SVM coil or beam shaping magnets on it. I can see why.
Perhaps a slightly different G1 aperature size or some other factor, or like that it is defocused causes cloggage of the hole in the grid. That cloggage would have to come from cathode coating material, unless the evacuation and bombardment procees didn't go right during manufacture. We can only also speculate on why these tubes seem to want to get G2 leakage to a more positive electrode.
This common G2 leakage is probably to G3. I will probably eventually come up with a good clamping solution to fix it, but the problem will be when and if the leakage gets worse, and pulls down the G3. Unless someone thinks it's coming from the anode, I am going with this theory.
Now your problem is G1 to K which is dealt with in a different way. Put the tester away and get you a 22/150. If you want to be on the safe side use a 10. Charge it to 100V and apply it to the G1 and K.
Of course you only do this after you have tried a very light rujvination, rejuvination is a subtractive process (says Sencore) and if you subtract the protrusion in either element that shorts when it expands, you got it. Use the strongest rejuve level your tester has, but just tap the button. That will minimize damage to the good part of the cathode.
If you do this to the green or red you should readjust the beam shaping magnets, but with a blue, forget it. It might not even have them anyway. I don't have one in front of me right now.
One last observation, I rejuved that blue, and then had to turn the G2 down to at or near it's factory setting, when I do a green I have to turn it up. Perhaps this is an indication of how long the tube will last ?
Also, when you do the rejuve, not only do what I said, put the machine on it's highest setting, but you only tap the button. Like a very short horn honk. Like when you are not pissed. Tap it only. Then you must switch it to check for G1 shorts. Vary the filament voltage and watch the indicator. Tap with a screwdriver handle on the neck and watch the indicator carefully. Do this at high and low filament voltage. If the tests come up clean, ship it. If you get the slightest little flash or reading of leakage, consider hitting it again, again, oonly a tap. It is removing material and there ain't that much.
If you get the G1 short at lower filament voltages, you might want to reduce the filament voltage during rejuvination. Most testers crank it up during that function, so keep that in mind too. But then it might work better at a higher temperature, that would have to be your call. I would have to be there and see it myself to make the best judgement.
A G1 short is not always the end of the world. Frequently yes, but not always. At some point it becomes 'what do I have to lose ?'. If the customer gets another year out of it, great.
When the rejuve is successful in the case of a short, it usually lasts longer than if it was rejuved for being weak.
Slide that two cents under the door. When the vestibule gets covered, I'm going to pour a bucket of clear stuff all over it and have the coolest floor in town.
JURB