CurtPalme.com Home Theater Forum

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I know I made photos of all those tubes in that lot. I stripped out, I think it was three, 808s at the local recycler's.

But it was so long ago, why even bring it up? There's just no point to even doing it. It's history, water under the bridge,
and whatever you paid, I refunded without giving you any grief about it.

**kal** · Posted: Fri Jun 09, 2017 3:50 pm Post subject:

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

That was a long time ago. I seem to remember that I made photos of those tubes but I know that if I did, the computer that they were uploaded to no longer exists so there's no way for me to dig them up or prove it and it doesn't matter anyway.

Kal, my brother got divorced because his ex-wife had the nastiest habit of throwing past sins into today's fight and you are doing exactly the same thing. It's absurd, and it's reprehensible conduct which stinks of passive-aggressiveness.

While I tend to trust your judgement in some areas, the truth is that you have some really and truly NASTY aspects to your personality and I'm very much aware of them.

Oh, as for additional context regarding my integrity as a businessman of sorts, I will refer you to my ebay record:

http://www.ebay.com/usr/quantummechanic

Yes, that's me. Feedback score of 718, 100 percent positive. Member since 1999.

I'm not perfect, no argument there, but I stand behind what I sell and if there IS a problem, I make it right,
without turning into a whiny B#### about it.

**kal** · Posted: Sat Jun 10, 2017 2:17 am Post subject:

If everything is perfect, then you have nothing to worry about. Good luck selling stuff.

Kal

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

My total sales over the years is in six figures, but my profit margin is considerably less although certainly not zero.

It's been a good supplement to my income. And at times, my only income.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

I've tentatively diagnosed this weird tube's condition as having abnormally high gain and sensitivity. If that is the case, then its gain should naturally reduce as the tube gets some hours on it.

the dude · Joined: 11 Sep 2013 Posts: 179

I had this problem on a pt22. It is caused by cathode material that is disposed over the time in the very tiny gap between the cathode and the G1 grid. This can cause a very high impedance short that "steals" away some amount of the cathode current so the ABL current sense circuit get fooled and turns G2 a bit to high. I don't have a explaination of flicker and noise, but i guess the short behaves in a some non linear manner.

I also had succuess repairing this on one tube using a electroshocker with 50kv output. I connected it to cathode and g1 and *shortly* "shocked" the tube. I saw little sparks in the vacuum, looked quite funny. No guarantee of course, i would not try this on a working one. For me it worked perfectly. There are professional crt service devices out there that can also remove shorts.

cmjohnson · Joined: 03 Apr 2006 Posts: 5180 Location: Buried under G90s

Yeah, I've used a Sencore CRT restorer before. Sometimes they can fix a tube. But sometimes they can make a weak tube weaker.

What i'm going to do with this one is to run it all by itself with some video content for a while and see what happens.

If I'm right and it's just got more gain than normal, it should "quiet down" after being run for some undefined length of time.

I've got it installed in one of my G90s and I'll just run it with red and blue cut off. Give it a few days of operation and see what happens next.

I'm not sure if I want to risk the shock treatment. That's pretty much a flip of the coin. You either get a fixed tube or it ends up REALLY broken when it's usable in its current state. OK, maybe a bit noisy, but not enough to really notice on the screen.

After maybe a week of just being run as a normal tube, maybe it'll be better? No way to know but to try.

the dude · Joined: 11 Sep 2013 Posts: 179

Hm, when i had this problem it got worse and worse over time until green flickering lines became visible in dark scenes. Don't expect the disposits simply go away, the cathode will emmit even more material. But maybe some carefully knocking on the tubes neck may help.

I don't know this tube restorer, but if it just tries to blow away the oxide to reactivate the cathode this may work or not for a weak one, as you said. But blowing out shorts is a different task, the Müter crt service devices can do this as well.

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

**Curt Palme** · Posted: Mon Jun 19, 2017 12:15 am Post subject:

For the record, I've never had any success rejuvenating CRT projection tubes. I too have the Sencore 7000, made a custom CRT socket for the tubes, but never got anywhere with them. Regular CRT TV tubes, no problem!

jbltecnicspro · Joined: 23 Apr 2016 Posts: 512

the dude · Joined: 11 Sep 2013 Posts: 179

Projection tubes have very small spot size AND high current. I think due to this its not possible to reactivate them. Restorers overheat the cathode and apply very high currents in order to blow away inactive material and to uncover unused cathode material. In the beginning of TV restoration was easy, then with "modern" oxide cathodes it got tricky, and with projection tubes it is allmost impossible.

I also believe that most tubes die because of worn phosphor, not cathodes. If a tube dies of worn cathode it may be due to incorrect heating voltage. But removing shorts using a restorer that is able to do this may work well.