CurtPalme.com Home Theater Forum

[macgyver655]

I sent a bunch of you guys some snippits as you requested. I am going to post just this one for now though. I also may have some future stuff.

This document section applies to cathodes, which means, it doesn't matter who makes it. A cathode is a cathode is a cathode. Some are just made a little different.

These words are from an engineer at Philips electronics who specializes in tubes. This document section is on rejuvenation.

C&P

This also helps for poisoned cathodes. Cathodes that have been operated too long on a too low heater voltage get poisoned, meaning that the Ba/Sr-oxide gets chemically binded, leading to a higher working voltage. Indeed, only oxide cathodes can be rejuvenated this way. Impregnated cathodes have a more sudden death mechanism and can not be regenerated in this way.

[johnnynickel]

Well, even with 70k standby hours the blue tube was able to be rejuvenated really very easily using a CR-70. The process helped the green tube tremendously also, even though I couldn't get it to "flash", but its still too dim. Its the only one that's P43, so the settings might need to be tweeked to work properly, but I think its only going to get as good as I've got it, which is just too dim. Is this a situation where the tube can be rebuilt? It doesn't need new phosphor, but can you get one without the other? Its probably more viable to try and find a replacement green tube. Just thought I'd update in case anyone was wondering. Even after 70,000 standby hours the blue tube was able to be rejuvenated easily and the red tube is working fine.

[macgyver655]

[gjaky]

Mac, the standby means on marquee the same as the 'pic mute' on a NEC, so the set is fully powered just the picture muted, in this sense it is not a big surprise that the tubes are weak after 70k hrs.
BUT
I am currently working my "new" marquee 9000, and I have some problem too.
The hour counter says that 5700hrs on tubes and 16hrs in stby (pic mute). The tubes look decent red and blue absolutely free from burn, on green -only during bellow replacement- saw some sign of wear. Heater voltage is ok (~6,2V)
I tried to adjust grayscale according to Tim's website.
I set the tubes to the default (RD:35, RG2:60, GD:90, GG2:60, BD:50, BG2:60)
The problem is that the green needs only 42 on G2, to see the second darkest square, but on red needs up to G2 75, on blue around 68.
I disassembled the LVPS of the set, and it was full of dust, however the chassis fans were quite clean, due to the fact that the ps fans still working during power off, and the filament gets the 4V, I guess this machine ran a lot in off state. But why is this big difference between tubes? The blue tube's serial no. begins with 08.., the Red's begins with 55.. the green's begins with 49..
Can someone explain this to me?
Do you think the rejuvenating also would help?

[macgyver655]

Well I'm not going to speak for Tim but based on the numbers you got I dont see a problem. Your numbers indicate that your green is real strong, blue is still nice and strong and the Red is still acceptable. But you also have to remember that I believe Tims statement is for new Marquee's which I think it says so. But he can answer those questions more directly.

In the end they are just numbers. If you have good light output and can achieve good color balance and cutoff then I don't see a problem.

Rejuvenation should only be attempted in more severe cases because a tube can be permanently damaged from the process.

[macgyver655]

Oh, and yes, I completely understand the concept of pic mute and Marquee standby....