Cathode poisoning?

[newxito]

Is that cathode poisoning? I have checked the voltage and the anode resistor and the values seem to be as recommended: 170V and 8.2k

Is it possible to fix that? It's starting with the 6 as well. All other tubes are working great.

[Paul Andrews]

It looks like it, OTH if other digits are suddenly showing the same, it could be a loss of pressure. Is that a Dalibor tube? If so I would contact him directly. If not, you could try to rejuvenate it using the same anode resistor and, say, 200V. Apply that to the affected digits until they clear up, which could take anything from a few minutes to hours.

[gregebert]

I suggest you measure the current to make sure it's in the correct range. It's easiest to do that by measuring the voltage across the anode resistor, and use ohms law to calculate the current.

[newxito]

Thanks for your suggestions. I just remembered that I bought this kit years ago. Time to build it. I will report any improvement...

[Dalibor]

Hi, this is our tube, looks like the beginning of a leakage. Healing will help in this case, but the issue will most likely return over time. The tube is under warranty, so we would replace it.

Please send me the serial number of the tube for my statistics, I guess it will be in #1XXX.

Some stats if you are interested :-)

X - serial number

Y - % of reported leaks

Best regards,  

[newxito]

Good guess :-) 

The serial number is indeed #1XXX. I PM you the number.

Good to know that the tube is still under warranty, that's great, thanks!

[Dalibor]

Sure, 10 years warranty, it will take a few more years before the first tubes' warranty expires :-)

Statistics attached now - the image didn't make it to the previous post..

[newxito]

The statistic looks really good, you kept improving the process! 

[Mac Doktor]

Forgot to send this...

On Sep 26, 2020, at 4:36 AM, Dalibor <dal...@farny.cz> wrote:

Sure, 10 years warranty, it will take a few more years before the first tubes' warranty expires :-)

My Herman Miller computer chair has a TWELVE year warranty. I doubt that it's going to last anywhere near that long, though. I'm not sure about the load it's under. 

It's actually my second chair. The first one lasted about seven years. I got to pick the options and colors. For the latter I chose black with red fabric. Looks like a Ferrari.

Terry Bowman, KA4HJH
"The Mac Doctor"

https://www.astarcloseup.com/

"Every kid starts out as a natural-born scientist, and then we beat it out of them. A few trickle through the system with their wonder and enthusiasm for science intact."—Carl Sagan, Psychology Today, 1996

[newxito]

10 days ago, I got the replacement tube, great support from Dalibor. 

The new tube is now in the clock and I have tried to heal the old one. I had some success, the 8 and the 6 look a lot better after applying 200V during 24h with a 4.7k anode resistor... don't do that!   :-)  

But now also the 5 has problems, so Dalibor was right, the tube is probably leaking.

[gregebert]

Do you see any air bubbles in the crimp at the base of the tube ?

[dal...@farny.cz]

Even when healing certain digits only, it is necessary to exercise them all - otherwise, the impurities that make the cathodes poisoned will move to stationary cathodes, poisoning them (5). But from the pictures, I expect the tube was leaky (at least for some time), the air that got into it will accelerate the poisoning overtime even if you heal it successfully now.

As for the air bubbles - there can be isolated bubbles in the glass (this is ok), but when a bubble is found sitting on the wire itself, we reject such a stem - such a bubble can be connected with a microscopic channel to the inside of the tube ("virtual leak") and contaminate the tube long after successfully passing all other tests.

Cheers

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[newxito]

I can see some tiny bubbles in the glass but not near the wires. I'll try to heal the 5 and then go through all the digits.

[Bill Notfaded]

I love my Herman Miller Aeron Chairs.  No fabric to get dirty you just wipe it off and you're good to go.  I've got one at work and one at home in my lab.  You do get what you pay for when it comes to chairs!

https://images-na.ssl-images-amazon.com/images/I/71ijzrsAAPL._AC_SL1500_.jpg

Bill

[Bill Notfaded]

As for the OP you can't argue with Dalibors history and he stands by his product.  Putting up the stats that show his continual improvement in the tubes is legit!

Bill