Is this IN-18 bad?

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6 years 7 months ago #2995 by mathewbeall
Hi Folks,

I just got a batch of (6) IN-18 tubes and one of them displays this odd purple color only when the #1 segment is lit up. Is this something that will go away with time or should I have the person send me another IN-18 to replace this one?

Much Thanks,

Matt
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6 years 7 months ago #2996 by GreyFox
I have one like that - its a replacement tube and I have the blue dots on the #1 only. From what I understand it indicates that the tube is over driven. Or it has too much power driving the digit.

Let there be neon light!

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6 years 7 months ago #2997 by mathewbeall
That is odd - it doesn't happen with any of my other tubes in that socket - which would lead me to believe that it isn't an issue with overdriving.

Matt

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6 years 7 months ago #2998 by Nocrotec
Hi!
This is the well known Blue Spot problem!
Here is the description I sent to Brian today:

The blue spots are caused by the following circumstances:
If low voltage drivers are used, as example the 74141 drivers, the cold cathode voltage (non glowing cathode voltage) drops down to the clamping voltage of the output transistors (70-100 Volts).
In this state the mercury slightly breaks down, slightly ionizes, and little current flows from the anode, through all 9 non glowing cathodes through the Z-Diodes (Driver protection diodes) to ground. And that
inonized mercury can be seen as blue spots in the tube.
That's all.
;-)
How to avoid it?
Don't use any off cathode clamping voltage, but high voltage drivers.
And again, for the thousandth time: YOU CAN NOT DRIVE ALL IN-18 TUBES WITH 74141 DRIVERS!!!! SO DO NEVER USE THEM!
IF A BLUE SPOT APPEARS IN YOUR IN-18 TUBE THE CIRCUIT IS WRONG, NOT THE TUBE!
Look here:
www.nocrotec.com/shop/product_info.php/l...Dream-Nixie-Uhr.html
Dieter

If you are in a rush, walk slowly!
www.nocrotec.com
The following user(s) said Thank You: Stuckey

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6 years 7 months ago #2999 by mathewbeall
Ahhhh - ok... I will try this tube in another clock I have that doesn't use those drivers to validate.... thanks for the information!

Matt

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6 years 7 months ago #3001 by GreyFox
Bad circuit - Hmmmm my kit is one from tubehobby and the tube there that outgassed worked just fine. The replacement IN-18 has the blue dots for the #1 digit. So am I now faced with a bad circuit or a tube that is again out gassing?

Maybe I should switch kits ag go with a different setup.

Let there be neon light!

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6 years 7 months ago - 6 years 7 months ago #3002 by Nocrotec
You have understood it wrong.

> or a tube that is again out gassing?

NO!!!! NO and NO!
If a blue spot appears, it has NOTHING(!!!) to do with a bad tube or outgassing or something.
Read again my description where it comes from.
The low voltage drivers are the problem.
Also if tube x work with the driver, tube y may not work.
Why?
Of course the amount of mercury is different in the tubes.
But the more mercury, the longer the tubes life.
So your tube with the blue spots IS BETTER(!!!!) than the others you have and it will work perfect without blue spots, for a long long time (if driven correctly)

So it is as I said:
IF A BLUE SPOT APPEARS IN YOUR IN-18 TUBE THE CIRCUIT IS WRONG, NOT THE TUBE!

If you are in a rush, walk slowly!
www.nocrotec.com
Last Edit: 6 years 7 months ago by Nocrotec.
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6 years 7 months ago #3004 by GreyFox
Sorry I was distracted when I wrote that up... Should have re-read it.

Makes sense that the tube has a differnt Mercury content. I'll compair the tube dates...

Maybe this is a good reason to move to my TaylorEdge kit. And move off the Tubehobby kit. TaylorEdge kit has HV driver on all the pins. Tubehobby has a Multiplexed setup and the clock does hum so maybe that is what I'll do to resolve that issue.

Let there be neon light!

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6 years 7 months ago #3005 by Nocrotec
Yes, and here is another kit with blue spot free technology:
www.nocrotec.com/shop/product_info.php/l...Dream-Nixie-Uhr.html
Dieter

If you are in a rush, walk slowly!
www.nocrotec.com

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6 years 7 months ago - 6 years 7 months ago #3006 by Jeff
And here is the original IN-18 clock kit with "blue spot free technology" :whistle:

The NixiChron

Regards, Jeff
Last Edit: 6 years 7 months ago by Jeff.

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