[neonixie-l] Re: Weird spot on XN-11 Anode

[Roddy Scott]

That was my first thought that the tube was connected wrong but as XN-11 
pins run 1 to 0 instead of 0-9 and the circuit board is dedicated to them I 
was extremely careful to make sure it was aligned properly by even 
illuminating the stand tube before soldering to check all wires were 
correctly lined up to their relevant hole. It has been checked on another 2 
QTC boards one of which is running GNP-7AH tubes and shows the same 
symptoms so it is a case of "He's dead, Jim!"

A power supply is high on my list of wants just now as on board testing is 
not the best way.

The close up shows the white spot on the mesh as well as several blue areas 
behind the mesh.




This is the XN-11 board configuration from Pete's QTC PDF





The pinouts of the XN-11 as opposed to those on an IN-8-2 which is 0 to 9.







On Saturday, July 1, 2017 at 1:46:19 PM UTC+1, Paul Andrews wrote:
>
> Never on the mesh (yet), but I did see something similar when I had one of 
> the numerals wired as the anode rather than the actual anode (in my 
> defense, the actual anode pin was missing).
>
> I would check that it is wired correctly, including possible shorts. Then 
> check it on a different QTC mother board to see if it is the motherboard. 
> Then check a different type of tube on the original motherboard to see if 
> you get the same effect (another check of the motherboard).
>
> I also don't have a bench supply - it is on my list - but in the meantime, 
> I use a NCH Nixie power supply and a breadboard. The power supply is rock 
> solid and the voltage is easily adjustable.
>
> Good luck. 
>
>

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[neonixie-l] Re: Weird spot on XN-11 Anode

[GastonP]

If the mesh glows (as this one seems to be doing) then suspect that there 
is AC instead of DV applied.
The mesh can't glow when the right potentials are applied, whichever the 
value of the current through it is.

Gastón

On Friday, June 30, 2017 at 8:11:55 PM UTC-3, Roddy Scott wrote:
>
> I don't have a power supply but the spot occurs on the mesh and with a 
> different digit  there is a a different spot. The tubes were NOS and I have 
> had them lying about for over a year in a box. I have a couple of QTC 
> boards so I am going to try them on those boards to see if they are the 
> same.
>
> I have never seen anything appear on the Anode mesh with any tubes that I 
> have used so far so this is totally new to me.
>
>
> On Friday, June 30, 2017 at 9:50:36 PM UTC+1, gregebert wrote:
>>
>> How do things look when you bench-test the tube on a DC supply ?
>>
>> Is the spot actually on the anode mesh itself ? Ionization occurs at the 
>> cathode, so this is indeed strange.
>>
>>

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[neonixie-l] Re: Weird spot on XN-11 Anode

[Paul Andrews]

Never on the mesh (yet), but I did see something similar when I had one of the 
numerals wired as the anode rather than the actual anode (in my defense, the 
actual anode pin was missing).

I would check that it is wired correctly, including possible shorts. Then check 
it on a different QTC mother board to see if it is the motherboard. Then check 
a different type of tube on the original motherboard to see if you get the same 
effect (another check of the motherboard).

I also don't have a bench supply - it is on my list - but in the meantime, I 
use a NCH Nixie power supply and a breadboard. The power supply is rock solid 
and the voltage is easily adjustable.

Good luck. 

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[neonixie-l] Re: Weird spot on XN-11 Anode

[Dekatron42]

I believe that it is the same symptom as the "blue dot" effect in Nixies, 
you can read about "The Infamous “Blue Dot”:" a bit down on Michael 
Moorrees webpage: https://threeneurons.wordpress.com/nixie-power-supply/ . 
I've seen both orange and blue dots on several Nixies. I recently had 
orange dots with some Z560M nixies and the fix in that clock design was to 
use resistors across all cathodes and a voltage divider from anode to 
cathode to set the voltage to a suitable level - check the "Lower Voltage 
Cathode Drivers:" on the same webpage to see the effect of these "mid-pull" 
resistors.

/Martin

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