That is very interesting that you are not using a SMPS and still having the 
trouble.  I have never tried the tubes with a  full bridge only a half, I 
wonder if the difference between 50Hz and 100Hz makes any difference, I 
cant see why it would.

You say you have a large reservoir cap, effectively giving you smooth DC.  
I dont think these tubes like smooth DC hence the SMPS being trouble. Try 
removing the cap and see what happens.

Hope this helps,

Tim  



On Saturday, 5 January 2013 14:30:38 UTC, Alex wrote:
>
> Cheers for the replies guys, I suspect that with a bit of running in most 
> of the tubes I have labeled "Slight poisoning" will come right... It is 
> strange that your purple topped tubes are distinctly different from white 
> topped, maybe I got lucky with my white topped but I defiantly prefer the 
> true neon IN-9 glow...
>
> My test rig could not be better for the tubes:
>
> UK Mains -> Isolating TX -> Variac -> Full Bridge -> Large reservoir cap 
> -> 25K W/W Pot -> 1K 10W Fixed R -> mA Meter -> Tube.
>
> Defiantly no switching noise!
>
> I will leave a few of the worst offenders on burn in for a half day and 
> see if they wake up a bit better....
>
> - Alex
>
>
> On Saturday, 5 January 2013 11:46:34 UTC, Tim wrote:
>>
>>
>> Hi Alex,
>>
>> First things first, I love IN-9 tubes and am in the process of making an 
>> audio spectrum analyser with them.  I have both the orange and violet 
>> versions.  My violet ones having the purple top and do illuminate with a 
>> very purple glow :o)  These tubes are trouble and very hard to make them 
>> consistently illuminate from the bottom as they do not have the extra 
>> electrode the IN-13s have.  But there is a way!
>>
>> I would be very surprised if your problem is being caused by cathode 
>> poisoning, it is more likely to be because of the power supply you are 
>> using.  These tubes do not like being run off nice clean DC from a SMPS. 
>> One must consider that when these tube were first being used (decades 
>> before I was alive) SMPS were not used to any extent (if at all?).  They 
>> were powering the tubes from good old half wave rectified DC.  I personally 
>> power the tubes from a mains isolation transformer (I think it came out of 
>> a bathroom shaver socket) and a single 1N4007 rectifier diode.  I don't 
>> think I have ever had one misbehave being powered in this way.  Give it a 
>> go and see if this solves your problems.  
>>
>> Don't forget that the IN-9 are very power hungry compared with that of 
>> the IN-13.
>>
>> Hope this helps,
>>
>> Tim
>>
>

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