[Johnson] Johnson Valiant 6146 Tube Check

[Richard Knoppow]

      If you mean the plate was glowing yellow you have a problem. The 
6146 is a receiving type tube even though it was designed for mobile 
transmitters. The plates should not glow in normal operation.   Glowing 
plates can mean:
Bias is mis-set
Tube is oscillating because it is not neutralized correctly
Tube is overdriven by a lot.
      Of these the neutralization being off is the most likely 
especially if it happens on the higher bands.
      If the plates glow on your tube tester there is something wrong 
with the tester and its ruining tubes.
      The only tubes that show glowing plates in normal operation are 
fairly high power transmitting tubes with tantalum or zirconium-coated 
plates.  Both should run at about red to yellow heat in order for the 
gas absorption function of the plate material or coating to work.   Only 
very old tubes use tantalum (pre about 1948) but later tubes with 
zirconium coated nickel plates should also be run showing some color 
although they do not need to get as hot as the old ones.   Note that 
many older transmitting tubes have carbon plates which run without 
color.  These are easy to spot because they are _thick_   The 6146 plate 
should NOT show color.


On 7/2/2015 1:39 PM, richard wrote:
> After seeing the 6146 tubes glow  blue last night as I did I checked all 5 today just now & they all check ok and above the 50% in the green on my  Precision Model 920 if anyone knows of it I did notice that 1 of the tubes did glow a bit more on the yellow side than the rest.. So what has me thinking is what caused the Filter Choke by the 3-6146 to get what I think was hot as I just saw it for a second even less tell I shut it down but it was Kinda like looking at a Hot Highway that kind of wave looking heat.. So at this point I will look for the assembly manual ..
> I hope every one has a Great 4th
>     Richard
>
> Richard Morris
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-- 
Richard Knoppow
1oldlens1 at ix.netcom.com
WB6KBL