[Amps] Question about glowing 3-400z's

[Scott Townley]

I would say that, considering the idle plate dissipation is 260W/tube, that 
some color would be expected.


At 19:25 2006-07-09, w2cqm at juno.com wrote:
>I'm working for the first time on a pair of 3-400Z's in a Swan Mark I. On 
>both the high and low power position,   the amp is making exactly the 
>instruction  manual's specified idle current. Plate voltage is 2900VDC and 
>idle current is 180ma.  With key down and no excitation at this 
>level,  the tubes begin to glow  to a  color that  I consider to be a 
>bright red. The plate current meter shows no rise in current draw during 
>this entire  process.   The amplifier loads perfectly and when driven with 
>100w ,  power output is about 1100W. The question is whether this 
>"glowing"  is the normal characteristic of a  pair of  Eimac tubes?? Any 
>comments will be appreciated. Ron W2CQM/3
>
>
>
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