[Amps] 3-400Z vs. 4-400A

[Richard]

>>>Some time ago a guy told me he was substituting the
>>>4-400A tube in his Swan Mark 1 amplifier instead of
>>>using the 3-400Z tube.  He had a large supply of the
>>>4-400A tubes on hand and said they were working very
>>>well in the Swan Mark 1 even though it was designed
>>>around the 3-400Z tube.  Is this an ok thing to do in
>>>the long term?
>>>73,
>>In g-g, at 0v bias, the 4-400A needs c. 3400V to idle at the requisite 
>>75mA. 
>
>>-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
>>www.vcnet.com/measures.  
>
>So add some bias already. <g>
>-- 
Adding bias to raise the ZSAC to 75mA/tube with 3000VDC would require 
connecting a 1A, 1 - 3 volt neg. polarity PS to the CT/cathode return. 

-  R. L. Measures, a.k.a. Rich..., 805.386.3734,AG6K, 
www.vcnet.com/measures.  
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