[Amps] Low power output from 4-400A linear

[Scott Townley]

Numbers according to Eimac in parentheses:


  Measured power out: 855 watts  (1200)
  Power input: 1216 Watts (1980)
  Ep:3200 Volts   (3000)
  Ip: 380 Ma.( at max output)  (660)
  Ig: 250 Ma.            (200)
  Eg: Bias 00            (0)
  Static Ip: 120 Ma.     (140)

PS that would all be with 80 watts drive.

Not an expert, but sounds like the plate impedance is too high.  That would 
give low Ip and high Ig.  According to the datasheet it should be ~2500 
ohms for two in parallel.
Really the question is, what's the screen current?  I would think that even 
in g-g/triode-connected service the screen current is a key indicator.

I don't recall the exact bits but the 850A isn't tapped correctly as-is 
from the factory.  Obviously it will resonate with the right tune-C but the 
Q is way off from what you normally shoot for.



At 07:27 2005-10-11, Bruce Lanning wrote:
>Several years ago, I built a GG amplifier using a pair of 4-400A. The grid
>and screen are grounded at the tube socket.
>
>I feel that the power out is quite low. Below are some of the operating
>parameters:
>  Measured power out: 855 watts
>  Power input: 1216 Watts
>  Ep:3200 Volts
>  Ip: 380 Ma.( at max output)
>  Ig: 250 Ma.
>  Eg: Bias 00
>  Static Ip: 120 Ma.
>
>I am using the B&W Pi-network, model 850A output tuning inductor
>.
>I have checked the tube filament pins for a poor solder joint.
>They both looked OK, but I resoldered them to no avail.
>
>Maybe someone out there could throw some light on my problem, or if I even
>have a problem...
>
>
>
>
>
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