[Amps] Life and gain of 3-500Z

[R L Measures]

On Jul 18, 2006, at 3:12 PM, Peter Voelpel wrote:

> When I recently repaired a TL-922 for a friend the original tubes  
> where
> replaced by RFP 3-500ZG.
> There was no adjustment necessary to the input circuits, if I  
> remember right
> the idling current in SSB Position was 180mA.
> The amp was wired for 240V, fed by 235V, of course run at 50Hz.
> To me the tubes looked pretty hot compared to the QB4/1100 I run in  
> my L4B.
> I measured 1300W out driven at 90W key down.
>
> No idea how it behaves with Eimac tubes as the originals were bad.

What was wrong with them, Peter?
>
> 73
> Peter
>
>
> -----Original Message-----
> From: amps-bounces at contesting.com [mailto:amps- 
> bounces at contesting.com] On
> Behalf Of Phil Clements
>
>>> Lower mu generally indicates higher input impedance, more
>>> negative feedback, and less gain in a g-g amplifier. In a
>>> g-g amp gain is mostly determine by the ratio of load
>>> impedance to driving impedance, and higher mu tubes
>>> generally have a lower cathode drive impedance.
>
> Assuming it is correct that the Chinese tubes are higher mu, and  
> higher gain
> than an Eimac, the zsac would be higher, and the input vswr would  
> change,
> with the same HV and bias voltages applied?
>
> (((73)))
> Phil Clements, K5PC
>
>
>
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R L MEASURES, AG6K. 805-386-3734
r at somis.org