[Amps] Life and gain of 3-500Z

Peter Voelpel df3kv at t-online.de
Tue Jul 18 18:12:14 EDT 2006


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.

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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