[Top] [All Lists]

[Amps] Dual 8877 Alpha 77S final query

To: <>
Subject: [Amps] Dual 8877 Alpha 77S final query
From: w2cqm at (
Date: Mon Jul 28 22:26:07 2003
Many thanks to all those who offered input in response to my query about
the merits of adding the second  tube to the Alpha 77S type amplifier.
The thoughts were insightful and the general consensus was that the
effort was worthwhile.  In the planned project, I'll be using the
Ameritron series amplifier as the base for the project. Only one concern 
remains. On all the 8877 retrofits I've done, I always used a discrete
filament transformer in the circuit. I was able to fire up the filaments
and cooling fan and after the mandated  3 minute delay, I'd step start
the plate transformer and away I went. In the current project, I'll be
using the Peter Dahl replacement 77S transformer with the whole range of
filament and accessory secondary windings off the single primary. The
question is :

        a. is it permissable to apply high voltage simultaneously to the
filaments and plate and wait the delay time before      applying excitation?
Eimac data sheet just mentions "cathode warm up time 180 seconds). 

        b. does it make good sense to place a vacuum (or a good quality )  relay
series installed  in one leg of the high        voltage AC secondary and let
that switch in the HV  to the rectifier board after the delay?  

Thanks, Ron W2CQM/3 

<Prev in Thread] Current Thread [Next in Thread>