[AMPS] CENTURION HELP

Sun, 7 Sep 1997 11:30:09 +0000

> "The purpose of this modification is to turn off the tube bias while in
> standby or receive mode. A few owners who had previous experience with
> amplifiers from other manufacturers, noticed that we biased the tubes in
> standby. Although this caused no performance problems, it was different
> from what they had grown accustomed to."
> 
> The modification was for units manufactured before 3/2/92 and affected
> several series of serial numbers.
> 
> Of note too, is that they changed the bias zener reference diode from a
> 1N756A to a 1N5344B .

I usually avoid general statements, but there might be something to 
be learned here that will help people owning certain amps.

The Centurion amplifier I looked at had NO defective components, but 
sitting on a table just idling away 250 degree C temperature 
indicating paint on the anode seal melted right away after five 
minutes!

On a similar note, the GLA-1000 Dentron and Amp Supply sweep 
tube amp, as well as at least one 3-500Z amp they made, exceed the 
rated CCS dissipation of the sweep tubes and seal temp rating of the 
3-500 tubes on idle. 

The original AL80 amplifier (under S/N 200) did the very SAME thing. 
The bleeder resistors in the AL80 were two watt carbons, dissipating 
2.5 watts CCS!! Some Dentrons have the same or similar problems.

By the way, the "reason" given by the "engineer" for not cutting off 
tubes on standby was something about "not wanting to thermally shock 
the tubes because that causes tube failures". He showed me a 
statement in a certain non-ARRL "Handbook" that actually did say 
that!!!

73, Tom W8JI

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