[TenTec] Centurion

[Gary Hoffman]

Hmmmm.....and I was just getting around to thinking about building a "test"
socket setup.

Are you saying that filament heat alone was enough to melt the solder ?  I
would have thought that it would take the red hot anode to get it that hot ?

Now as regards running them in the amp to heat them up, this I understand.
However, it takes the anode heat to get a 3-500Z hot enough to activate the
getter anyway, does it not ?  So it seems to me that the only preventative
for a 3-500Z type tube is to heat it often enough that when you do apply the
high voltage, the gas buildup has not been allowed to get so bad that it
causes a failure...right ?   Otherwise, you would have to apply high voltage
gradually, meaning you would have to install temporary resistors in the high
voltage leads, as discussed elsewhere.

If there is yet another way, I don't see it off-hand.

73 de Gary


----- Original Message ----- 
From: "Robert & Linda McGraw K4TAX" <RMcGraw at Blomand.Net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Sunday, December 11, 2005 5:43 PM
Subject: Re: [TenTec] Centurion


> A couple of points and concerns expressed here are thus:
>
> The Centurion when turned on, applies filament voltage and HV at the same
> time.  The opportunity to run the tubes with filament only does not exist
in
> the Centurion.  Same true for most other amplifiers using direct heated
> cathodes and thus instant on tubes.  For those tubes which have a heater
and
> a cathode, that's another chapter in the book and a time delay and warm up
> is required for proper tube operation and life.
>
> As to running tubes outside of the amp, {for what ever reason} as long as
> the filament pins and associated glass seals stay within their temperature
> rating (base seal rating is 200 degrees C max.) then there is no problem.
> However, exceed the temperature rating and the solder may melt out of the
> pins and / or the seals expand such that outside air contaminates the
> envelope.  To that end, I have witnessed a fan failure on a commercial amp
> using 3-500's.  The solder melted out of one of the filament pins and thus
> the tube ceased to function.  These tubes operate at 5.0 volts, +/- 0.25
> volts, nominal, at some 14.6 amps.  Fortunately I was able to re-solder
the
> pin and save the tube.  In order to prevent future failures, an airflow
> switch was installed  in the exhaust to activate the filament transformer
> when adequate airflow existed.  My CCA broadcast transmitter {4 x 4-400's}
> has the same feature.
>
> 73
> Bob, K4TAX
>
>
>
>
>
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