Gary -
Any socket resistance will allow the tube pins to heat up enough for the
solder to melt and run out. It can be prevented by making sure the socket
clips are clean and tight on the tube pins. Their springs can get weak
from past heating.
73 - Don, ve1bn@ns.sympatico.ca
----- Original Message -----
From: "Gary Hoffman" <ghoffman@spacetech.com>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Sent: Sunday, December 11, 2005 11:06 PM
Subject: Re: [TenTec] Centurion
> 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@Blomand.Net>
> To: "Discussion of Ten-Tec Equipment" <tentec@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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>>
>>
>
>
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