Mike,
The simple answer is that there are too many variables to say with any
possible level of accuracy. Eventually that heater will stop boiling off
electrons and the output will drop. But that could be thousands of
operation hours later. It all depends on the specific tube and the
operating parameters. None of which will be consistently forecastable in
any real sense.
Perhaps a more useful question would be - should I leave my amp powered on
24/7 or cycle the power when operating. I suspect the proper answer here
(from a life perspective) is to leave it running - but over time, the
amount of electricity that thing will consume comes into play so that the
issue is less of an operational issue than an economic one.
I think Mike is also right. It's a very long time, as long as you respect
the grid current and plate dissipation limits. The AL has pretty good input
protection circuitry so you are likely covered there. And unless you are
trying to smack 2500W out the back on 10M (higher bands tend to have lower
efficiency hence the plate disipation rises), you probably are not going to
come anywhere the plate disipation limit.
Here we have no even considered the duty cycle of operation and how that
ties into the plate disipation limit.
The 4 hour answer may sound like a smart-ass answer. But that is the only
truthful answer anyone is going to be able to give you.
73/jeff/ac0c
--------------------------------------------------
From: "Gary Patterson" <gpatterson53@hotmail.com>
Sent: Friday, September 25, 2009 4:11 PM
To: <amps@contesting.com>
Subject: Re: [Amps] Dimished Tube Life
>
> "What a Crap answer" ...... What a thoughless response. Clearly, with
> the data given, as we take the limit of N with respect to tube usage the
> answer of 4 converges as the only logical answer.
>
>
>
>> From: noddy1211@sbcglobal.net
>> To: amps@contesting.com
>> Date: Thu, 24 Sep 2009 21:20:29 -0700
>> Subject: Re: [Amps] Dimished Tube Life
>>
>> What a Crap answer, in reality nothing that you could even measure, don't
>> even worry about it
>>
>> Mike
>>
>> -----Original Message-----
>> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On
>> Behalf Of Gary Patterson
>> Sent: Thursday, September 24, 2009 8:02 PM
>> To: amps@contesting.com
>> Subject: Re: [Amps] Dimished Tube Life
>>
>>
>> 4 hours
>>
>> > From: mhughes149@verizon.net
>> > To: amps@contesting.com
>> > Date: Thu, 24 Sep 2009 22:43:13 -0400
>> > Subject: [Amps] Dimished Tube Life
>> >
>> > Hello all !
>> >
>> > I wonder, and I hope someone can offer a reasonable explanation. If I
>> > turn
>> on my AL 1500 Amplifier, which uses the 8877 indirectly heated cathode
>> tube
>> when I come into the shack and then 4 hours later, I turn off the
>> amplifier
>> and go about my business, how much have I shortened that tubes' life ?
>> >
>> > KE9AG
>> >
>> > Mike..
>> > _______________________________________________
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>> > Amps@contesting.com
>> > http://lists.contesting.com/mailman/listinfo/amps
>>
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