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Re: [Amps] L7 Question

To: <amps@contesting.com>
Subject: Re: [Amps] L7 Question
From: "Mike Schatzberg" <cherokeehillfarm@earthlink.net>
Date: Tue, 26 Apr 2005 11:25:02 -0400
List-post: <mailto:amps@contesting.com>
Hello Fernando:

Of course your amp has instant heating triodes, which only require a few 
seconds to come up to temperature.

If your amp does not have inrush protection, it is a good idea to turn it on, 
with the low voltage option engaged, rather than the higher voltage SSB option. 
 This will control the inrush current to a safer level.  There are outboard 
devices, as well as onboard modifications which can further limit inrush 
current, to protect all of your amps components.

The life of your triodes is probably more related to the filament voltage your 
Drake uses, rather than to the conservative level of operation you place upon 
it.  Some of the amplifiers seem to run voltages above even 5 Volts, which will 
shorten the life of the tubes dramatically, without providing much benefit.  
Ideally, the voltage may be as low as 4.85 volts, to greatly extend the useful 
life of the tubes.  

There are various articles published which can help you to modify the filament 
voltage to this lower level.  

One other simple thing to do, is always allow the tubes to cool down following 
transmitting, meaning leaving the fan running for several minutes following 
your last transmission.

Lastly, your tuning techniques, and limiting the strain upon the finals during 
tuning is important as well.  Tuning methods using a string of higher speed CW 
dits, 35 wpm for example, will limit the strain on all amplifier components 
while tuning.

The triodes you are using are really rugged, and the newer graphite anode 
versions dissipate even more power.  With care, they could last a lifetime.

Regards,

Mike Schatzberg 
WB2AJI  
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