[Amps] L7 Question

[Mike Schatzberg]

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