[R-390] Tube longevity

[Mark Huss]

Time for my two cents.  (1) is best, though with mil-spec tubes, heater 
failure from start-up current is rare, or so the old manuals said.  (2) 
the Stand-By position turns off the B+, but is very bad if you have done 
a solid-state mod to the Power supply rectifiers.  If you do not have 
the 26Z5 tubes in the power supply, turning off the plate voltage by 
switching to stand-by will cause the plate voltage to raise excessively, 
and can cause some caps to blow.  Never use stand-by.  Probably the best 
thing to do is to add a CL-80 surge suppressor in series with the 2 Amp 
fuse in back.  Personally, I don't think tube life is reduced 
significantly by turning the receiver on and off.  I suppose you will 
get a few hundred hours more from a tube that is about to loose it's 
heater if you leave it on continuously.  The exception is the Ballast 
Tube.  That is rated in cycles (about 2000-5000).  On-Off cycles will 
definitely affect the life of that tube.

g kwitka wrote:

>To prolong tube longevity which is better:
>1) keep the set on with the volume and rf gain turned
>down
>@0 Install a B+ switch and keep the palte voltage off
>with the heaters on until the set is used?
>Thanks
>
>
>
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