[Drake] 3-500Z red by itself???

[Garey Barrell]

Dave -

There was a considerable discussion on this topic on the DrakeRadio group on Yahoo.

It's quite possible that your 3-500Z can be 'repaired'.

These tubes are intended to RUN at red heat, and considerably less life is obtained by running 
them 'black'.

EIMAC 3-500Z tubes have a coating on the plate that acts as a 'getter' to adsorb gas molecules 
when heated to red heat.  The trick is to keep it at red heat for a 'period' without damaging 
either the tube or the power supply.   There are several methods to accomplish this in the 
discussion.

Also a MUCH more active group with over 1200 members.

<http://groups.yahoo.com/group/DrakeRadio/>

73, Garey - K4OAH
Glen Allen, VA

Drake 2-B, 2-C/2-NT, 4-A, 4-B, C-Line
and TR-4/C Service Supplement CDs
<www.k4oah.com>

Dave Edwards wrote:
> Several months ago, my Drake L75 had an issue where as soon as I transmit, the .5 ohm (or 
> whatever it is) protection resistor would go POW.
>
> I had another 3-500Z tube that has been sitting on a shelf for probably 15 years!!  (condition 
> unknown)
>
> Tried it, and problem solved. Full output, no fireworks!
>
> I tried the amp yesterday, full output, but after 5 minutes or so...even on receive...the grid 
> current meter would go negative, and after a minute or so, the tube would slowly turn 
> cherry-red, the fan goes to high speed.  So I shut it off.
>
> Turn on again after several minutes...same scenario.
>
> Time for a new tube from this century????
>
> Thanks for your thoughts!
>
> By the way...awful quiet list lately!
>
> ....Dave