[TenTec] OT: Need advice checking out a stored 3-500

[Bob McGraw - K4TAX]

I have an Ameritron AL-80B on my desk that I drive with my Omni VII.   It 
does not have a dedicated HV or FIL switch.  When the amp is switched ON, it 
brings up, with delay, the filament voltage and the high voltage along with 
the cooling fan.

I would first check between the tube elements with an ohm meter.  You should 
see a very low R value across the filament pins which are the 2 closest 
together. There are 3 grid pins, all common,  and measuring between each of 
them you should find a very low resistance.  There must be NO resistance 
between the filament and grid pins and NO resistance between the grid pins 
and plate connector on top.  If this checks out OK then proceed as follows. 
If you find resistance between any of the elements, grid to filament, or 
grid to plate,  then you have a suitable lamp base.  Do not put the tube in 
the amp.

First we must presume the amp is working correctly with the present tube. If 
so, then unplug the amp and remove the covers.  Remove the existing tube and 
install the new tube.  Be sure the amp has the correct fuses installed.  Put 
the cover back on the amp and secure to engage the safety interlock . Plug 
in the amp and turn it on.  There is  no need to "burn in" this type of 
tube.   If there is an issue with the tube, it will immediately be obvious. 
You may see a bit of a blue glow inside the envelope but this will go away 
with use.

The with the transceiver and a dummy load start with about 20 watts of drive 
and tune for maximum output.  Then increase drive to about 80 watts and 
touch up the tuning and loading for maximum output.  Do not allow the tube 
to exceed 200 ma of grid current nor 525 ma of plate current.  With key down 
and about 80 watts of drive one should see 1000 to 1200 watts output 
depending on band.  A power output of less than 1000 watts with 80 watts of 
drive indicates a tube that is "soft" or does not have proper emission.

Having the filaments on and no HV serves no purpose.  With drive and proper 
tuning the plate will show color.  The red glow of the tube plate will 
consume any air that has accumulated into the tube envelope.

73
Bob, K4TAX


----- Original Message ----- 
From: "Rodney" <w3krq at dejazzd.com>
To: <wb5jnc at centurytel.net>; "Discussion of Ten-Tec Equipment" 
<tentec at contesting.com>
Sent: Sunday, August 03, 2014 8:10 PM
Subject: Re: [TenTec] OT: Need advice checking out a stored 3-500


> put it in your amp only turn on the filament and let it run for 5 or 6 
> hours until you turn on plate voltage. I know a ham that had 34 304tl 
> tubes and that what he did.
> y
> -----Original Message----- 
> From: Al Gulseth
> Sent: Sunday, August 03, 2014 8:41 PM
> To: TenTec at contesting.com
> Subject: [TenTec] OT: Need advice checking out a stored 3-500
>
> (Posting this for a local fellow ham who currently isn't on the web)
>
> As the subject line says, a local ham friend of mine asked me today about 
> how
> to go about checking out/waking up a 3-500 (Z?) that came as a spare with 
> his
> AL-80A when he bought it a few years back. He's not really sure how long 
> the
> tube had been sitting around unused/un-exercised before he bought the amp.
> I've seen conflicting info on how to go about it, and the last time I had 
> my
> hands on something like that was 30+ years ago when I worked in the 
> broadcast
> industry before I switched to a different career. Any suggestions? Other 
> than
> his amp I don't have any way that I know of to check it.
>
> Contact me off list if appropriate.
>
> BTW Ten-Tec connection: he's driving it with an Orion.
>
> TNX/73, Al
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