[Amps] Gettering the GU-74B

[Kees - pa7two]

Hi Peter, 

I normally start with the following gettering schedule for the GU74B tubes:


1) No HV connected. Fan is connected at all times!
2) 20% of maximum filament voltage for 2 hours.
3) 40% of maximum filament voltage for 2 hours. 
4) 60% of maximum filament voltage for 2 hours.
5) 80% of maximum filament voltage for 2 hours.
6) 95% of maximum filament voltage for 24 hours.
7) 95% of maximum filament voltage & 50% of max HV loaded via a resistor for 4 hours.
8) 95% of maximum filament voltage & about 90% of max HV loaded for 24 hours.
9) Next is QSO-ing at 50% RF level for a few hours carefully observing the tube behavior. After this you can try to push some more RF out of the tube.

If the above is the best approach I am not sure, what I do know that it works for me :-)

Since I do sell some spare GU74B tubes so now & then, I got reports of users who do not do any gettering at all, or just only the filament procedure and put the tube in the amp and next leave it running idle for 24 hours. Very (I mean *very*) rarely I got informed that things went wrong. So, I think I can say that the GU74B tubes are very robust and normally do not arc in general. 

With all tubes, either new or NOS, I ALWAYS advice to perform the getting procedure.


Vy 73, de Kees. 

AmateurRadio : PA7TWO
 - M5TWO Locator: JO22jp. 



> From: dg6man at pjconsult.de
> To: amps at contesting.com
> Date: Mon, 1 Nov 2010 21:36:40 +0100
> Subject: [Amps] Gettering the GU-74B
> 
> Dear Fellows,
> 
> What is the best procedure to getter a NOS GU-74B.
> 
> A befriended OM brought me his fairly new ZZ 750 PA with a failure of
> the Zener diodes for the screen voltage.
> 
> To get this "Kalashnikov" like technology a bit more refined, I will insert
> a G3SEK Tetrode Board.
> 
> But it is also interesting how to get this tube properly gettered, in order to
> avoid arcing to the best possible.
> 
> In a German forum it came to my attention that the GU-74B can be very nasty
> with regard to arcing.
> 
> 
> _____________
> vy 73 de dg6man
> peter
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