I don't really know what they use either, which is annoying.
"People say" it's on the cathode, which certainly would be convenient.
LY1DQ's datasheet says the tube is indirectly heated, which makes it at
least likely for that to be true.
In any case, finishing my HiPot tester would seem to have good long-term
value. My daughter is home from college for spring break, but she
doesn't seem interested, for some reason...
73
Jim N7CXI
On 3/12/2012 7:14 AM, Carl wrote:
> American external anode tubes with indirectly heated cathodes are
> rejuevenated by running filaments only for a day or two in extreme
> cases. These are 8874, 3CX800, 8877, 4CX1000A, etc
>
> Directly heated tubes have the gettering material on the inside of the
> anode surface and require running at rated power on a regular basis. The
> alternative is the same as glass tubes....run reduced plate voltage and
> more positive bias to reach a high enough dissipation to activate the
> getter. These are 3CX1000, 3CX1200, 3CX3000, 4CX5000, etc.
>
> Ive no idea what the Russians use for gettering and dont want to make a
> WAG....
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Jim Barber" <audioguy@q.com>
> To: <Amps@contesting.com>
> Sent: Monday, March 12, 2012 2:47 AM
> Subject: [Amps] Gettering GU-74B's in-place with screen voltage?
>
>
>> Is there any reason I shouldn't getter a set of GU-74B's in-place in the
>> amp with blower air, filaments hot, and with grid and screen bias
>> applied, but with the plate caps lifted? The amp in question is a QRO
>> HF2500DX that appears to be virtually unused, but also appears to have
>> been stored for an unknown amount of time.
>>
>> Most of my experience is with metal-ceramic triodes (which "bang" after
>> storage without gettering) and good-old beam pentodes like the 813,
>> which don't, or at least haven't yet for me, at least. These (Russian)
>> metal-ceramic tetrodes are undiscovered country, so I may be being
>> over-cautious. Or not?
>>
>> Thanks,
>> Jim N7CXI
>> _______________________________________________
>> Amps mailing list
>> Amps@contesting.com
>> http://lists.contesting.com/mailman/listinfo/amps
>>
>>
>> -----
>> No virus found in this message.
>> Checked by AVG - www.avg.com
>> Version: 10.0.1424 / Virus Database: 2113/4866 - Release Date: 03/12/12
>>
>
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|