On Jun 26, 2006, at 7:28 AM, Mike Clarson wrote:
> But the 8122 was an RCA Tube, so its easy to see how an Eimac
> recommendation
> would get overlooked.--Mike, WV2ZOW
Eimac also manufactured the 8122, which was similar to the Eimac 8930
as far as screen potential. anode potential and anode dissipation
go. The 8930 was basically a 4cx250R / 7580 with a larger cooler.
The Eimac recommended screen shunt-regulator worked ideally with all
of these tubes since it protected the frangible screen from operator
error, loss of anode potential, as well as reverse screen-current.--
note - the shunt regulator operated from the current through the HV
bleeder R, so it was inherently current-limiting --- baring a
lightning strike.
For < 600 screen V tetrodes, the circuit is brilliantly simple
and virtually foolproof.
cheerz, Mike
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-
> bounces@contesting.com] On
> Behalf Of R L Measures
> Sent: Friday, June 23, 2006 7:31 PM
> To: m.ford
> Cc: amps@contesting.com
> Subject: Re: [Amps] RCA 8122 Tubes
>
>
> On Jun 23, 2006, at 3:49 PM, m.ford wrote:
>
>>
>> ----- Original Message ----- From: "R L Measures" <r@somis.org>
>> To: "Glenn McNeil" <vk4tzl@bigpond.net.au>
>> Cc: <amps@contesting.com>
>> Sent: Thursday, June 08, 2006 9:09 AM
>> Subject: Re: [Amps] RCA 8122 Tubes
>>
>>
>>> On Jun 8, 2006, at 1:55 AM, Glenn McNeil wrote:
>>>> Hello Gang,
>>>>
>>>> I've just been given a pair of RCA 8122 Tubes...never used,
>>>> still in the
>>>> original boxes. Date code 69-04.
>>>>
>>>> What are the chances they are still OK for use ?
>>> Very good if the Al-Ox ceramic has a purplish color from added
>>> manganese. A high-potential tester will give the answer is
>>> seconds. With 5kV between the anode and screen, there should be
>>> less than 5uA of leakage. i would not uses these tubes in a
>>> unmodified NCL-2000.
>>
>> The best modification for the NCL-2000 is to change the way the
>> operator abuses it.
>> Keep the meter in screen current and watch it all the time. I'll
>> bet it was all the gg guys that got
>> caught looking at the grid current that gave the amp a bad name.
>
> Not using the Eimac-recommended current-limiting screen shunt
> regulator circuit for small tetrodes gave the NCL-2000 its reputation.
>>
>> Mike k1ern
>>
>>
>>
>>>>
>>>> Any ideas
>>>>
>>>> 73
>>>>
>>>> Glenn
>>>> VK4TZL
>>>>
>>>> _______________________________________________
>>>> Amps mailing list
>>>> Amps@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/amps
>>>>
>>> R L MEASURES, AG6K. 805-386-3734
>>> r@somis.org
>>> _______________________________________________
>>
>>
>
> R L MEASURES, AG6K. 805-386-3734
> r@somis.org
>
>
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
>
R L MEASURES, AG6K. 805-386-3734
r@somis.org
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|