[Amps] Need reliable source for ACOM2000A tubes GU74B?

[MU 4CX250B]

I believe John is correct that all GU74b tetrodes date from the Soviet
era, whether used or NOS. I was fortunate enough to buy a dozen of
them for $360 when demand was still low. I ruined one them by applying
RF without first conditioning the tube. After that experience, I ran
the filaments for  a couple of days and cooked each  tube for several
hours with a 200-300W resting current, but no RF drive. All my spares
then worked fine at full output. I have run three of them in my hb
160/80m amplifier (2800V plate voltage, 340V screen voltage) for
several years and really like the tubes. They are stable and drive to
full output with a few watts. I use a passive 50 ohm attenuator on
their grids to provide a correct resistive match to my Flex xcvr. This
amp and all circuitry  and construction details are shown
on w8zr.net. (Sorry, but I’m keeping the tubes for spares and for
other projects.)
73,
Jim w8zr
Sent from my iPhone

> On Nov 24, 2022, at 10:59 AM, gudguyham--- via Amps <amps at contesting.com> wrote:
>
> There has been some jibberish that the Chinese “might” be making a new version of the Russian GU74B.  I have not seen one yet and I’ll believe it when I see it.  Until then AFAIK all GU74B tubes are all NOS Russian Cold War surplus.  The last batch made probably in the mid 90’s.  Unless these “alleged “ new GU74B tubes are real, any GU74B you buy from regardless who you buy it from, are all NOS if in fact they never been used.  Therefore, if you can find ANY factory sealed GU74B it’s no better than any tube you can buy at any ridiculous price!  A GU74B for $999.00 is the same as you’ll buy for a sealed NOS unit for about $200.00.  Some off shore sellers will sell you these for about $125 each in a moderate bulk lot.  How many can you afford to replace for that price?  4cx800 is an Eimac number and Eimac never made one.  Hams started calling GU74b tubes 4cx800 because if Elmac made them that’s what they would probably call it based on specifications.
>
>
> Sent from the all new AOL app for iOS
>
>
> On Thursday, November 24, 2022, 12:06 PM, john at kk9a.com <john at kk9a.com> wrote:
>
> If you have a perfect antenna/coax system with no mini arcing occurring, the
> Acom 2000A is a fantastic amp.  WOW, $2,000 for new tetrodes!
>
> GL,
> John KK9A
>
>
> John Bodine wrote:
>
> GU-74B is the correct tube and here's a link that I have used with no
> problems-
>
> https://www.dxengineering.com/parts/plb-4cx800a-t
>
> I have bought off of ebay with real horror show results. DX engineering
> used to guarantee their tubes for a year which is a very good thing but
> check to make sure.
>
>> On Wed, Nov 23, 2022 at 1:38 PM <kq2m at kq2m.com> wrote:
>>
>>
>> I need to replace one set of tubes for my ACOM2000A.
>>
>> Can anyone confirm that GU74B is the correct tube?  If not, what is the
>> correct tube?
>>
>> Does anyone know of a reliable source for the ACOM200A good quality
>> tubes?  Approximate cost?
>>
>> Tnx & 73
>>
>> Bob, KQ2M
>
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