Many years ago I got as part of a trade a single 3-500z home brew
amplifier that the builder said just would not produce much output.
I connected my HV supply and could not get more than 250 W or so output. I then
measured the filament voltage at the tube socket and found it to be quite low.
The builder did not account for the filament choke drop. I added a boost
transformer in the primary of the filament supply. It worked well after that.
The boost transformer was small since it only had to add about 15% more voltage
to the primary of the transformer.
73
Bill wa4lav
________________________________
From: Amps <amps-bounces@contesting.com> on behalf of Stan Gammons via Amps
<amps@contesting.com>
Sent: Friday, August 20, 2021 10:44 PM
To: amps@contesting.com <amps@contesting.com>
Subject: Re: [Amps] 572B/T160L tube class C
CAUTION: External Sender
Hi Alek,
I agree on the Dentron amps filament voltage. It is a bit more than 6.3
volts with 220/240 volt mains. No experience with Yaesu and Ameritron. I
can't find it now, but there is/was a document on the RF Parts website
about using a given size and length of teflon insulated wired in the
filament to reduce the voltage. Guess the American made tubes were a
bit more tolerant on filament voltage.
73
Stan
KM4HQE
On 8/20/21 9:08 PM, Alek Petkovic wrote:
> Over the years, I've imported around 200 572Bs from China.
>
> They are definitely not as good as the US ones but they have proven to
> be very serviceable, when treated right.
>
> The single biggest proviso that I drummed into everybody that I ever
> sold them to is to make absolutely certain that the filament voltage
> stays at 6.3V. The Chinese tubes fail very quickly with filament
> voltages of around 7V+, which are the rule in both Yaesu, Ameritron and
> Dentron amplifiers when connected to Australian 240V+ mains voltages.
>
> It is a very simple thing to add appropriate resistance to the filament
> circuit to bring the voltage back to 6.3V. I've modified very many amps
> in this way for many hams. The result has been that all those amps are
> running happily on Chinese tubes, which are lasting many years.
>
> 73, Alek, VK6APK.
>
>
> On 21/08/2021 8:00 am, Stan Gammons via Amps wrote:
>> I agree. I've had so so luck with the Chinese ones. They are nowhere
>> near the quality of the American made tubes. When America made lots of
>> tubes; I think we made the best tubes in the world. But, I'm a bit biased :)
>>
>> 73
>>
>> Stan
>> KM4HQE
>>
>>
>> On 8/20/21 6:52 PM, Carl wrote:
>>> The Chinesw 572B and 811 (it is NOT a real 811A, not even close) are mostly
>>> all junk looking for a trash can. They sometimes let a good one sneak thru.
>>>
>>> Best bet is to pay the freight for a real NOS Cetron or United Electronics,
>>> the only USA real manufacturer who private labeled them for others.
>>>
>>>
>>>
>>>
>>> ----- Original Message -----
>>> From: "Jeff Blaine" <KeepWalking188@ac0c.com>
>>> To: <amps@contesting.com>
>>> Sent: Thursday, August 19, 2021 10:33 PM
>>> Subject: Re: [Amps] 572B/T160L tube class C
>>>
>>>
>>>> How much service do you expect from a new set of tubes? It's one thing to
>>>> know "it can do it, if I want" - but then not actually need the
>>>> capability. It's another thing if you are saying "I want to run a 572b
>>>> 24/7 at full output."
>>>>
>>>> About 10 years ago I was working on a SB200 which was initially setup to
>>>> run RTTY. I did quite a lot of profiling of those using the Chinese tubes
>>>> of the era. Watching very carefully to respect the Pd max of the tubes, I
>>>> found a typical 25% drop in Po over about 100 hours of testing. The
>>>> testing was typically 3-15 minutes key down 100% carrier per interval.
>>>> Plus on-band rag chew, contesting & DX (this was pre FT8).
>>>>
>>>> Carl is about a million times more experienced than I am but I think maybe
>>>> the Pd spec vs. actual was a bit optimistic for the Chinese tubes I had
>>>> because this drop off seemed excessive. However my abuse of those tubes,
>>>> compared to typical ham use, was really bad. Also the SB200 positions the
>>>> tube horizontally which may be a factor as is the generally poor
>>>> circulation even with my augmented cooling.
>>>>
>>>> In the end, I abandoned the 572b and went with the GI7T which was an
>>>> excellent performer by comparison although it required quite a lot of
>>>> changes to the SB200. Unless there is a specific reason to use the 572b,
>>>> if I were building a high duty cycle amp in the future, I would probably
>>>> want to use a metal/ceramic type tube instead of a glass one.
>>>>
>>>> Good luck!
>>>>
>>>> 73/jeff/ac0c
>>>> alpha-charlie-zero-charlie
>>>> https://nam04.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.ac0c.com%2F&data=04%7C01%7Cwlfuqu00%40uky.edu%7Cfa1853348ae14cd8a36408d9644dac66%7C2b30530b69b64457b818481cb53d42ae%7C0%7C0%7C637651107040372700%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=5ZoaGRVcTtsA0iAQFYePPcoeWlZHWF6zjGKimOn4YyU%3D&reserved=0
>>>>
>>>>
>>>> On 8/19/21 8:50 PM, Carl wrote:
>>>>> That tube was designed for AM BCB service by Taylor but didnt catch on
>>>>> there or for AM hams as the T-160L in the late 50's.
>>>>>
>>>>> It was later bought by and designated the 572/T-160L for Unitrd
>>>>> Electronics alone.
>>>>> They couldnt keep up with demand and sold production rights to Cetron who
>>>>> had a much larger production facility.
>>>>>
>>>>> UE then became the 572A and Cetron the 572B. The step top (shouldered)
>>>>> glass was Cetron and the round top was UE.
>>>>>
>>>>> At some point the T-160L was dropped for both.
>>>>>
>>>>> You may also find a 572B with the round top and the Cetron name, those
>>>>> were built by UE as the demand was even too much for Cetron alone at
>>>>> times....such as the SB-200 and the Clipperton L.
>>>>>
>>>>> I have examples of both (no Taylor T-160L) as well as other versions
>>>>> including OEM named such as Dentron, Waters, plus Raytheon, GE, and
>>>>> several others who did not build their own. The top shape ID's the
>>>>> source.
>>>>>
>>>>> I cant remember ever seeing an actual T-160L spect sheet or the tube.
>>>>>
>>>>> Carl
>>>>> Ham since 1955
>>>>>
>>>>>
>>>>> ----- Original Message ----- From: "Fuqua, William L." <wlfuqu00@uky.edu>
>>>>> To: <amps@contesting.com>
>>>>> Sent: Thursday, August 19, 2021 8:56 PM
>>>>> Subject: [Amps] 572B/T160L tube class C
>>>>>
>>>>>
>>>>>> I am looking for full power data for the 572B/T160L operating ICAS
>>>>>> class-c CW and AM.
>>>>>> The only thing I have found thus far is in an ARRL handbook, but it is
>>>>>> obviously the 811A specs.
>>>>>> Not the full 160W plate dissipation specs.
>>>>>>
>>>>>> 73
>>>>>> Bill wa4lav
>>>>>>
>>>>>> _______________________________________________
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>>>>> ---
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>>>>
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