From: jl@glen--canyon.com
On Wed, 31 Dec 2025 00:36:38 +1100, Bill Sloman
wrote:
>On 30/12/2025 2:58 am, john larkin wrote:
>> On Mon, 29 Dec 2025 11:52:28 +0000, liz@poppyrecords.invalid.invalid
>> (Liz Tuddenham) wrote:
>>
>>> john larkin wrote:
>>>
>>>> On Sun, 28 Dec 2025 14:23:50 -0500, bitrex wrote:
>>>>
>>>>> The 6AC10 tube is kind of like 3 12AT7s in the same package, pretty sure
>>>>> everyone has one of those in their junk box..
>>>>>
>>>>> But the transconductance of a triode is wussy, so adding a couple low
>>>>> voltage transistors makes a better regulator than you could get with
>>>>> tubes alone. The PSRR is not too shabby for the parts count, better than
>>>>> you could do with the two other triodes in a traditional diff pair and
>>>>> then you'd want a current source for the pair and bla bla bla.
>>>>>
>>>>>
>>>>>
>>>>> You could use an 0B2 for the Zener for that real vintage feel. And if
>>>>> you stick the optocoupler and transistors underneath the compactron (it
>>>>> gets toasty) your regulator is now also "thermally compensated"!
>>>>
>>>> When transistors were just becoming affordable, there was a last-gasp
>>>> burst of effort to save the tube industry. There were compactrons,
>>>> nuvistors, cold-cathode tubes, tubes that would run at 12 volt B+.
>>>
>>> It was a very long time before the performance of transistors caught up
>>> with Nuvistors. In high radiation and EMP situations, I don't think
>>> they have yet.
>>>
>>> Before transistors began to compete, valves for car radios used +12 on
>>> the anodes but they also used either 0v on the first grids to assist the
>>> electrons out of the cathode or +12v to drag them out.
>>>
>>> In outer space, where the vacuum is 'perfect' and solar radiation could
>>> be directed onto a sheet cathode, new types of valve might begin to make
>>> sense.
>>
>> Philo Farnsworth was a cool guy. He invented the image dissector tube,
>> the Farnsworth Fusor, and did some interesting multipactor work.
>>
>> The perfect vacuum in space has some hazards to power RF circuits that
>> you don't get here.
>>
>> I think he invented the microchannel plate too.
>
>Seems unlikely.
>
>https://apps.dtic.mil/sti/tr/pdf/ADA195556.pdf
>
>"The concept of a continous channel electron multiplier was developed
>near the end of 1950. The invention was that of G.W. Goodrich of the
>Research Laboratories Division, Bendix Corporation."
>
>The original application was for night vision googles. Cambridge
>Instruments used them as electron multipliers in their electron beam
>microfabricators. They had to be replaced every six months, but that was
>tolerable with a million dollar machine.
This is what google says:
AI Overview
The concept of the continuous channel electron multiplier, or
continuous dynode, was first proposed by American physicist
Philo T. Farnsworth in 1930, with early prototypes and active
development occurring in the 1960s, particularly with work by Russian
scientists like I. Pesyatsky and later commercialized into
microchannel plates (MCPs).
Key Contributions:
Philo T. Farnsworth (1930s): Proposed the fundamental idea of
using a continuous, hollow resistor coated with secondary-emissive
material to amplify electrons.
I. Pesyatsky (1940s): Created one of the first working prototypes
of the microchannel plate (MCP) structure.
1960s Development: Significant technological advancements by
various groups led to the modern microchannel plate, a matrix of these
continuous dynode channels, as described in this University of Chicago
PDF and this ScienceDirect article
Philo also achieved nuclear fusion around 1965.
https://en.wikipedia.org/wiki/Fusor#History
John Larkin
Highland Tech Glen Canyon Design Center
Lunatic Fringe Electronics
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