Newsgroups: rec.audio.tubes
Subject: More M-O Valve History
Date: 2 May 1997 14:16:08 GMT
Organization: Thorn Microwave Devices Limited
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The following is more histroy regarding M-O Valve and the type of tube
processing they did, both routine and for special military tubes (valves).
This is from Mr. V. Howard Smith, past Technical Director.
**************************************************************
The special "military" valves (I have not used that word for a long time!)
made by MOV were given the designation 'Q' or 'SQ' if I remember correctly,
although many of the specials were military versions only with relatively
conventional type designations or CV numbers.
The vast majority of these tubes, sorry valves, were only made in the
special mil versions. So they were not selected from commercial production,
but specially made to the mil specs.
Commercial valves were made by a different organisation and management, on
floor 'E3' (east wing, 3rd floor). Another group (where I worked 1969 -
1971) known as 'Disc Sealed valves' made the high frequency disc-sealed
tubes (up to 1 GHz) and the special mil types in E4 (East wing 4th floor).
There was a lot of friendly rivalry as you can imagine.
The commercial valves (E3) were pumped on very large rotary machine pumps
with fast indexing speeds, everything geared for high volume and low cost,
they were very good at it too! They hung in to the very last, until most of
the other big guys had given up, and world demand = production capacity
again, then increased the price and were very profitable for years after
the pundits had said that valves were dead. I know that the KT88's were
doing 10,000 hours, and made at 2,000 per month.
In section E4, the special valves were pumped, aged and tested to much
higher standards (usually Mil, or UK equivalent). The disc-sealed tubes
were pumped on multi head (10 head manifold, if I remember correctly) metal
or glass diffusion pumps. Glass were mercury, metal were oil. The 'valves'
(conventional glass with octal bases mainly) were pumped on smaller rotary
machine pumps with low indexing speeds, a cause of much debate with the
commercial valve people! Again the pumps were two and three stage box
pumps, but these were maintained to a very high standard and tested to a
worst pressure of 0.0005 Torr, usually making about 0.0003.
Like in most businesses, the quality actually comes down to the pride
and ability of people. Both E3 and E4 had very good people and they
maintained the quality certainly to my knowledge up to 1984 when I left MOV
(as Technical Director). They were very much of the 'old school', a dying
breed unfortunately (pun not intended). People who joined the sections, but
did not have the 'right' attitude, some how seemed to leave the company
fairly quickly, with the 'right' attitude you could join the 'family'.
MOV was very lucky in having Mr Pat Cundy (rumour has it that he was
seconded to work on the 'black box' flight recorder) as the technical
boffin for valves, he had seen and fixed every possible problem, and
probably several times in his life. Infrequently, as he was a very proud
man, he was supported by Dr R.O. Jenkins ('Jenks') from the MOV "Valve
Research Labs" (VRL) in Wembly. When I joined, E3 was run by Mr Macfarlane
('Mac', nobody ever knew his Christian name), and E4 by Jeff Thorpe. Pat
and Mac used to have furious rows, as can be usual between engineering and
production, whilst they would each defend the other just as furiously in
all other circumstances.
One other interesting feature, occasionally the demand for commercial tubes
would exceed the machine pumps in E3 (or they were down for servicing, the
pump rotating plates had to be reground occasionally and they could be out
of service for several months getting the pressure down to spec), and
commercial tubes were manufactured in E4. Pumped aged and tested. One of
the differences on the Mil valves was the number of times the valves were
ECH'ed, and how the cathodes were activated, this was all automated, and
was difficult to change efficiently.
Thus the pump indexing speeds and processing was maintained to Mil
standards for the commercial tube spill over production. There are thus
some exceedingly good Gold Lion KT88's somewhere out there!!!
From jjense--(at)--irius.com Tue May 6 16:49:42 CDT 1997
Article: 30110 of rec.audio.tubes
From: "John W. Jensen"
Newsgroups: rec.audio.tubes
Subject: M-O Valve (Still More Info)
Date: 6 May 1997 18:16:03 GMT
Organization: Thorn Microwave Devices Limited
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For those who read the previous message and wondered what ECH means, here
is an explanation. In the U.S. tube industry, such a piece of equipment
was often called a 'bomber' meaning that the work inside the vacuum was
being heated by 'rf bombing'.
ECH
Stands for “Eddy Current Heating”. Used to heat up the valve internal
electrodes through the glass envelope to red heat, in order to outgas them,
and even hotter than the bake temperature. It was particularly important
to ‘ECH’ the getters during processing, as getters are made of particularly
active constituents and soak up crap during storage.
The getters were outgassed several times during processing on the pump,
fired just prior to pinch off, and fired again after cathode processing
(about twice normal heater/filament voltage and drawing emission current).
M-O V
Originally “Robertsons Lamps” circa 1890, and made vacuum lamps with
carbonised cotton filaments. When I left M-O V in 1984 you could still see
a picture of a lamp (about 15 feet high) with a pinch off at the top of the
bulb, with Robertson’s Lamps written underneath, on the side of one of the
old original buildings.
Then purchased by a German company called Osmium Wolfram (Wolfram as in
Tungsten) who made gas filled lamps, the name was Anglisised and truncated
to Osram.
This then German company ‘Osram’ was impounded during the first World War
and passed to GEC (which was then mainly an American company I believe?).
The name was changed to Marconi Osram Valves in 1919, and about a year
later to M-O V.
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