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Information - Help 
ID = 14974
Great Britain (UK)
Brand: MO Valve Co. Ltd.; GB
Tube type:  Double Diode-Triode   Audio Frequency 
Identical to VR101 = 10E/280 = CV1101 = MHLD6

Base Octal (Int.Octal, IO) K8A, USA 1935 (Codex=Uf)
Filament Vf 6.3 Volts / If 0.65 Ampere / Indirect / Parallel, (AC/DC)
Description Earlier name for CV1101, also known as 10E/280. Protype was MHLD6. Typ Gm=3mA/V at Ia= 11mA. 
Tube prices 1 Tube prices (visible for members only)
Information source Taschenbuch zum Röhren-Codex 1948/49   
-- Original-techn. papers.   
VR101: Collection JR
Jacob Roschy

VR101: rtt
Michael Schlör


Usage in Models 1= 1940 ; 1= 1941?? ; 1= 1942?? ; 1= 1950??

Quantity of Models at with this tube (valve, valves, valvola, valvole, válvula, lampe):4

Forum contributions about this tube
Threads: 1 | Posts: 8
Hits: 2193     Replies: 7
VR101 (VR101)
John Turrill

Dear Radio Friends,
                              just a few words about this seemingly quite 
ordinary octal based double-diode-triode, developed by Marconi-
Osram in U/K, seemingly just prior to WW2, mainly for military
use,- indeed, the only application I'm aware of was as audio o/p,
plus a second one as B.F.O., in the well known R1155 receiver
used by the R.A.F. for many purposes during (and after) that war.

Further investigation reveals, however, that this valve appears to
have no direct equivalent, and was basically known as the type
MHLD6, later given the R.A.F. no. VR101 & later CV1101.
The only characteristics I've discovered (official Air Ministry) are -

Anode volts ------200v.                 Diode 1 test 0.8 mA.
Anode current----11.5 mA.            Diode 2 test 3.5 mA.
Grid bias --------- -5v.
Heater ----------- 6.3v. @ 0.65A.

The triode appears to be low impedance, and for some reason one
diode bigger than the other; if anyone has more complete figures
or facts about this valve I'd be grateful to see them.

Regards,  John Turrill.

Jeremy Harmer
  2 One other bit of information in the EVS sheet for this valve is "Diode 1 shall be the diode remote fromthe triode section" - but no indication as to why. I guess diode 1 has different characteristics due to its different proximity to the other electrode structures.

Hans-Thomas Schmidt
  3 Hi John,

I dont have some characteristics to the VR101/CV1001.

But I have short datas from the MHLD6:

MOV, amplifier triode withs two diodes. common cathode.
Octal: shield, f, p, diode1, diode2, nc., f, c. Cap = grid

filament: 6,3V and 0,65 mA
plate: 200V and 3,8 mA
Grid: -3V
Ra: 18200 Ohms
gm: 2,2 mA/V
amplification factor: 40
cathode resistance: 800 Ohms

From the diodes there are no datas listed.

Source: Babani, International radio tube encyclopedia, last edition 1958, 1. supplement

Best regards, Hans-Thomas
John Turrill
  4 Dear Hans-Thomas,
                               many thanks for your help, in actual fact, I
should have mentioned I had seen the data in the Babani book,
but the figures don't seem to make sense!
I know the figures I quoted to be correct,- that is, 200v. on the
anode with -5v. bias gives 11.5mA anode current & 3mA/v. - as 
this is from an official R.A.F. data sheet; sounds like the same one
Jeremy has, and thanks for that also Jeremy. (if you've looked down
inside the valve - difficult!-, you can just see the 1st. diode, with
the second, smaller one just below that).

As if to prove a point, testing a new valve at -3v. bias yields an 
anode current of about 25mA, so I have to assume Babani isn't 
correct (unusually). 
I've searched the web and all the books I can find, but I'm
beginning to wonder if there is any further information!

Thanks, John.
Hans-Thomas Schmidt
  5 Hello John,

here are another datas from the MHLD6 from Osram:

Triode, duodiode

Octal: nc., f, d1, d2, p, nc., f, k

filament: 6,3 V and 0,65 mA
plate: 250 V and 11,5 mA
gm: 3 mA/V

from Prehled Elektronek, 1954

VR101 = MHLD6
octal same like in my first post
f: 6,3 V and 0,65 mA
p: 200 V and 11 mA
g: -5 V

from Röhrencodex 1951

Best regards, Hans-Thomas
John Turrill
  6 Dear Hans-Thomas, 
                            thanks again for this information, which seems
to confirm all my previous data, and that, in this, the Babani is
surely wrong.   I find this a little worrying,- makes you wonder if
any other data is wrong, too, in those books - though mostly you
can cross-check with other sources, so far I've not found any
other doubtful figures. 
As you mention Osram, am I right in thinking this is an original
German firm? - and if so, I'm wondering how and in what way they
came to be associated with the British Marconi firm?

Regards, John.
Hans-Thomas Schmidt
  7 Hi John,

the blue Babani book is one of the best I had ever seen. But it is very difficult to get them. My issue I have found it in Canada and it was not cheap. I have seen it firstly in the library of the Deutsches Museum in munich and it is a must for tube collectors.

The Osram was a light bulb manufacture leaded by Siemens. At beginning of the last century they produced bulbs in several countries, so eg. in England. Osram started at 1906. The name is a abbreviation from Osmium and Wolfram (tungsten), two important metals for bulb manufacturing. In WWI the british Osram was occupied and they start to produce early tubes.

Best regards, Hans-Thomas
John Turrill

Dear Hans-Thomas,
                              thanks again; I think I've seen the Babani
book you mean, pretty sure an old friend of mine had one, was
hoping I might persuade him to part with it, but never did!
The ones I have are a  "A Comprehensive Radio Valve Guide",
books 1 to 5. (reprints).
Now you've completed my education regarding Osram, I was
never sure of that situation, thanks for the information.

Best regards, John.

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