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41MP

Information - Help 
ID = 15284
       
Country:
Great Britain (UK)
Brand: Cossor, A.C.; London
Tube type:  Triode, vacuum   Power/Output 
Identical to 41MP = CV1458
Similar Tubes
Normally replaceable-slightly different:
  104V ; ML4

Base Europe 5-Pin (O5A, B5) (Codex=F)
Filament Vf 4 Volts / If 1 Ampere / Indirect / Parallel, (AC/DC)
Description

Constructed as tetrode with 2 grids. Grid # 2 is connected to the anode rod via a spiralised resistor wire.

 
Text in other languages (may differ)
Literature Taschenbuch zum Röhren-Codex 1948/49   
 
41mp_1.jpg
41MP: RFJ
Roy Johnson

 
7_56.png
41MP: Telefunken Werkstattbuch
Wolfgang Bauer

 

Usage in Models 1= 1931 ; 1= 1933?? ; 4= 1933 ; 1= 1934 ; 3= 1935 ; 1= 1936 ; 2= 1937 ; 1= 1938

Quantity of Models at Radiomuseum.org with this tube (valve, valves, valvola, valvole, válvula, lampe):14


Forum contributions about this tube
41MP
Threads: 1 | Posts: 7
Hits: 1707     Replies: 6
41MP, triode connected tetrode, please explain
Nicolaas van Dijk
10.Mar.16
  1

I have a 41MP triode, but looking at the interior, it is a tetriode. The second grid is internally connected to the anode via a small spiral. may be just to prevent mechanical stress or it may be a resistance. Can anybody tell me what the reason is for this construction?

Attachments

Wolfgang Holtmann
10.Mar.16
  2

You are right, the second grid is tied to the anode.

Here is the explanation by the manufacturer:


In fact, with this trick the anode get's closer to the control grid and the claimed Mutual Conductance
of 7.5 mA/V is achieved.

41MP

Kind regards.

 

Jacob Roschy
11.Mar.16
  3

I don't understand what's the advantage to mount a second grid close to the control grid and tie it to the anode, then mount the anode itself just as close to the control grid ?

Best Regards,

Jacob

Dietmar Rudolph
11.Mar.16
  4

The advantage of this construction may be threefold.

  1. No new design for trode or tetrode is necessary.
  2. Reduced capacity between grid and anode unlike a triode having its anode in the distance of the 2nd. grid.
  3. Heat dissipation can be increased while the first grid stays cooler.

Best regards,

Dietmar

Nicolaas van Dijk
12.Mar.16
  5

Dear Dietmar

I respomd to you, but really like to thank all of you for the answer. The reasons seem clear and indeed, the valve has a very high transconductance. Perhaps I like to try the 41MP one day in an amp to see how it behaves, interesting

regards

Wolfgang Holtmann
12.Mar.16
  6

Another advantage -due to the high Mutual Conductance- an additional lf-preamplifier may be obsolete.

On the other hand,
as already stated in the Manufacturers Info, no large output can be obtained.

The reason for this is given in the Technical Data below:

Because of the little distance of the second grid (at anode level) in respect to the control grid, the anode voltage is limited to 200 volts!

Kind regards

Jacob Roschy
13.Mar.16
  7

Since this design was not continued in newer types, it may not have fulfilled as was expected. As only 12 models used this tube, it could be considered as a non-starter.

The reduced capacity between grid and anode may not be of much importance for an audio output triode.

While the heat dissipation of the anode can be increased, the thin windings of grid # 2 are even more endangered for overheating, hence grid # 2 is connected to the anode via a spiralised resistor wire as current limiter.

Best Regards,

Jacob

 

 
41MP
End of forum contributions about this tube

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