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AEG Telefunken M-36
Military reel-to-reel recorder

M-36 was a military portable reel-to-reel 2-track audio tape recorder (German: Tonschreiber), developed by AEG Telefunken in 1971 for the German Bundeswehr (Army). The recorder was typically used for presentations (often in combination with a slide projector) and for recording radio conversations, for example as part of an intercept suite. It was suitable for use in fixed stations as well as in mobile envoronments, in which case it was supported by a vehicle mount.
 
The device is housed in a die-cast lightweight enclosure with a hinged top lid. All controls are at the front, whilst the connections are all at the rear. It measures just 33.5 × 25.5 × 11 cm and weights approx. 7 kg. Standard tape reels are used, which and can played at 4.75, 9.5 or 19 cm/s. When small diameter reels are used, it is possible to run them with the top cover closed.

The image on the right shows a typical AEG Telefunken M36 with a tape in place and the top cover removed. The latter is only possible after removing the two C-clips from the hinges.
  
M36 with tape loaded

The M-36 is suitable for recording and play-back, for which all connections are available at the rear. As it is a professional device, balanced inputs and outputs are available, as well as single-ended outputs on banana-type sockets. Audio is delivered on a small speaker that is integrated with the front panel, or to a pair of headphones, selectable with a toggle switch at the front.
 
M36 with top cover closed Front panel Connections at the rear Opening the top lid M36 with top lid open M36 reel-to-reel tape recorder M36 with top cover removed M36 with tape loaded

 
Controls
The diagram below shows the front panel of the M36. At the left are the settings and indicators for the recording level of both input channels (I and II). At the centre is a round speaker with volume controls. At the right (somewhat bulged out) is a rotary knob for selecting the required MODE of operation (record, play-back, winding). Pull-out the knob to select the (red) recording modes. The tape is started and stopped with the two push-buttons above the MODE-selector. A small red indicator, in between these buttons, will be lit when the end of the tape is reached.


All connections are at the rear. As the device was intended for military applications, standard military-grade sockets are used. All inputs and outputs at the top row are balanced. Unbalanced outputs are available on banana sockets. Headphones should be connected to the banana sockets at the lower right. A 24V DV power source should be connected to the 3-pin socket at the far left.


The image above shows a top view of the M-36 on which a small supply tape-reel is currently installed. In this case, the pick-up reel is somewhat larger. The tape is guided from the supply reel, past the leftmost tension arm, the magnetic heads, the capstan and the rightmost tension arm, onto the pick-up reel. Three standard tape speeds are supported, and can be selected with the 3-position rotary switch at the right. When the MODE-selector (at the front panel) is set to winding (↔), the winding speed can be adjusted proportionally with the knob at the front left.
 
Interior
Getting access to the interior of the M-36 is very simple. If the mechanics section has to be serviced, the top panel should be removed by taking out 7 hex screws and lifting the panel upwards. This gives access to a die-cast magnesium frame that holds the motors, pulleys, etc.
 
When the underside of the mechanics frame has to be serviced, or when the electronic circuits have to be accessed, it is not necessary to remove the top panel. Just loosen the red hex bolt at centre of the right edge of the top panel and use the knob to pull the hinged frame upwards. It can be locked in vertical position.   
Perspective view of the M36 with top panel removed

 
Perspective view of the M36 with top panel removed Top view (with top panel removed) Recording heads and main assembly detail Raising the mechanic frame Locking the frame in place Open M36 with mechanic frame in vertical position Electronic circuits in the bottom section Electronics details

 
Connections
DC input
  1. Ground (chassis)
  2. +24V
  3. 0V
Audio inputs
  1. Ground (chassis)
  2. + input
  3. - input
Audio outputs
  1. Ground (chassis)
  2. + output
  3. - output
Remote control
The M36 can be remote controled (start/stop only) from a handheld remote control unit, or by another M36 unit. The latter is useful when using the master/slave function to start a second recorder when the first one reaches the end of the tape. The diagram below shows the pinout of the 10-pin female socket marked Fernsteuerung (remote control) at the rear of the machine.
 
  1. Stop (in) 1
  2. Remote start (in) 2
  3. Start (in) 1
  4. Lamp 3
  5. Lamp 3
  6. not connected
  7. Tape-end (out) 2
  8. +18V DC (out)
  9. Electrical ground
  10. Chassis
  
  1. Activated by applying +18V from pin H.
  2. Pins B and G should be cross-connected between two machines (for master/slave operation).
  3. Lamp 28V/40mA for tape-end warning (output) between pins D and E.

Technical specifications
  • Power
    24V DC (internally stabilized at 18V)
  • Speed
    4.75 - 9.5 - 19 cm/s
  • Size
    337 × 324 × 110 mm
  • Weight
    7 kg
Documentation
  1. Telefunken M-36 service manual
    February 1971. Obtained from [1]

References
  1. Elektro Tanya, Telefunken M36 Service Manual
    Website. Retrieved July 2016.

Further information

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Crypto Museum. Created: Saturday 16 July 2016. Last changed: Friday, 02 December 2016 - 08:27 CET.
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