Spy tape recorder - EDI model M-75B

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     EDI model M-75B.    This recorder was produced by ELECTRO DATA INC in 1966 - 1967, and was freely sold to all comers. However, in fact, its history began much earlier, since it is an almost exact copy of the spy tape recorder UMY-25, which was developed by the order of the CIA, was produced approximately from 1962 to 1965, and was naturally a secret product. After 1965, when the CIA had a new technology, the recorder was declassified, and began to be produced as consumer goods.
     The device is really quite suitable for spy purposes, it is very small, lightweight, with a stabilized tape speed, and very durable, since the body is cast from an aluminum alloy. In addition, it is stereophonic, there is a function of auto-stop, rewind and fast forward, and the mechanism works very quietly. Dimensions of the recorder 130 x 72 x 25 mm, weight 225 g. The presence of all these functions in such a small apparatus of those times is surprising.
     In fact, the design is very simple, in the presence of pinch roller and capstan, there is no flywheel, and switching modes is done by turning the clamping bar to different angles. In the working position of the bar, recording or playback is performed. If you pull the bar to the end, you rewind, and in the intermediate position, fast-forward. To turn on the recorder, you need to connect microphones with a control switch, or headphones, to its connector. To trigger the hitchhiking a metal pin is isolated from the housing, which is located next to the supply coil. The pin is connected to the clip by a metal tape pasted at the end of the magnetic tape. At the same time, the transistor is locked, which in the working condition is the motor speed stabilizer, and it is switched off. The two-channel amplifier is assembled on the chips of WC183T, on a very small board, and it does not look serious, but it works. The quality is average, but apparently it can be considered serviceable, since both channels work the same way, and electrolytic capacitors have kept good parameters.
     At present, the device can be considered a conditionally working one. It records and reproduces, but the uneven movement of the tape is quite strong. This is due to the deterioration and deformation of the rubber of a large roller, and it will not be possible to fix it. You can not use the recorder for the intended purpose.

Video review

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The spy recorder UMY-25 had no logotype

A very small pinch roller is mounted on the clip. In this recorder, it is metal, and capstan is rubberized. It is clear that when storing the recorder pinch roller is always pressed to the capstan, in connection with which the rubber capstan strongly deformed. Repair of such a defect is a big problem, but I coped with this.

The electric motor was faulty, I had to disassemble it, and repair the rubber bushes into which the ball bearings are inserted.

In the photo below are visible white rubber bushes, and on the right the device of the centrifugal regulator

To power the amplifier we used a mercury battery RM-625 with a voltage of 1.4 v. Instead, I use a modern alkaline analog V625U - 1.5 v. To power the motor, a mercury battery RM-822 with a voltage of 1.4 v was used. I did not find a modern analog, and I had to assemble a 3-volt CR2032 lithium battery with a DC-DC converter for 1.5 v.

The year of manufacture is not indicated on the nameplate, but by indirect evidence I assume that this recorder was made in 1967. Apparently, everything looks very simple inside

Very interesting electrolytic capacitors. They are white, very small, and still retain good parameters, perhaps they are tantalum. Small size 3.5 x 1.5 mm with a capacity of 3 μf. Those that are larger, with a size of 6 x 3.5 mm with a capacity of 35-40 μF.

In the photo below, you can see how the tape is fed to use the auto stop function. The metal tape includes contact between the clamp and the pin isolated from the body

Unfortunately, I got the dictophone without accessories. I did not make copies of them, but to demonstrate the work I made a switch with connectors for connecting microphones and headphones. I use the Soviet microphone "Neva", which used to be used with Soviet special equipment.

The electric scheme of the dictaphone EDI.
I copied this scheme from a dictaphone, because on the Internet, nothing similar could be found