▲ Figure 1
This is the material of the Soviet pirated Japanese tape recorders of the last century.
01 Transistor Recorder
The two recorders below are close in appearance, right. The tape recorder trademark above is Tinico, which is a portable tape recorder produced in Japan in the 60s of the last century, personal entertainment. I don't know the logo of the tape recorder below, it should be Russian, Google translates as "Electron 52D", is a copy of Thetinico produced in 1967-1968 by Poltava in the Soviet Union (now in Ukraine), and now it seems that these two products are still quite exquisite.
▲ 图1.1 Tinico and Electron 32DTinico
The Tinico recorder measures 160×64×40mm and weighs 350g. Two batteries are used for operation, with two 1.5V AA batteries connected in parallel to power the motor, and the board is powered by PP3's 9V battery. Plastic enclosure. The motor that drives the tape does not have a constant speed measure, so the speed and tone of the sound will change as the battery is used.
The tape rotary drive motor in the recorder is located in the middle of the two tape reels, and the motor output shaft drives both reels at the same time before and after. The pulley is driven directly, and the pulley is driven by rubber friction.
The tape reel is 45 cm in diameter, and guess how long the recording will be played? 10 minutes (600 seconds).
▲ Figure 1.2 Audio Recorder operation button and microphone and headphone jack
The amplifier circuit uses two 2SB75 transistors (PNP type). There is a 3.5mm headphone jack on the outside that can be connected to headphones or microphones. There is no volume control knob on the outside.
A special eraser head was used to replace the original permanent magnet. The design was very simple as soon as possible, but the appearance and working sound quality of the tape recorder were still very impressive at the time, and it could be used for language recording. It is said that the Electro 707 tape recorder later replaced Tinico.
Below is the inside of Tinico, where it is possible to see that two 1.5V batteries and one 9V battery can be placed in the battery box. An audio amplification circuit consisting of two PNP transistors on the board, with an audio transformer on top for output headphone impedance matching.
Figure Tinico internal structure Electron 52D
The Soviet-copied Electron 52D was not strictly copied tinico, but there were slight differences and even some improvements. For example, the motor driving the hinge is 1.5V when recording and playing, and 3V when rewinding, that is, two AAA batteries are connected in series. This change is very clever, which saves the tape recorder rewind time. Tinico uses 1.5V in both playback and rewinding.
The board uses three transistors (GT109A×2, GT108A×1), eliminating the need for an audio transformer. With a slight change in size (160×67×44mm), the housing appears angular. The weight is still 370g. According to the feeling of the collectors (Russians), Soviet products are not worse than Japanese products, and they are better to work.
Figure Electron 52D internal circuit diagram
More complex analog recorders, models including Monacor, Elektra 770, Start-lite Pocket Mat, etc., are structurally similar to the recorders introduced above, with the addition of built-in speakers, motor speed control, and volume control.
Although there were many other tape recorders on the market in the same period, they were mostly very simple and more like a toy than the previous two.
The headphones equipped with the Japanese Tinico tape recorder at that time were piezo ceramic (so you can understand why the audio amplifier in the Tinico recorder needed to have a transformer output), but the Soviet Electron 52D used dynamic headphones with better sound quality and did not need to use an audio transformer.
▲ Figure Electron 52D appearance and its headphone accessories detail comparison
The photo below clearly compares the internal details of the products of Little Japan and Old Maozi. At the level of production process, the two are similar.
▲ Figure 1.2.3 Above is the tinico internal circuit board and structure; below is the internal structure of electron 52D
▲ Figure 1.3.2 Electron 52D tape guide and head part of the close-up
▲ Figure 1.3.3 Instructions for use on the transparent lid of the recorder
▲ Figure 1.3.4 Paper tape recorder operating instructions
02 Earlier tape recorders
You can see that the above portable tape recorders were only mass-produced in the 60s of the last century, and the recorders before that were large and clumsy desktop recorders.
As can be seen from the TV series lurking, even the military tape recorder provided by the Americans at that time had to be put in a suitcase. The agent who secretly recorded the sound of "Cuiping" needed to carry this large box in his hand to complete the recording.
Figure 2.1 A tape recorder used to eavesdrop on recordings in the lurking
The author of the web article Tinico and Electron 52D[1] and an electronic antiques collector has listened on several occasions to discuss why it was not possible to produce a portable tape recorder like Tinico around 1945 (when the transistor was invented in Bayer Laboratories). The main reason for this was that there were technical problems in the production of three main devices at that time:
1. Miniaturized motor;
2. Small electronic amplification circuit that can be loaded into the box;
3. Miniaturized batteries capable of driving tube anodes and filaments;
So the tape recorder that could fit in your pocket at that time was like you were already using an iPhone when everyone was still using Big Brother.
As for the back of the TV series, the underground party re-recorded the language of the agent through a small cassette tape recorder to edit the language, which can only be the director's romantic imagination.
Fig. 2.2 A cassette recorder used to steal and record enemy confessions
But for true electronic enthusiasts, it is doubtful whether a portable tape recorder could not be made before 1945. The authors of the web article Tinico and Electron 52D have made full use of pre-1945 electronic devices to create a tape recorder with the same appearance and functions as Tinico.
He found out through the patent that before 1945, there were already companies producing tube-based hearing aids, so tube-based portable audio amplifiers existed.
Fig. 2.3 A replica of a Tinico tape recorder made using a tube
After modification, all components can fit into Thetinico's same size enclosure. The performance of this modified portable voice recorder is the same as that of the transistor.
▲ Figure 2.4 Tinico of a pure electron tube
On the battery, the original +9V battery needs to be changed to a +30V mercury dry battery, which can drive the tube anode to produce enough power output.
▲ Figure 2.5 +30V battery for driving electron tubes
If the female agent at that time used this portable tape recorder, it is estimated that Comrade Yu Zecheng would be very dangerous.