Soviet industry produced the Riga-102 radio, its standard scheme for that time. To this day, you can find these devices in old houses, they often perform the function of furniture, working copies are very difficult to find.
But sometimes there are radio stations where you can listen to old records, tune the radio to the wave of your favorite station. Now this is a rarity that not everyone can restore, since there are very few elemental bases on sale, and if there is, then the price is sky-high.
Basic information
Radiola "Riga-102" was produced at a factory located in Riga, hence the name. This device allows you to listen to radio broadcasts in the following wave ranges:
- Long.
- Secondary.
- Short - this range was divided into two parts.
- Ultrashort.
Sensitivity in the ranges of HF, LW, SW - 20-60 mkv. For VHF, this parameter is 3-6 μV. Also, a drive for phonograph records was installed in it, the pickup was connected to a low-frequency amplifier.
Range switching was performed by buttons on the front panel of the radio. They are far from sensory, in order to press a button, one had to spend a lot of power. Not every child and even a teenager could switch ranges. In Soviet technology, this is not a new phenomenon, television channel switches also worked very tightly, and had to put in a lot of effort.
Acoustic system
The lower half of the Riga-102 radio, like many others, is almost empty. Only speakers and an antenna for operation in the ultrashort wavelength range were installed in it. On radios, three or four speakers were used. Two were located on the front side, usually with round diffusers. A pair of oval speakers mounted on the side walls.
The circuit of Riga-102 is very simple: the speaker system was connected using a two-wire cable with a small plug to a low-frequency amplifier. The power of the low-frequency amplifier did not exceed 10 watts. Today this is a meager value, the simplest amplifiers on a single chip can give more power. And the dimensions of such structures will be much smaller than the radiola.
Back wall
On the entire rear was a protective cover made of chipboard with slots. The main important data was applied to it: the purpose of certain conclusions on the instrument chassis. Here is a brief safety precaution. The labels warn the user that there is a high voltage inside. The tube cascades are powered by direct current, voltage 150..250 V.
The slots in the protective cover are made to remove heat, as the lamps become very hot. Therefore, it is not recommended to install the radiol near heating radiators. The back cover is fixed with two round latches at the bottom.
Turntable
Since these devices were produced in the 60s and 70s of the twentieth century (specifically, “Riga-102 Stereo” began to be produced in 1971), when vinyl records were at the peak of popularity, there was simply no way to do without a special player. The player was located under a massive wooden cover at the top of the radio. He allowed to reproduce the plates in the three-speed mode. Electric playing devices with the index II-EPU-40 and II-EPU-50 were mounted on the radiol.
They had 2 or 3 speeds of rotation, they switched using a mechanical device. A rubber roller connects the rotor of the electric motor and the inside of the metal disk on which the plates are mounted. A soft metal sleeve is mounted on the rotor of the electric motor. It is made in the form of steps with different diameters, which allows you to change the speed of rotation of the metal disc and record.
Pickup and plate rotation speed
The pickup rotates freely around its axis by a small angle, which is quite enough to reproduce the plate from beginning to end. When the end of the recording is reached, the motor is turned off and the pickup is raised. The pickup needle connects to the pins inside the case.
A shielded wire was drawn from these contacts to the low-frequency amplifier of the Rigada radio. The electric motor is powered from a 110 V alternating current network. If you look at the connection diagram, you can see that the power cable is connected to the primary winding of the transformer, and more precisely, to the extreme and middle terminals.
Low Frequency Amplifier (LF)
The bass amplifier on the radio is made according to the classical scheme, like most Soviet radios of that time. As a pre-amplifier, a double triode of the 6N2P type is used.
In the "Rigonda-102" circuit, one or two 6P14P lamps, which are powerful pentodes, are installed in the terminal cascade. When using two 6P14P lamps, it turns out to achieve an increase in power, as well as to implement a stereo amplifier circuit. There are few adjustments in the amplifier:
- Correction of sound at high frequencies.
- Low frequency adjustment.
- Change the sound volume.
All these controls are located on the front panel. On the back wall there is a connector with six holes for connecting an external microphone or sound source. For example, you can connect the output of a TV or tape recorder to a radio. There is also a jack for connecting the speaker system of a tube radio receiver.
KSDV-IF block
Such a terrible name, but it can be decrypted very simply. This is the unit that is responsible for the operation of the radio in the range of short, medium, long waves, as well as an intermediate frequency amplifier module. All this is necessary for the proper operation of any radio. This is the main board, which is located on the chassis of the Rigonda radio. It contains all the switches, as well as connectors for connecting to an external antenna and ground.
A piece of copper wire must be used as an antenna, preferably a few meters in length. Telescopic antennas cannot be used for good reception in the short, medium or long wavelength ranges. The output of this unit is connected to a low-frequency amplifier. An indicator is also connected here, which is located on the left side of the front panel - this is a green lamp.
On the right side of the circuit board is a variable three-section capacitor, which is connected to the scale on the front panel. To move the arrow, a complex mechanism is used, consisting of plastic blocks, threads, springs. It is precisely such pointer designs (as in the Riga-102 circuit) that were used in most Soviet radios.
VHF unit
This unit, which is located in the far right corner, it has a separate variable capacitor of a special design for tuning. Therefore, if you want to listen to two different radio stations that broadcast in the ranges of short and ultrashort waves, you only need to make a one-time tuning, after which you can only switch the buttons on the front panel.
The block is made on only one lamp of the 6N23P type. It provides reliable reception of the main broadcasting radio stations in the range of 65.8-73 MHz. It is in this interval that the youth station known for all is located. Today, its broadcast is easier to listen to on the Internet than on a radio.
Pirate Radio
In the Soviet years, radio circles were common in which children and youths were taught how to assemble circuits, make receivers, and various electronic toys on their own. But this did not end there, so many young people went further, making special radio transmitting devices. But broadcasting in civilian bands was illegal, direction finders drove through the streets in cities and towns to identify violators.
UHF "Rigonda-102" was used as part of a radio transmitting device - a microphone or tape recorder was connected to its input. Modulation voltage was removed from the anode of the output lamp, which was supplied to the simplest master oscillator. It was made on the most popular lamp - 6P3S. Details of the master oscillator:
- Variable Capacitor.
- Inductor.
- Lamp 6P3S. Could be used 6P14P, 6P15P, 6N8S and the like.
- Constant capacitor.
These are all elements, with their help it was possible to go on the air and broadcast to a small city or village. The scheme "Riga-102" made it possible to implement a simple transmitter. Youth “twisted” their favorite music. As a rule, it was a domestic stage, as well as "forbidden" groups such as the Rolling Stones, The Beatles, Boney M and many others. Some hams moved into the "big" league - assembled more powerful devices and competed with their colleagues in the communication range.
Alteration radiol
Most of the USSR radiolas were performed exclusively on lamps. Toward the end of the 80s transistor players with integrated receivers began to go on sale. They were smaller in size, practically safe, since the circuits were powered by a direct current of no more than 24 V. But they are also imperfect, there are a lot of shortcomings in them. The modern elemental base allows you to completely remake any radio, to change it beyond recognition.
Only the wooden case, speaker system, chassis, electric player should remain from the old radio. At the Riga Radio Plant, many modifications of radiol were made, which are currently outdated. They can either be restored or modernized. There is a sense to restore only if you plan to bring it to a state close to perfect, so that you can later sell it (or keep it to yourself if you are collecting radio equipment).
But you can do a complete alteration of the "Riga-102" by installing a modern stereo amplifier on the chip. It can be made either independently or purchased ready-made. Chinese ULFs with tone control, the ability to connect a subwoofer are quite cheap - the simplest ones have a price of 500 rubles or more. If there is a need for a radio receiver, then you can install a unit that allows you to listen to stations in the VHF band.
The main thing is to turn the tube radio into a multifunctional device that can "read" any type of media: phonograph records, CDs, flash drives and others. But if you do not want to modernize your rare equipment in this way, it is better to do restoration, to achieve a state close to the one in which the radiola was at the time of sale. This is difficult to do, but with a little persistence, you can achieve the goal.