A small module revived the huge «Leningrad-006-stereo» 26 декабря, 2021

expire

So the child of the Soviet radio industry of the highest class began to sing in a full voice. Let me remind you that the radio was made in 1979, but even 42 years later it sounds just as great.

As soon as I got this radio, I began to collect information on its restoration, so as not to step on the rake of my predecessors in this field a second time.

The LW range is definitely not needed anymore, but on the SV I would also like to drive the morning broadcast — at this time, due to the activity of the ionosphere, very distant radio stations are heard. But in the city there is no point in doing this, interference, and leaving for the dacha only next spring. The HF band is now quite boring: the Western «Voices» no longer see us as an ideological force and have closed their propaganda radio stations. All that remains is to listen to VHF broadcasting, which is no longer in the Soviet range (66-73 MHz).

To do this, first of all, you need to redo the VHF module. The scheme is already on the Internet:

With due care and attention, after such a revision, the VHF module will work in the modern range of 88-108 MHz. Here’s further from the series «how lucky.» There are many complaints that automatic frequency control (AFC) often loses the signal, and there are also frequent complaints about uneven sensitivity over the range: some radio stations catch perfectly, and some with noises, even the antenna does not help. It is also recommended to check the IF filter settings with devices. Well, the stereo decoder module can simply be thrown away — there is no sense in it.

Unfortunately, now there is no time to do all this with high quality, but I don’t want to do it «and it will do it that way.» Therefore, I immediately remembered about an interesting VHF radio receiver board from the Middle Kingdom, a kind

I was impressed by the excellent sensitivity and pleasant sound. So I decided to put it in «Leningrad» and from this module send a signal directly to the input of the amplifier.

To power this VHF module, you need a voltage of 3.7 V to 6 V. We have 12 volts in the radio receiver, so I immediately put a 5 Volt stabilizer on the module (KRENKA).

He also did not stand on ceremony with the location: on the radio receiver, the racks of the buttons of the UPCH-AM-CHM unit crumbled. I don’t need this module and I just removed the panel of these buttons, and the P2K switches themselves do not interfere.

Made a new panel from black plastic already for the Chinese VHF module.

I had to fight with the pairing of the VHF module with the amplifier of «Leningrad». The module sounded very nice on the headphones, but when the signal was fed to the amplifier, the sound changed. Having done some magic, I found out that the module definitely needs a load for high-quality sound. It was not possible to deceive by replacing the headphones with a resistor of similar resistance. There are good old headphones — I cut off a half from there and soldered to the board — the sound quality returned.

Replaced all electrolytic capacitors on the power supply and on the low frequency amplifier. Everything was weird, until I accidentally noticed that one of the new capacitors had blown up strangely. According to the diagram, this is a power supply filter on the ULF board. There was a 500 uF capacitor for 16 volts, and I put 2000 uF for 16 volts.

I had to urgently replace it, only 1000x50V was available. I already, by a sinful deed, begin to suspect that the Armenian manufacturers of capacitors have moved to China …

At the input of the amplifier, there is a rather complex circuit of loudness and filters.

To be honest, I have not completely defeated this scheme: at the lowest volume, incomprehensible distortions begin with the loss of the low-frequency component. It is worth adding a little volume, everything is normalized.

I could not resist the temptation and made a green illumination of the DV-SV scale. I was looking for a tape with yellow LEDs — not available, but with green LEDs I have been lying for a long time. So I kneaded two stripes — it turned out to be a very uniform and pleasant illumination of the scale. It will be necessary to make a separate box for the second scale.

Friends generally advised to make the backlight from an addressable LED strip — here and whatever color of the backlight you want, you can easily make it work in the spectrum analyzer mode (2 scales are 7 separate windows). It is even possible to transfer such a tape to the color music mode.

The most pleasant surprise was when I closed the back cover of the receiver — the sound became noticeably juicier. All the same, an excellent radio receiver was made by the guys from the All-Union Scientific Research Institute of Radio Reception and Acoustics (VNIRPA).

This entry was posted on Воскресенье, 26 декабря, 2021 at 1:31 пп and is filed under Uncategorized. You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.