K174un14 what is your opinion about her. Audio amplifier on a Soviet microcircuit

Old TVs are gradually losing ground, ending up in dismantling, or worse - in the trash. Well, one day I came across one, well I always carry a folding screwdriver with me... One of the perfectly working boards was a ULF board. And the TV is “Selena” (“Horizon 51-TC418”).

The board, among other parts, lay there for some time until it was necessary to make a simple intercom for a country house. The diagram is shown in the figure. It was born under the influence of some articles from the Radioconstructor magazine, which, unfortunately, I do not have the opportunity to list, for which I apologize.

Scheme for converting the ULF module

In the center of the diagram is a diagram of the ULF module above the indicated TV. The module is made on the K174UN14 chip, in addition to the ULF itself, there are also tone control resistors R2 and R4, as well as turn off S, which can be used to turn off the speaker in order to connect headphones. The ULF module circuit has undergone changes, which are shown in the diagram.

Since a tone control is not needed for an intercom, but a volume control is simply necessary, this tone control was converted into a volume control. The volume control was a variable resistor R4. To do this, it was necessary to remove R3, R5, SZ and C2 from the circuit.

Instead of SZ, put jumper P1, and together with C2 put a capacitor of larger capacity (0.33 μF). Now the former HF tone control R4 has turned into a volume control.

Rice. 1. Connection diagram for the ULF module of a TV as an intercom.

In addition, it later turned out that the sensitivity of the ULF is not enough to work well with electret microphones, so it was decided to increase the transmission coefficient of the K174UN14 microcircuit by changing its OOS by increasing the resistance of resistor R9. Instead of 330 Ohms, 680 Ohms are supplied, but this needs to be clarified specifically.

Now about the operation of the circuit as a whole. A passive unit is installed at the input, consisting of speaker B1, electret microphone M1 and bell button S3. The calling system works independently and is a standard apartment bell scheme, the only difference is that it is installed not near the door to the apartment, but on the fence, near the gate for entering the summer cottage.

S3 - a bell button, so as not to get wet, is protected by a tube cut from a plastic bottle. From it, a double wire for 220V goes into the house, and there is a regular apartment bell ZV1. In general, this call scheme existed even before the intercom appeared, but now you don’t have to run straight to the gate, but talk first.

The active node is installed in the house, and apart from the bell, it is connected to the passive one with only one shielded audio cable (for the stereo signal). The speaker terminal B1 and the negative terminal of the microphone M1, connected together, are soldered to the braid.

Switch S2 is used for transmit/receive control. It is without fixation, a button. In the non-pressed position, as shown in the diagram, you can listen to the interlocutor - the guest. And to answer, you need to press S2 and hold it down while answering.

S1 - power switch. As long as no one calls, you can turn everything off. Microphone M2 and speaker B2 are located in the house.

And so, a call came in, we turn on the circuit with switch S1. In this case, S2 is not pressed and is in the position shown in the diagram. Microphone M1 receives power through resistor R101 (designated with a three-digit number to differ from the numbering of resistors in the ULF module diagram).

By selecting the resistance of this resistor, you can set the sensitivity of the M1 microphone during the process of setting up the intercom. Through the cable, the upper section S2 in the diagram, the signal from microphone M1 is supplied to the ULF. Using variable resistor R4 you can adjust the sound volume. From the ULF output on the K174UN14 chip (switch S of the ULF module must be closed), the signal goes through the lower section S2 in the circuit to speaker B2, located in the house. Thus, what is said in front of M1 is heard from B2.

To answer, you need to press S2. At the same time, the M2 microphone located in the house is connected through its upper section according to the diagram. Power is supplied to it through resistor R102.

By selecting the resistance of this resistor, you can set the sensitivity of the M2 microphone during the process of setting up the intercom. The signal from microphone M2 through the upper section S2 in the circuit goes to the ULF. Using variable resistor R4 you can adjust the sound volume. From the ULF output on the K174UN14 chip (switch S of the ULF module must be closed), the signal goes through the lower section S2 in the diagram to speaker B1, located near the gate. Thus, from B1 you can hear what is said in front of M2, and the guest will hear you.

Parts and replacement

The ULF module in the TV is powered by a voltage of 15V. Here it is powered from an external 12V voltage source; the source diagram is not given, because this is a regular network adapter purchased in a store. The supply voltage can be from 8 to 16V.

Electret microphones are of an unknown brand, ordinary, with two terminals. They can be replaced with almost any type for electronic telephones, tape recorders, etc. Select resistors R101 and R102 in each specific case to obtain the required sensitivity of the microphones.

The B1 speakers are both elliptical speakers from the same TV. But almost any broadband will do. For a passive block with M1 and B1, you need to consider a waterproof design. It is advisable to place a speaker with a paper diffuser in a plastic bag. If there is no ULF module from Selena, you can assemble the ULF on the K174UN14 IC.

Goidin V. A. RK-2016-04.

Control amplifier from TV.
The ULF module was taken from the TV and placed in a housing. A power adapter is used for power supply.
Finally, times have come for us like in the West - people display used equipment, even in working order, near trash cans. This is from an old TV fourth generation type 4USTST (Specifically, the Horizon 418 TV is taken), you can tear out one interesting block called MU-405.

When looking at schematic diagram You can see that this is a ready-made ULF with a power of 5 Watts on the K174UN14 microcircuit (the microcircuit is an analogue). All that remains is to screw on the volume control and put it all in a suitable box.

Which was done immediately. Only the suitable box could not be found. Therefore, foil-coated PCB and fiberglass PCB were quickly sawed. I haven’t encountered textolite for a long time. I was unpleasantly surprised by its much worse processing ability than fiberglass.
Then, using a soldering iron, all the pieces were soldered into the case. The top cover was made removable. I sanded everything with fine sandpaper and painted it with spray paint. A variety of input and output jacks are provided for versatility. To reduce the size and weight, and also not want to connect 220 V to the power supply, I decided not to bother. The solution is simple: I, and everyone, have many different devices powered by network adapters. For example, charging from a cordless screwdriver or charging from a camera. After all, they are not used very often. You can download them during unused times. A small nuance. Typically, these power supplies are located in a solid casing and become noticeably hot during operation. Therefore, holes were drilled in the adapter housings for ventilation.

In order not to think about polarity, I installed a diode bridge. Of course, the input connector for power is isolated from the common ground. By the way, when connecting the power, I stepped on an earth rake. The amplifier in the box is phony. But it only generated noise from network adapters. When connecting a separate stabilized power supply there was no background. I couldn't find the reason for the background. Hanging capacitors did not help. The background disappeared when the power wire was soldered into place. And I soldered it where it was more convenient. The button to turn on the headphones is used as a –20 dB input divider. This divider is borrowed from the Vega U120 amplifier. It is interesting because there is continuous switching and there is no click in the speakers.

I removed the headphone jack. If desired, you can increase the power of the amplifier by replacing 2003 with 2030. There will not be very many alterations. Or even make a stereo version of two such control modules

In this article I will tell you how to assemble a simple and small-sized audio amplifier using the TDA2003 (ILA2003) microcircuit, its domestic analogue K174UN14 (I once hid it in a matchbox). The amplifier is intended for use in any design as a main or additional ultrasonic sounder; I used it as an amplifier for a phone, taking a speaker from a computer and placing the amplifier in it. This amplifier has the following parameters:

Operating frequency range…………………………………………………………………………………20-20000 Hz.;
Maximum output power, (Rn=4 Ohm, THD=10%) not less than………………….5 W;
Supply voltage range………………………………………………………………………………………6…18 V.

The amplifier circuit is very simple and very reliable. It has a wide range of supply voltages and is practically indestructible. It has overload protection (I checked it on a short circuit; after working for 3 minutes, the microcircuit got hot like an infection, but it didn’t fail, but it’s better not to experiment). When purchasing all the parts, this ULF will cost you somewhere around $2-3.

The amplifier is adjusted by selecting resistance R2 for minimal distortion at maximum volume. However, I would not recommend that you apply too large a signal to the input (with an amplitude of more than 1 Volt), in order to avoid input overload and further failure of the microcircuit. In principle, the RxCx circuit need not be installed if without it there is no self-excitation of the amplifier at high frequencies.

This is what the chip looks like:

I assembled my first amplifier by simply soldering all the elements together (I did a little searching on the computer and found a photo of it).

My first amplifier on TDA2003 😀

Just don’t write that you could have printed circuit board collect. At that time I didn’t have time to work on a printed circuit board, but it was much faster this way :)

It's of course up to you where you use it, but I'll tell you how I used it. Subsequently, the amplifier was placed in the speaker housing from the computer along with two batteries from mobile phone. The batteries lasted for about 2 hours, listening to music loudly and loudly. good quality, and then it got a little worse, then I turned it down a little and I could listen for another 1.5 hours. Here is a photo of what I got, as you can see, everything is glued together with tape, but the main thing is that it works (sorry for the quality of the photos)

Audio amplifier, assembled on the Soviet microcircuit K174UN14. According to factory data, the 174un14 microcircuit is a low-frequency amplifier with a nominal power of 4.5 Watts. Compared to k174un7, it has better and more sophisticated protection against overheating and overloads, protection against short circuits at the output, as well as against reversal of the polarity of the supply voltage. I found this microcircuit on a scarf in my bins, checked it - it turned out to be working, and in order to give the circuit a look and compactness I decided to remake it for myself. See the diagram below:

I found a signet on the Internet - adjusted it so that the dimensions were 30x35 mm, etched the scarf and assembled it (), initially I somehow didn’t like the sound - it locked and was quiet. It turns out that in the circuit from the reference book on Soviet microcircuits there is a 22 Ohm resistor - this is clearly too much! There should have been 2.2 ohms! I looked for a resistor and found it at 10 ohms - soldered it in, the sound situation improved significantly.

Then it was decided to take two 1 Ohm resistors, imported, and connect them in series and install them on the board. The sound turned out clear and loud, which is what was required!

The ULF speaker of 5gd and 3gd swings well. I installed the microcircuit on the original cooling radiator on which it was located, smearing thermal paste between the microcircuit and the radiator. I screwed the board and the radiator together with a self-tapping screw, for reliability, now nothing wobbles, and the radiator turns out to be mechanically connected to the radiator - no substrate is required, since the minus of this microcircuit is designed for connection to the case.

I power the ULF circuit from a pulse generator, while a capacitor on the board of 1000 microfarads is enough, the voltage is 12.5 volts. In the pictures that I attach to the article, you can see the typical connection and typical factory parameters for the microcircuit.

The input is supplied through a 22 uF electrolytic capacitor; in the future I plan to hang the input with a 10-20 kohm resistor to the ground so that it does not emit unnecessary background when the plug is, so to speak, in the air without a connected signal device. The temperature of the microcircuit is within normal limits, and approximately 45-50 degrees after 30 minutes of operation at 80% power. redmoon was with you.