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A simple DIY signal generator


Hello, friends the inhabitants of our site! Many of you have been able to repair failed radios and low frequency amplifiers.

The next home-made, which I did, is just useful for these purposes. This is a simple signal generator that can be used to check not only the sound path of the receiver, but also the radio frequency. His diagram is shown in the photo.

This is an ordinary multivibrator that generates oscillations not only of one fundamental frequency, but also many more multiple frequencies, called harmonics, up to the frequencies of the short-wave range.

The generator consists of two transistors. The output voltage taken from the resistor R4 through the isolation capacitor C3 is fed to the input of the amplifier or receiver we are testing. If an undistorted tone sound corresponding to the oscillation frequency of the generator is heard at the output of the receiver or amplifier in its loudspeaker, then the devices we are testing are faulty. And if the sound is distorted or completely absent, then this indicates a malfunction in their circuits. To create a homemade product, we need the following parts and tools.

it: two transistors KT 315A, MLT resistors - 0.25 W 3 kom - 2 pcs, 47 kom - 2 pcs, capacitors 0.01 μk -2 -, 0.05 μF - 1 pc, any small button, 1.5 V battery, one clip "crocodile".

Instruments: soldering iron, tweezers, solder, mounting wires, wire cutters, pliers, small case, needle, M2 screws and nuts, brass plates for the battery holder, mounting circuit board measuring 1.5 cm * 7 cm.

We assemble as follows:

Step 1. We check all the radio components for their performance with a multimeter. We solder the whole circuit on the printed circuit board. Check the correct assembly.


Step -2. In the case we have, we fix the button and the battery holders.


We put the battery in the case, connect the soldered board. We connect the head phone to the “A - B” output, and check the operation of the generator on the table. If the circuit is assembled correctly, then it starts to generate sound signals that are heard in the headphone.

Step -3. We fix the board into the case, solder the output “A” to the needle, and the output “B” - we bring out the black wire with the crocodile clip soldered at its end.

Close the case with a lid.

The main frequency of the signal is about 1 kHz, the output signal is about 0.5 V, the current consumption is not more than 0.5 mA. The batteries last for a whole year.

That's all, the homemade product is ready. And whether you need it - decide for yourself.

Good luck to you all in your affairs. See you again.
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11 comments
Guest Vladimir
With this generator, check only multicore cables, it is dangerous for radio devices.
And this probe is not intended for full verification, only to evaluate whether the circuit is “breathing” or not and to search for a “dead” cascade. And in many cases he will cope with this.
This generator has a small but significant drawback. With such a high amplitude of the output signal (0.5 Volts), if it does not burn the device under investigation, it will cause such an overload and signal penetration that it will be difficult to understand which of the cascades works (amplifies) and which simply passes the signal. Even a non-working cascade, at such an input level, can pass through itself.
And just add the simplest attenuator. Fixed and variable resistor. Judging by the photo, there is free space in the case. The axis of the variable resistor is brought out.
You can even put on a pen and draw a scale, albeit with an error. Then it will be quite ... boss
It is possible to continue further: the capacitors do not say “micron” after the nominal value, the button should be marked “S”, and the transistors “V” or “VT”.
But compared to some of the schemes presented here, this is a masterpiece. ;)
On the battery, a long line is indicated by +, the arrow on the emitter T2 is not indicated and there is no point on the connection R3, C2 and T1.
This is all the little things compared to the world revolution :)
vit
There are three errors in the scheme.
This is an ordinary multivibrator that generates oscillations not only of one fundamental frequency, but also many more multiple frequencies, called harmonics, up to the frequencies of the short-wave range.

After that, I don’t even want to read further.
This multivibrator generates oscillations of ONE frequency only, which is determined by the parameters of RC chains. But the signal has the form of rectangular pulses. A rectangular impulse can be represented using the Fourier series. If in a simple way, then this is the sum of a bunch of sinusoidal harmonics. That is why such a multivibrator creates interference over the entire radio range.
Check with such a generator UHF - mockery. Where is the guarantee that the ultrasonic ultrasonic excitation is not excited at frequencies from the ultrasonic range? In this case, the SOI will be very large.
The best use for such a generator is flashing lights on a Christmas tree.
Viktor960
And you offer something better from this millennium
I can offer you to type in a search engine something like: “soft signal generators”, “programs for oscillators and oscilloscopes”, you will be pleasantly surprised!
Easy, on the LA7 a pulsating generator. And you, boy, are behaving insolently. I can blind, shoot everything, only who needs it.
Author
And you offer something better, from this millennium. And we will look and appreciate your homemade product. And you can only blame everything that is posted on the site bgm.imdmyself.com. Go ahead, dare!
About 75 ... 80 year past centuries millennia. lol

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