Problem — lost signal from the antenna
The situation is different, the TV stopped showing, writes: “ No signal” . There can be many reasons, but today we will focus on the power supply of the antenna amplifier.
How to check it if you do not have a device at hand. Or you don’t have a device at all. And you don’t even know how to use it. This method is just for you.
Of course, this method cannot be used to completely check the power supply. But for a general assessment, whether it works or not, this is enough. And also using this method, you can check the correct connection of the antenna, cable and amplifier.
And to check, we don’t even need to disassemble or screw anything. And we will only need a nail or a screwdriver will replace it
To understand the principle of verification a little theory
First, let’s look at standard power supply circuits for antenna amplifiers. And let’s start over with a simple power supply without adjustment.
This is how the power supply circuit looks like as well as its appearance.
We unscrew the two screws and disassemble the power supply. Inside we will see a transformer and a small board such as in the photo or similar to it. (As I said, we don’t have to disassemble anything to check.)
I am one of the main details in the diagram is the 78L12 stabilizer microcircuit. This is a small black plastic piece with three legs.
But that’s not the point. The main thing is that short circuit protection is built into this microcircuit.
And therefore, if on the plug where we screwed the cable we plug the contacts of the braid and the central core with a nail or screwdriver, then a short circuit is obtained. We just need this. The protection in the microcircuit will work and the LED will go out. We remove the nail, the circuit disappears and the LED lights up again.
And this already tells us that the wire from the power supply to the plug is normal. And the power to the plug and cable is suitable.
Now we carry out the same manipulations with the circuit on the antenna itself. Or rather, on the amplifier where the second end of the cable is connected.
If the LED during the circuit goes out and then lights up again, then the cable is connected correctly and the power to the amplifier is suitable.
This tells us that our power supply is working and all connections are connected correctly. And if we lost the signal, then the reason must be sought in something else, and as a rule, this is an amplifier.
Below is a diagram of an adjustable power supply and its appearance. Since the principle of their operation is very similar, we will not analyze its work in detail.
The voltage at the output of the power supply unit is low 12 volts. But still try to follow the basic safety precautions.