Where is the mistake in the diagram?

Question

Electronics

Tell me what the problem could be, I soldered the circuit according to the figure below

, only instead of MP39 transistors I used MP25 (they are of the same structure) it should work. So, without a load at the output, when I measure with a tester, everything works, when I connect the relay, the voltage drops to 0.8V. Help solve the problem

Answer 1

Is the power supply enough to operate the relay? Connect the relay directly to the source and check the voltage.

Answer 2

Sounds like the relay is wired wrong. What kind of relay is it in general, by the way, in parallel with the relay, it would be nice to put the diode in the reverse connection, otherwise you can break through the transistor.

Answer 3

Look for an error in the installation.
Close the collector and emitter of the second transistor, if the relay does not work, then most likely the third transistor is not working. It can be tested by shorting its base and collector. If at the same time the relay does not work, then finally check the correct connection of the relay by closing to and e of the third transistor. In general, if the voltage drops like this, then most likely somewhere a short circuit.