COMAX CIOT-D20M IP camera repair, very low current on MC out pin [solved]

[Nifty]

Hi Everyone!

I'm trying to repair an IoT door video camera (COMAX CIOT-D20M), the video from the camera is transmitted, but some time ago the door lock opening function stopped working. The camera has a connector for connecting to a relay output, NC-NO-COM.

Relay is 5V DC, current consumption about 40mA, contacts are OK.
The relay is controlled by a microcontroller, a fairly standard scheme.
At the output, a current-limiting resistor, then an NPN transistor, a diode in parallel with the relay. The diagram is shown below.

After the command to open the doors is received, the corresponding output of the microcontroller switches to a high state. If I remove the resistor R1 (no load) - the voltage at the output of the microcontroller is 3.3V.
But under load (Q1), the voltage at the base of the transistor drops to 0.7V. This means that the microcontroller is not able to provide even a current of 0.35mA. And the transistor because of this does not provide sufficient current to the relay coil.

As I understand it, the output of the microcontroller is somehow damaged. Maybe someone can suggest a trick to deal with this problem.

P.S. Without Q1, voltage drops to ~2.5V (on R3).

[Nifty]

After some experiments, transistor Q1 (MMBT3904, NPN) was replaced with 2N7002KW (N-FET). Since the N-FET is voltage controlled, the problem is solved - the relay control works again.