At the moment the laptop doesn't even turn on. What I noticed is that the small light-emitting diode doesn't even indicate that the laptop is connected to the power supply. The power supply shows the voltage output.
The repairer said straight away that the graphics card is broken. I mean, however, the switching unit that does not work between the battery and the mains connection. The switchover can be heard by a clear click (relay switchover).
The repairer earns more with a graphics card change than with a relay change or the corresponding assembly. Could the repairman have considered this thought?
So as a non-expert to express your opinion on such topics is always a bit critical, which is why I can only agree with your assumption that it has something to do with the power supply.
As I understand it, the laptop should boot despite a defective graphics card, since a graphics unit is built into almost every CPU
As a tip I would give you to go to another repairman who will also look into the problem
