Good afternoon! I have a Whirlpool WMS20SW microwave that does not turn on the display when connected, but when the door is opened the light and the turntable turn on. I have read in other posts that the problem could be due to microswitchs or failing that to the relays of the board that are activated with the closing of the door. But I have already verified that the switches and relays are in perfect condition. I have removed the board and started testing. I have verified that the power supply is working correctly. The source of this microwave is a transverse plate on the main plate and delivers 5V for uC and 12V for relays. The voltages are correct and the 5V are present in the uC, just like the 12V are present in the lines corresponding to the relays. Continuing with the tests and almost by chance I discovered that in the sector of the circuit that relates to the relay that is activated with the closing of the door; by short-circuiting the collector with the base of a transistor, the plate turns on, then I can remove the bridge and the board remains on and works normally. I can schedule the time and start. When starting the relay indicated as "VPC" closes the circuit so it would theoretically begin to heat. Here I leave the circuit around the transistor referred to above. The diagram corresponds to the entire line related to the relay that turns on with the door closure, and to the transistor that, when short-circuiting, turns on the board: * The bridge I refer to is indicated by the red arrows. I add that I have reviewed all the components involved in the diagram I drew. Transistors Q2 and Q3 are indicated as H03, which according to the data sheet are DTC343TK transistors that are SMD transistors with an integrated resistance in the base. Loes replace with a bc548 with a 4k7 base resistor as indicated by the DTC343TK data sheet. I have also replaced Q1 taking into account that it is PNP, I have changed the capacitors, I have removed and checked the 1N4148 diode and I have failed the resistors. Everything is correct. I add that although it seems weird that in my diagram the Q2 collector is offline, this is how it is on the board. since that collector goes to the transistor that turns on the relay that connects the GRILL, but since this microwave model does not have a grill, that transistor does not exist, and there are no traces that there has been anything solased in that place. and the track does not continue to any other part. That is why the collector of Q2 is offline. In addition, the bridge between the base and the emitter of Q2 turns on the plate whenever the door switch is open, if the switch is closed (and the emitter of Q2 to ground) the plate does not turn on. Once lit, even if you remove the bridge, it is already lit and operable. that is to say, in practice, if I connect the microwave, and make the bridge, when I open the door the plate would turn on and the microwave will already remain operable. as long as you do not open the door the microwave will not turn on. So do you have any idea how to solve the problem? Did something similar ever happen to you? since leaving the base bridged with the Q2 transmitter does not seem the most elegant. REGARDS!!