Greetings to all. They gave me a notebook Lenovo B590 code motherboard LB59A MB 12209-1 48.4XB01.011 whose circuit diagram is Wistron LA480.
The PC is not lit at power. I replaced the fuse F3801 and the mosfet PU3801 but downstream there was a short circuit that I found to be the PU4302 FDMS3606S, but not being able to find it in Italy
I bought one that seems to be completely equivalent FDMS3616S. Now the computer charge the battery regularly and once lit displays the startup logo, is about 5 seconds sometimes makes me enter the bios, but then goes off and then power on and off almost loop. This problem does either only power supply, either with only one battery and is with both sources. After several tests and measurements I noticed that at the time when it is turned on
pin 1 of PU4302 and PU4304 I 1.7V while on pin 1 of PU4402 initially have a pulse voltage of 1.7V but then goes down to 0,46V.
It seems that turns off for heating the CPU while the CPU is in fact still cold.
Any suggestions?
Thanks in advance

Check all the voltages, maybe need to reprogramm BIOS flash.

Thanks for the reply. From what little remains on the PC, the tensions are all there. Sometimes I can also access the bios but then immediately turns off. Maybe it was damaged the PU4201 due to short circuit of the PU4302. I'm waiting for the replacement of PU4201.
Hopefully where I could find the file of the bios of this model?

Dear friends I wanted to share with you the resolution of the problem. The problem was the PU4201. I replaced it and the pc works now.
Thank you all for your attention.