Raspberry Pi B+ won't boot (no red light)

[Antonio92]

Hello,

I have been using my Raspberry Pi B+ for four days and today it shut down and now it does not boot, it seems it does not receive any power as there is no led turned on (neither red nor green). I was playing with a project manipulating the GPIO pins when it shut down, so I think i might have done a short circuit or something.

Although there is no led turned on, the main chip the one next to the Raspberry logo on the board[/img]) gets very hot once I plug the Raspberry in, and the voltage between test points PP1 and PP3 is between 4.98 and 5.02 V, and the voltage between both sides of fuse F1 is 0.00 V.

At the moment I plug the raspberry in, though there are no leds on as I say, the low buzz the Raspberry always sends out when working, sounds for a while (2 secs) and then stops and the chip I wrote about begins to heat.

What can be happening?

Thanks

[mahjongg]

your manipulations with the GPIO have caused both transistors in one of the GPIO drivers to break down, and they are now causing a short inside the SoC, between 3V3 and GND. The reason is that initially one transistor broke, because of a short, (or an over voltage on the pin) causing the transistor to burn out, and turn on permanently, when the other transistor is also turns on, a short circuit current runs through both transistors, burring out the other transistor too.



In short you PI is defective, and irreparably so.

[drgeoff]

No argument with mahjongg's words, but his diagram shows bipolar transistors, not the CMOS devices that the Broadcom chip uses.

[mahjongg]

yeah, I did a quick search for a suitable picture, but could not readily find a "totem pole" with mosFETs, and as I talked about "transistors" I thought it would not matter much as an illustration of the principle.

here is a better picture:

[Antonio92]

I thought it would be recovered after a few days, as I have seen that sometimes polyfuses recover after some hours of days. Then realised than the GPIO pins are not protected and they have nothing to do with the polyfuse. At this time I have ordered a new Pi. Thank you for your answers.