segunda-feira, 17 de dezembro de 2012

Replacing polyfuses of the Raspberry Pi



One of issues of Raspberry Pi is voltage drop over polyfuses.
To solve it, I replace F3 and F2 for some salvaged from a old PC main boards.


Original RPi USB ports polyfuses, 140mA each.

Power input polyfuse, 750mA

F3 polyfuse removed and PCB cleaned.

Polyfuse F2 removed and PCB cleaned.

Polyfuse F2 damaged when removed.



"New" 1600mA polyfuse installed on F3 position.

Original F3 750mA installed on F2 place.


IPAQ PSU 5V @ 2A
open: 5.11V


Voltage measurements before polyfuses replace:
USB PSU side: 5.05V
TP1 - TP2 : 4.64V
TP2 - F3 : 4.80V
F3 drop: 160mV
Cable loss: 250mV

After replace:
USB PSU side: 5.05V
TP1 - TP2 : 4.76V
TP2 - F3 :  4.81V
F3 drop: 50mV
Cable loss: 240mV

With USB HUB connected (no devices).
USB PSU side: 5.04V
TP1 - TP2 : 4.71V
TP2 - F3 :  4.77V
TP2 - F2: 4.71V, 4.68V
F2 drop: 30mV
F3 drop: 60mV
Cable loss: 270mV

One problem persist, voltage drop over cable. Can be solved powering Raspberry Pi from GPIO pins.


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