Power Problems

[kusti8]

This is a continuation of this thread since it got a little old while I waited for my new power supply. http://www.raspberrypi.org/forums/viewt ... 2&p=589267

When I plug in the raspberry pi with my new 2A 5V power supply, when running OpenELEC, the usb and keyboard start to work, but later fail to work. I assume that this is a problem with the raspberry pi, but when I use raspbian, the problems become less evident.
I am using a model B.
Any help is appreciated!

[redhawk]

When I plug in the raspberry pi with my new 2A 5V power supply, when running OpenELEC, the usb and keyboard start to work, but later fail to work

Is this during the user interface or does the screen go blank and you cannot wake it??

If you have a digital voltmeter then check the voltage at TP1/TP2 before and after the Pi becomes unresponsive.
If the voltage output appears lower than acceptable then you may have a poly fuse problem http://elinux.org/RPi_Hardware#Power_Supply_Problems

Richard S.

[drgeoff]

If your power supply is the type with a USB socket output and needs a separate USB to micro-USB cable, try another cable.

[kusti8]

The user interface shows and the wizard pops up but the mouse and keyboard are unusable and later the screen starts to dim. Already tested the TP1 and TP2 and the voltage was 4.65. Should I get a new raspberry pi or is there another cheaper remedy?

[drgeoff]

What voltage between one end of the F3 polyfuse and ground?

What voltage between the other end of the F3 polyfuse and ground?

[kusti8]

TP2 to SD card end of polyfuse is 5.19 V and the other side is also the same.

[kusti8]

Bump

[redhawk]

Could you measure TP1/TP2 again without the USB keyboard and mouse attached.

Richard S.

[kusti8]

Could you measure TP1/TP2 again without the USB keyboard and mouse attached.

Richard S.

Without any USB, the voltage is 4.45 V to 4.65 V

[redhawk]

Something is clearly wrong the voltage supply to the USB ports it's low and probably not sufficient to power the keyboard and mouse correctly.
In one of your posts you've measured TP2 with one end of the F3 polyfuse at 5.19v but TP1/TP2 was measured at 4.65v
So this would mean that there is a voltage drop of around 0.54v at both sides of the F3 polyfuse (measure to confirm this).
This is a considerable voltage drop for a Pi with no attached USB devices either the SoC is drawing more power than it's suppose to or the F3 polyfuse is going bad.

Back feeding power into the USB maybe one solution although not recommended without a stable regulated 5v supply.

Richard S.

[kusti8]

Is there any way I can repair this for a long term solution (not back powering) or should I just get a new raspberry pi?

[redhawk]

If you're good at soldering then I would try to replace the F3 polyfuse, or if you don't care then solder a wire link to bypass it.
The latter option would remove the Pi's protection from getting the wrong (high) voltage but at 5.19v I think you'll be fine.

Richard S.

[kusti8]

Where would I be able to buy a replacement for the polyfuse?

[drgeoff]

Where would I be able to buy a replacement for the polyfuse?

You told me earlier today:
"TP2 to SD card end of polyfuse is 5.19 V and the other side is also the same.".

Something doesn't stack up.

[kusti8]

Measured the polyfuse and sure enough, there is a 0.5 V difference. Sorry, not sure what happened the first time.

[kusti8]

Still, where could I buy such a fuse?

[redhawk]

Still, where could I buy such a fuse?

eBay is usually a good place to find electronic components i.e. http://www.ebay.co.uk/itm//141295599449? (there are SMD versions but they may not fit the board).

Richard S.

[mahjongg]

you need an 1812 size 1Amp to 2Amp polyfuse (PTC Resettable Fuse).

something like this:
http://nl.farnell.com/jsp/search/produc ... DP-1345925
or this
http://nl.farnell.com/littelfuse/1812l2 ... dp/1822216

make sure that when soldering the fuse to the board, you do it quickly, because overheating the fuse may damage it.

[kusti8]

Thank you! Will look into it.