portets
Posts: 186
Joined: Sat Oct 29, 2011 6:24 am

Re: Brand new rPi + bad F3 polyfuse

Mon Jun 24, 2013 9:37 pm

If that circuit is wired how I think it is, you weren't supposed to short the diode with a wire after removal. I think you just wired positive to negative directly.

Hopefully your power supply has short circuit protection.

drgeoff
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Re: Brand new rPi + bad F3 polyfuse

Mon Jun 24, 2013 9:47 pm

Removing D17 is not the same thing as replacing it with a piece of wire!

D17 is between 5 volts (after the polyfuse where not bypassed) and ground. You have put a short circuit across your PSU. No surprise you measure 0 volts everywhere.

thsBavR10
Posts: 233
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Re: Brand new rPi + bad F3 polyfuse

Tue Jun 25, 2013 7:19 am

0V is correct! Why?
You have shorted the power supply by bridging D17.
Have a look at the schematics: http://www.raspberrypi.org/wp-content/u ... s-R1.0.pdf
Remove the bridge at D17! Maybe your power supply survived the shortage ...
Probably your power supply does not provide the correct voltage.

Edit: others were already faster...

FrTedCrilly
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Re: Brand new rPi + bad F3 polyfuse

Sun Jun 30, 2013 10:29 pm

Hi,

Sorry got distracted putting the fire out on the Pi :-) kiddin.
yea the psu caught the short circuit and all is ok.
I have removed the wire and now the capicator is now getting very hot seconds after Plug it in.
there is a steady 4.75v across tp1 and tp2.
is this ready for recycling ?

Thanks for the help
T

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mahjongg
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Re: Brand new rPi + bad F3 polyfuse

Mon Jul 01, 2013 12:22 am

if the capacitor is getting hot it is defective, but is it the capacitor that generates the heat?

The capacitor (round silver, with printing "220" on it) isn't strictly necessary, some people manage to break it off the board by putting pressure on it while pulling out the power cable. In most cases the PI still works without it. It just reduces ripple coming from the PSU.

FrTedCrilly
Posts: 12
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Re: Brand new rPi + bad F3 polyfuse

Mon Jul 01, 2013 9:16 pm

hi mahjongg,

You are quite correct, it is not the capacitor its the voltage regulator. its heating up so hot is not bearable to touch after 5 seconds.
What could be causing this. Thanks for you help so far as I am lost without your help

Thanks
T

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mahjongg
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Re: Brand new rPi + bad F3 polyfuse

Tue Jul 02, 2013 6:15 pm

FrTedCrilly wrote:hi mahjongg,

You are quite correct, it is not the capacitor its the voltage regulator. its heating up so hot is not bearable to touch after 5 seconds.
What could be causing this. Thanks for you help so far as I am lost without your help

Thanks
T
What may cause it is a current overload, or in other words a shorted output!

This is a voltage regulator that converts 5V to 3,3V, and it dissipates (turns into heat) the difference. The more current runs through it the hotter it gets, if its extremely hot that probably means the output is shorted.

I can only assume you PI has a short, and it could be very costly, or even impossible to repair!

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