echo21
Posts: 13
Joined: Mon May 28, 2012 12:04 pm

Broke a component off the board

Mon Jun 25, 2012 11:23 am

Hi,

Whilst plugging the power cable into my Pi, I managed to break one of the capacitors off the board - C14. looking at the schematics, it's part of the HDMI circuit.

The Pi seems to work OK without it, HDMI still works - I use it headless so I wouldn't be too bothered if it didn't.

Does anyone with electronics experience know what this capacitor is used for?

By the way, The Pi was in a PiHouse and it was one of the acrylic posts that sliced the component off!

Jim.

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AndrewS
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Re: Broke a component off the board

Mon Jun 25, 2012 11:31 am

Looks like it's part of the HDMI HotPlugDetect circuitry that allows the Pi to tell whether an HDMI lead is connected or not. Not sure what impact not having the capacitor makes though :?

echo21
Posts: 13
Joined: Mon May 28, 2012 12:04 pm

Re: Broke a component off the board

Mon Jun 25, 2012 11:36 am

I do have hdmi_force_hotplug=1 in my config file - I wonder if it's still working because of that?

Not sure if I want to test that theory in case I release the magic smoke. :D

Chris_Reynolds
Posts: 72
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Re: Broke a component off the board

Mon Jun 25, 2012 12:18 pm

There's a section in the wiki all about it. Look at the part about Capacitor C6 at the bottom of this page:

http://elinux.org/RPi_Hardware#Power

hope that helps you.

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AndrewS
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Re: Broke a component off the board

Mon Jun 25, 2012 12:21 pm

Capacitor C6 is very different to capacitor C14 ;) :P

Chris_Reynolds
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Re: Broke a component off the board

Mon Jun 25, 2012 12:24 pm

Whoops - my mistake - should read more carefully!

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Burngate
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Re: Broke a component off the board

Mon Jun 25, 2012 4:07 pm

By the look of it, it merely slows down edges on the hot-plug line, i.e. reduces noise susc ... sus ... increases noise immunity. 47k and 1n0 gives 47us on my calculator, or ~7kHz, so it's removing stuff above that. If you don't use HDMI, the Pi might randomly think you've plugged it in.

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Gert van Loo
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Re: Broke a component off the board

Mon Jun 25, 2012 4:47 pm

Without capacitor you can have false detects in the HDMI hot plug detect due to noise on the wire.

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