63854
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Rasberry pi's c6 capacitor has been getting unusually warm.

Tue Jun 11, 2013 6:13 pm

A few weeks ago I dropped my raspberry pi and since then the c6 capacitor on it has been getting very warm when there is power coming into it. The raspberry pi still functions normally, and the only damage it sustained was a dent in the Ethernet port. Any ideas of what happened to it and is it safe to use?

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redhawk
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 7:07 pm

Capacitors are not know for getting warm they can, however they do have the characteristics of bulging with possible discharge though.

Are you sure the heat isn't coming from the RG2 regulator D17 on the underside??

Richard S.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 7:19 pm

Yes, the heat does seem to be coming from D17 and RG2, so should I be worried about that?

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redhawk
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 8:29 pm

What PSU rating are you using??

Do you have a digital volt meter to check if the voltage at TP1/TP2 is within spec??

Richard S

63854
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 8:35 pm

I'm new to the raspberry pi, so I don't know what PSU is, and I don't have a digital volt meter. :P So the components are warm when the raspberry is halted, and then they must get REALLY hot because the capacitor becomes hotter than the processor. :cry:

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redhawk
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 8:44 pm

PSU = power supply unit. :)
D17 is a transient voltage suppressor diode it's designed to prevents harmful voltage spikes coming from the power supply.
It will also conduct (and short circuit) if the voltage input gets too high i.e. 5.8v, 6v, 7.5v which is probably why it's getting warm.
I would advise you to measure the output voltage or at the very least change the PSU for another one rated 5v @ 1A and regulated.

Richard S.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 8:49 pm

My power supply is 1 amp and 5v, (I checked the old phone charger I was using), but the power supply is plugged into a power strip with about 5 other things plugged into it. Is it possible a device plugged into the power strip is responsible for my issue?

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redhawk
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 9:00 pm

The problem with old phone charges they tend to be unregulated so a 5v output could in fact be as high as 6.5v instead.
Since the phone has a regulator and charging circuit built in there's no real need for manufacturers to provide a PSU with accurate voltage output as long as it's high enough for the phone.

Do you have a make and model number for your power supply??

Richard S.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 9:04 pm

Yes, my power supply is an HTC phone charger model TC U250

The manufacturer is Emerson Network Power.

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redhawk
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 9:27 pm

Well as a HTC product you would expect quality but just to be on safe side you should get the voltage output measured with a digital voltmeter.

Are you using an externally powered USB hub by any chance??

Richard S.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 9:46 pm

Yes, I am using a Belkin brand powered USB hub model F4U022v.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Tue Jun 11, 2013 9:48 pm

An elco (electrolytic capacitor) such as C6 normally does not produce heat itself, with one exception, and that is when there isn't a clean DC coming in from the power supply, but instead there is a large ripple on the DC, which the capacitor tries to "smooth out", by constantly taking in current, and then releasing it. This causes energy losses in the cap itself which heats it up.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Wed Jun 12, 2013 1:11 am

I used a different power supply and D17 is still getting hot, so I'm guessing this is normal. Does D17 usually generate heat?

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Wed Jun 12, 2013 10:16 am

No! D17 is the over-voltage protection diode, and is normally completely inert unless you try to put more than six volt on the micro-USB port, (on the 5V line) then it will short the 5V line to protect the PI, this would normally blow the fuse and so prevent further damage. After you remove power the diode stops shorting, and after you wait for the polyfuse to recover your PI should work again.

But If you bypass the fuse somehow, (powering the PI over the GPIO header, or the USB port on the back) then D17 may become damaged as there is nothing preventing D17 to burn out!

Are you sure it is D17 that is generating the heat?

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redhawk
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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Wed Jun 12, 2013 10:22 am

Could you test the Pi without the USB hub just in case it's back feeding more than 5v into the Pi.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Wed Jun 12, 2013 4:25 pm

Seems like DG2, D17, and c6 are all warm. I have one of the newer raspberry pi's made in China, so I'm not surprised if the board is faulty. :x Also I've heard that DG2 gives 1/3 of its energy off as heat, so the other components may just be hot do to the radiating warmth. Does every pi get at least some heat in the DG2 area? Also I've tried my pi with an unpowered USB hub (I unplugged the transformer that went into powered USB hub) and got the same results.

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Re: Rasberry pi's c6 capacitor has been getting unusually wa

Thu Jun 13, 2013 7:33 pm

63854 wrote:Seems like RG2, D17, and C6 are all warm. I have one of the newer raspberry pi's made in China, so I'm not surprised if the board is faulty. :x Also I've heard that RG2 gives 1/3 of its energy off as heat, so the other components may just be hot do to the radiating warmth. Does every pi get at least some heat in the RG2 area? Also I've tried my pi with an unpowered USB hub (I unplugged the transformer that went into powered USB hub) and got the same results.
RG2 does get hot, as will any linear regulator. Yes, it's discarding 1/3 of its input power as heat. Some of that heat is radiated through its case, but I think most of it conducts to the PC board so it warms up all components in the immediate area.

How hot does C6 get? If it's just warm, i.e., you can leave your finger on it indefinitely, no problem. If it's hot, e.g., you have to take your finger away in less than 2 seconds, it could be a problem. If an electrolytic capacitor gets hot its electrolyte boils away and the capacitor either becomes an open circuit or shorts out.

A lot depends on what kind of case you have. When I first had my RasPi, it was sitting on an anti-static bag. There was no air flow underneath and the back side got very hot. I now mount my RasPi vertically, so there's passive air flow on both sides and it runs at most warm.

There are some nice thermal images of a RasPi model B rev 1.0 at this Spanish site: http://www.geektopia.es/es/technology/2 ... iento.html
The images are color-coded, and you can see that RG2 gets quite hot. There's a Celsius temperature scale on the side of most images. C6 gets warm. It's not hot like RG2 (which may burn your finger-tip after a second or two) or really hot like the LAN9512 (rev 1.0 had a PCB error that caused some LAN chips to run much hotter than they do on rev 2.0). However, C6 does get warmer than most of the connectors.

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