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So I was about to benchmark cooling techniques to cool my raspberries when I noticed that my RPI3B Rev 1.2 board was getting abnormally hot out of the box when booting a vanilla Raspbian from the SD card.

Specifically the Broadcom BCM43438 WiFi chip, the micro SD card reader and the SoC was getting hot under 10 seconds of powering the board, out of these 3 the WiFi chip being the hottest, couldnt keep my finger on it after 3 seconds from powering the board with an bootable SD card present.

An interesting thing is that I found that the heating issue only presented itself when the sd card contains a bootable OS. What is interesting that even though there is clearly something wrong with the WiFi chip, the PI boots up fine and I am able to use WiFi to SSH, however out of fear of frying something I shut down the system. DMESG says nothing, except that undervoltage was detected (lol). The polyfuse is normal to the touch.

TLDR: WiFI chip and SD card reader are untouchably hot after 10 seconds of powering up my Pi, what could the cause be, how could I diagnose?

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    What temperature is it running at 'vcgencmd measure_temp'?
    – CoderMike
    Aug 25, 2022 at 15:24
  • It said something around 60C which is normal I guess after boot, as I said in the post, the WiFi chip is what I am more concerned about. Aug 25, 2022 at 22:16

3 Answers 3

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Untouchably hot is not good unless you are really sensitive ;) Unfortunately I think it implies damaged hardware.

I found that the heating issue only presented itself when the sd card contains a bootable OS

The problem might not show itself without that, since this includes firmware to spin up the SoC, and the Wifi might not even be powered.

Try to get a vcgencmd measure_temp reading to verify the problem, as Coder Mike suggested. Also try to have a look at top (I think it is part of the base install) and see what the load average is, and if there are any processes cranking the cores all the way up. If there isn't, and this is happening consistently, most likely the Pi is wrecked.

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  • You are likely correct with the WiFi chip not powered yet, that is why its not hot when no SD card is present. As I am afraid to power the board to prevent damage eversince I felt the radiating heat from centimeters away, I am unable to run the top command, but I am sure its not a process as it is a vanilla raspbian install using the imager, and my other rapsi does not have this issue, therefore I too suspect a hardware failure. The SoC was about 60C after booting which I am now sure is acceptable, however the WiFi chip was definitely over normal temp. Couldn't measure it with any tool though. Aug 25, 2022 at 22:25
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So after some digging around, I found a YouTube video, How to fix a Raspberry Pi 3 where the wifi chip is overheating, where the person described my problem pretty closely, and looking at the comments I am not alone with the issue. The WiFi chip was getting super hot after powering, and his solution was to desolder the WiFi chip completely.

I desoldered the Broadcom chip, and my overheating is gone, I don't know the exact cause but this way I can actually use this board, now the SD card reader the SoC is normal temperature as well, and everything works (except BT and WiFi of course :D ).

The video mentioned a possible short circuit or physical damage as a cause within the chip itself.

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  • Good show! +1 Hope your warranty covers this.
    – Seamus
    Aug 28, 2022 at 16:14
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Welcome Dominik. Sorry but as I understand it is a defective Pi. If it is new you can try for warranty replacement. If you have modified the board in any way the warranty would be void. I recommend you do this before you smoke something. Contact the vendor and follow their procedure. You purchased in good faith. As a last resort you can remove the bad chip but probably better just do not turn it on.

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