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Background:

I had Raspbian 10 (installed over NOOB) running on a Raspberry Pi 3B+ running:

  1. BOINC (30% CPU time and 25% CPU cores used)
  2. dump1090
  3. Kodi
  4. Kismet

since July 2020, pretty much 24/7 till December 2021. The typical load on the device was around 50% for all things combined. And the temperature hardly ever wandered above 43~44°C. There was a small 3.3v fan plus the usual heat sinks for the casing. For network an ethernet connection was used.

What changed recently:

Then 2 weeks ago, while updating the Pi I realized that there is a new version of Raspbian out. I set about installing a fresh copy of the Raspbian 11 on the SD card and decided to "upgrade" from NOOB to PINN.

New Setup:

I did not have the time to setup all things, but the following was up and running again:

  1. Boinc (30% CPU time and 25% CPU cores used).

And the rest I thought I could setup later over the holidays.

What was observed:

  1. A couple of days later however I noticed, there was no display coming over HDMI to the TV from the Pi.
  2. I could still remotely login over ssh and all seemed fine,
  3. except the CPU and GPU temperatures were both around 78°C !!!
  4. I shut off BOINC but the temperature hardly changed.
  5. Rebooting changed nothing.
  6. Interestingly, I noticed, if I booted the Pi with the HDMI cable plugged in, the cooling fan would not run now. Removed the HDMI cable again and the fan started.

Anyways, to cut the long story short, I reconned maybe during cleaning or something, I accidentally dropped something, something shorted or whatever. Time to buy a new Raspberry Pi, which amazingly despite being sold out nearly everywhere was luckily still found from one authorized raspberry pi handler and even arrived on 24th December.

2nd Raspberry Pi:

  1. The setup was the same, except no fan (as the casing was different). Just the heat sinks were fixed and the Pi was up and running with the same SD Card with the new Raspbian over PINN.
  2. I checked the temperature. It was 50°C~59°C. A little on the warm side. BOINC had minimal effect on the temperature. But I thought it's probably the lack of fan ventilation.
  3. Six days later, i.e. today, just to check, I logged in over SSH to see everything was going fine. The temperature was 70°C again!
  4. I turned on the TV and here again there was no "signal output" on the HDMI.

Result:

So, that's two dead HDMIs on two Raspberry Pis. Both still work in headless mode with the "only" downside being at a temperature of 70°C or more!

Question:

Since the only thing that changed was Raspbian 10 to 11, I am at loss to explain how it could result in hardware failure, on 2 different devices. That's already 90+€ down the drain.

Further Points worth mentioning:

  1. Since some people mention online that the GPIO interface can cause such problems, I want to add that from the raspi-config, I checked again, the GPIO Interface, the SPI Interface, the I2C Interface, etc all were off. Only things activated by me were SSH and VNC.

  2. Both Pis were ordered from (two different) authorized dealers (just by chance), ~3 years apart.

  3. The power supply should not be the issue, since I had already sorted out that problem last year.

  4. The room temperature is ~23°C.

UPDATE:

  1. I remember now, I did change the HDMI cable around Black Friday. The previous cable was too long. Could it be a bad HDMI cable overloading and damaging the HDMI port on the Raspberry Pis?
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    There is the possibility the monitor is damaged. If the HDMI still runs hot unplug the monitor and see if it cools down. If that works try a different HDMI cable, it is possible that failed and is placing an undo load on the pi.
    – Gil
    Dec 30, 2021 at 22:26
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    have you considered, for the sake of troubleshooting your issue and determining if the upgrade of the OS is at all an issue, "downgrading" back to Raspberry Pi OS Buster (it's still available as the so called "Legacy" image in Raspberry Pi Imager) - the Raspberry Pi Foundation truly screwed the pooch releasing a Bullseye seemingly before they tested at all
    – Bravo
    Dec 31, 2021 at 0:05
  • Thanks Gil and Bravo. The Pis run wildly hot without any external connections with just the Power Supply. The two heat sinks at the top are impossible to touch. That TV has a fire TV stick connected to one of the 3 HDMI ports and that works fine. I haave switched their places unknowingly many times without issue. Indeed, the 3rd Pi I would buy, I would run on Buster. Even PINN had an option for the "oldstable". I was blind to not have chosen it. Dec 31, 2021 at 7:42

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