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I'm trying to understand what happened to my MBP because it's a rather weird situation.

I hooked my MBP to a Samsung CJ89 43" monitor directly through USB type C. It worked for a while and then suddenly the built-in screen started flashing and then the connection to the monitor was lost. While connected, the laptop's fans were running hot but I didn't give it a thought, it usually gets hot even without it connected to a monitor since I run a lot of demanding tasks on it.

After this, I realised that the MBP won't charge anymore on any port. The right side ports wouldn't do anything, while the left side ports would still charge my phone, for example.

I used the original USB-C cable from Samsung, not anything cheap, so why did this happen?

I'm mainly asking because I got the laptop fixed but I'm afraid of hooking it back up to the monitor.

Ryncops
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Without putting hands on with the proper test and diagnostic equipment, there is absolutely no way to tell.

I used the original USB-C cable from Samsung, not anything cheap, so why did this happen?

Until you test the cable, you have no idea whether or not it's at fault. However, if you have any doubt as to the functionality and reliability of said cable, cut it in half (to prevent it from being used by others) and throw it away. Replace it with another from a known good, reputable brand.

  • This could have been a failure on your monitor's part - it just dumped way to much power into your Mac.

  • This could have been a failure on your Mac's part.

    • USB controller that negotiates power/charging died in some way
    • The SMC (and related circuitry) could have had a component failure

I'm mainly asking because I got the laptop fixed but I'm afraid of hooking it back up to the monitor.

If I had to guess, my money would be on the Mac failing and not your monitor. However, you can get a rather inexpensive USB-C power meter to "see" what your laptop's drawing and what your monitor (or other power source) is delivering. These run from $20 to $40USD online.

USB-C Power Meter

It's it "pro grade?" No. Those cost hundreds and would be way overkill for what you want. But it's "good enough." We're not looking to measure microvolts or check for negotiation packets. It will tell you, however, if something is majorly wrong so you can take preventative or corrective action.

Allan
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  • I was thinking about switching to a hdmi connection on the monitor and avoid charging the Mbp through the monitor. Is it possible to fry ports through hdmi? – Ryncops Jul 08 '20 at 20:50
  • You can fry ports through anything - just put too much voltage. But it doesn't matter because HDMI doesn't carry power for charging. That said...I still wouldn't use HDMI. It's flaky as hell and you'll get much better reliability from using DisplayPort – Allan Jul 08 '20 at 20:53