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Odd One: 820-00923, Won't Boot to External on 2 Ports

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    Odd One: 820-00923, Won't Boot to External on 2 Ports

    We got a really weird one in the shop last week and I've just been trying to figure out exactly what could cause the issue's we're experiencing. The symptoms are odd:

    820-00923, no liquid, no damage, not previously-repaired, etc.

    1. Unit powers up and boots fine; passes AHT, SSDs wipe/install OS perfectly fine, unit will run for hours under stress, and charge/discharge totally fine from ALL four ports. No issues until...

    2. You try to boot to an external drive (OS installer or bootable drive, doesn't matter) using ONLY the "bottom" port on each side of the unit. Board boots perfectly fine to external drives on both "top" ports--both orientations; no issues. Issue only occurs on each "bottom" port--both cable orientations. When you try to boot to external using the bottom ports, roughly 30% into the loading progress bar, the board throws the prohibitory sign (circle/line through it). The behavior is *exactly* the same, every single time.

    3. Also, to add to the strangeness, the unit does detect USB devices and drives in the problematic ports just fine, so the power supply for the CD3215s seem fine (typically we would not see any USB device detected when those fail), but to be sure, I replaced them anyway--same problem.

    4. Performed clean install, new BIOS, etc., same issue.

    5. Issue exactly the same across 3 different test-cases with 3 sets of USB-C port assemblies, etc.

    Every single time I've EVER encountered the prohibitory sign, it's always ended up being a no-fix (PCH was consensus on several occassions). But, those boards typically had much more significant failures accompanying the sign. In this case, I'm hopeful we "may" find the issue/cause because the boards works so well in every other way. We've combed over the entire board several times and found zero damage.

    Really stumped on this one! Hoping we aren't looking at a PCH or CPU issue. Curious to hear any thoughts!
    Last edited by ugamazing; 04-21-2022, 11:09 AM.

    #2
    Re: Odd One: 820-00923, Won't Boot to External on 2 Ports

    Just bumping this in case anyone has any ideas?

    Comment


      #3
      Re: Odd One: 820-00923, Won't Boot to External on 2 Ports

      Remove all power. Meter in diode mode.

      Red meter lead (yes, Red) to ground.

      Black meter lead to D+ on the good port. What is the reading?

      Repeat for D- pin. Post the readings.

      Now repeat for the non-working ports.

      Most likely an ESD transient has damaged the clamp diodes on the non-working ports. They are often 0201 tinny buggers but very cheap and very common to source.

      Let us review the diode readings of the usb signals to compare.

      Comment


        #4
        Re: Odd One: 820-00923, Won't Boot to External on 2 Ports

        Thank you for the reply--I had given up hope on this one! I have compared diode readings across all ports and they are all within range, nothing sticks out.

        I'll go back over things again and see and will update! Thanks again for the reply.

        Comment


          #5
          Re: Odd One: 820-00923, Won't Boot to External on 2 Ports

          Originally posted by mon2 View Post
          Remove all power. Meter in diode mode.

          Red meter lead (yes, Red) to ground.

          Black meter lead to D+ on the good port. What is the reading?

          Repeat for D- pin. Post the readings.

          Now repeat for the non-working ports.

          Most likely an ESD transient has damaged the clamp diodes on the non-working ports. They are often 0201 tinny buggers but very cheap and very common to source.

          Let us review the diode readings of the usb signals to compare.
          Forgive me, but what exactly do you mean by "D+" and "D-"? I'm not familiar with that particular jargon when working on these, my apologies.

          Comment


            #6
            Re: Odd One: 820-00923, Won't Boot to External on 2 Ports

            Review the connector @ J3300. Remove all power.

            Meter in diode mode.

            Red meter probe to GROUND.

            Black meter probe to test pin 1 of this connector. Measure the reading.

            Then continue to measure the rest of the unique pins on J3300. You can skip ground since that is a known value.

            We are checking for possible damaged ESD diodes which is a common fault.

            Then repeat the above exercise with the next USB-C connector block @ JB500 for the same investigation.

            Post each reading.

            D+ / D- are common to USB connectors and are the differential signals used by the USB communication components. By review the above, all USB-C connector pins will be measured (including D+ / D-).
            Last edited by mon2; 05-18-2022, 09:55 AM.

            Comment


              #7
              Re: Odd One: 820-00923, Won't Boot to External on 2 Ports

              Thank you! Yeah I know all about diode mode, checking drop-off between circuits/ground and all that, I just didn't know specifically what "D+" and "D-" referred to, as I don't see any reference to those indicators in the schematics. Thinking now you may just be referring to the lines with the diodes in place, etc.

              I'll go through and check all the pins again--I have a sheet where I've done this already and didn't find anything anomalous, but there must be something there. I'll focus more on the ESD diode lines in particular.

              Thanks, Mon!

              P.S. Weren't you on the old Advanced Reworks forum? Possible "Gurmon"? I think I remember talking with you a bunch back in those days.

              Comment

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