I have burned the IC U2

  • Hello, I was testing the duet wifi and I accidentally made a short with the tip of the multimeter and I think I burned the board. Apparently the IC U2 has been burned and I would like to know if it can be easily obtained or if it can be replaced by another more common reference. 0_1548354473753_WhatsApp Image 2019-01-24 at 1.24.02 PM.jpeg

    Thank you in advantage

  • administrators

    U2 can be replaced, however when it blows like that the reason is usually that you have shorted either +3.3V or +5V to +24V; and that is likely to have damaged other components too, especially if the short was to +3.3V.

    You could remove U2 (you will need hot air rework equipment and a hotplate), then apply 3.3V between the +3.3V and ground pins on one of the endstop connectors. If that gets the USB port and WiFi working, and the main processor doesn't get hot, then it's likely that the board can be repaired. You could even try applying 3.3V without removing U2, but U2 may short it out.

    The part number for U2 depends on the PCB revision. Looking at the photo, I think you have a 1.04 board. The part number for that is AP7361C-33E-13. Do not get the version with an extra R in the part number.

  • @dc42 Hello, thanks for answering, I was testing the sd card and it seems that it has also been blown. I did the tests that you told me removing U2 and the wifi module heats up, the main processor gets hot but very little, I think the U2 was not the only thing I blew.

  • administrators

    If the SD card is blown, that is a good indication that there was excessive voltage on the +3.3v rail. If the excessive voltage was only +5V then there is a chance that not many components have failed.

    It's normal for the main processor to get a little warm. Are you able to connect to it via USB? If not, try putting a jumper over the Erase pins to erase the firmware, then remove it, reset the board, and see if the Bossa port appears on your PC. I think at least one user found that excessive voltage on +3.3v had corrupted the firmware, but was able to re-install it.

  • @dc42 hello, I've done everything you said and the Bossa port does not appear on my pc and strangely I just connect Vin, the Duet turns the hot bed out. I think the short was between these two terminals:0_1548542915536_InkedWifi_v1.04_above_wb_small-800x800_LI.jpg

  • administrators

    That would be a short between V_FAN (which you have set to VIN, so +12V or +24V) and +5V. That's blown the 3.3V regulator U2 and subjected multiple 3.3V components to excessive voltage. Sadly, the board is probably beyond economic repair.

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