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USB ML Universal RevB: Accidentally applied 12vdc to BDM cable
Darrin K. Oct 19, 2016 at 01:23 PM (13:23 hours)
Staff: Johnny N.

  • Accidentally plugged the ML HC12 BDM cable into a board that turned out was accidentally running at 12v instead of 5v.
    The ML Universal worked for a while (after I caught the problem), but now the Yellow light will not come on.

    Do you know what components would need to be replaced when 12vdc was applied to JP1 of the USB ML Universal Rev B?
    I have a second working USB ML Universal Rev B to compare to and none of the resistors are bad.
    But it looks like JP1 connects to U4 DG411DY, U24, U9, U23, T3
    Can you give me the part#'s for these designators? Is there a schematic I can download?



    • Hi Darrin,

      If the yellow LED no longer turns on then there is a problem with either the voltage detection circuitry or the main MCU. I can provide some part numbers for the ICs that can be replaced. If the main MCU has been damaged, then the multlink cannot be repaired and you will need to purchase a replacement.

      T2,T3 Fairchild 1N752A_T50R; 1N5232B

      Voltage Detection:
      U5 National LMV7239M5/NOPB

      P&E Engineering Support

      • Goodmorning,
        I didn't used to connect power supply directly to the MCU, always pass through a linear regulator, but this time I tried, when I turned off the laboratory power supply I got a overvoltage I burned the zener T3 of the USB_MULTILINK UNIVERSAL rev B and the MCU, I disconnect T3 and everytinghs works, It's possible that was that the problem?

        It is possibile to replace T3 for example with BZX79-C5V6,113
        or any other 0,5 W 5,6 V zener? It is safe or it's better 1N5232B as you said.

        Thank you

        • Hi Marco,

          It sounds like the diode was the only issue on your multilink then. The 1N5232B is 5.6 V and 500 mW so I think the one in your link will be fine.


  • FYI for anyone in the same situation: Found the problem.

    U24 c665 was blown (which is connected to the BDM +5v line.
    sn74lvc1g66 analog switch blown open.

    we are all good now.

    • Great, glad you were able to repair it.

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