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820-2530 ppbus .19 volts always stays green

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  • 820-2530 ppbus .19 volts always stays green

    I have an 820-2530 which is not turning on. I have 0.19 volts on ppbus with no short.

    The adapter light turns green and never changes to orange, does that indicate anything in particular?

    My only thought is isl6958, but I am not sure what enables I should be checking first
    Last edited by shanenin; 02-10-2019, 01:18 PM.

  • #2
    Post some voltages for ISL6258 (U7000), pins 2, 3, 19, 20, 12, 1, 14, 9, 15.
    Post exact resistance between pins 17/18 and 27/28.


    • #3
      thanks :-)

      of the 9 voltages you asked for I have 0v on all of them except 3.4v on pin 12 and 18.2v on pin 1

      17/18 20.7 ohms
      27/28 20.4 ohms

      on a side not the steady green light is gone

      edit added/

      I do have a 10 ohm short on r7011 or pins 3 and 19 or the isl
      Last edited by shanenin; 02-10-2019, 06:09 PM.


      • #4
        Looks like bad U7000; remove C7044 to confirm.

        Do you have short/low value on other pins of U7000?


        • #5
          of the 9 voltages (2, 3, 19, 20, 12, 1, 14, 9, 15) you asked for I have 0v on all of them except 3.4v on pin 12 and 18.2v on pin 1

          is this what you are asking?


          • #6
            I asked for short, or low resistance to ground.
            So chek in diode mode these pins...


            • #7
              I did switch the isl, and the short is gone between pins 3 and 19. The only voltage change is I now have 4.35v at pin 3. I still have the same voltages at 12 and 1. Do you still need me to check for shorts/lows on the other isl pins?


              • #8
                I bet D7010 is burnt; confirm and change it...


                • #9
                  thanks. I will try that tomorrow. Does that diode change the voltage or just work as a one-way valve?
                  Last edited by shanenin; 02-10-2019, 09:22 PM.


                  • #10
                    Just a protection for U7000.
                    Voltage drop on it is less than 0.5V...


                    • #11
                      Well, this was interesting. I switched out the diode and had a good ppbus of 12.6v. I think I still had other issues as it was not pulling hardly any amps. I was wondering about the missing green light on the charger and noticed one of the power pins was pushed in. So I grabbed an after marker charger which we have used for ages(we have gotten rid of all of them, expect this one was still laying around) to see if I would get the green light back, which I did. Then I was taking voltages for all of the isl6258 pins for future reference. Then I noticed it was no longer working anymore. D7010 is bad again. While measuring it I noticed the after marker charger is giving 18.9 volts, could this have been what caused it or just coincidence? I am leaning towards coincidence since something had to have killed D7010 before and it is likely the same thing. Should I track another diode down and try again?

                      edit added//
                      for replacement diodes, what things should I be looking for in the schematics so I can check donor boards?
                      Last edited by shanenin; 02-11-2019, 06:00 PM.


                      • #12
                        After D7010 is changed, don't power up the board before check for short or low value to ground on some pins of U7000; especially pin 2!!!
                        That diode is not critical; original is Schottky, but normal Si should work too.


                        • #13
                          is SI mean a silicone diode? Is the difference having a slightly greater voltage drop? Could you give any suggestions on what to search for in the schematic in regards to finding a replacement?
                          Last edited by shanenin; 02-12-2019, 12:12 PM.


                          • #14
                            1SS418, is not a critical diode
                            Silicon Epitaxial Schottky Barrier Type, 30V/100mA.


                            • #15
                              what do you mean it is not critical? Do you mean a different type of diode with a 100ma limit can be used or I can just use a jumper(probably not).


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