Toshiba C70-B charging troubles

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  • mr_grey_hat
    New Member
    • Apr 2019
    • 4
    • Turkey

    #1

    Toshiba C70-B charging troubles

    I have a Toshiba Satellite C70-B (Motherboard AR10SU-6050A2631701-MB-A01) with, I presume, issues with its charging circuit. I had a dead battery for a long while and had to keep the AC connected to be able to use it. I decided to finally replace the battery, but the replacements are not working. The amber power LED blinks repeatedly and the laptop refuses to start. I tried multiple replacement batteries, they all show the same behaviour.

    Here is what I know so far:

    AC only - OK. Power LED burns white and laptop boots.
    AC + dead battery - OK. Power LED burns white and laptop boots. After a while, the LED starts blinking amber, but I can keep using it. If I turn off the laptop while LED blinking, laptop won't start until AC disconnected and reconnected.

    New battery - Power LED blinking amber. Doesn't start
    AC + New battery - Power LED blinking amber. Doesn't start

    When I boot with AC only and then connect the new battery, power LED turns from white to amber (blinking), OS shows 60% charge but 0 charging current. If I then unplug the AC, laptop shuts down.

    As I tried multiple replacement batteries, and they all behave the same, I opened up the laptop and took some measurements of the charging IC BQ24735 (see attachments). Nothing really jumped out at me, other than BTST not being Vbat+6V when new battery + AC connected, but I have no idea why this is the case. I also found it odd that on the new battery, BATDRV is high and I see VCC on the SYSTEM output, meaning the laptop should be working but doesn't?

    Any ideas on how to proceed? Is the charging IC faulty, a short somewhere around it or an issue with current sensing resistors? Also, I was unable to find a board view or schematic for this board, so if anyone could share, that would also be very helpful.

    Thanks in advance!
    Attached Files
  • mon2
    Badcaps Legend
    • Dec 2019
    • 14086
    • Canada

    #2
    Re: Toshiba C70-B charging troubles

    1) Power down, remove the battery.

    2) Meter in resistance mode (200 ohms). Check the resistance for each and every mosfet linked to this charger IC for possible shorts.

    Resistance between SOURCE & DRAIN ?

    Resistance between SOURCE & GATE ?

    Resistance between GATE & DRAIN ?

    Repeat this for all 4 mosfets linked to this IC.

    As a comparison to a similar charger IC device, review the posted chart by @DanielDacko here:

    https://www.badcaps.net/forum/showthread.php?t=98587

    Comment

    • mr_grey_hat
      New Member
      • Apr 2019
      • 4
      • Turkey

      #3
      Re: Toshiba C70-B charging troubles

      I measured all 5 mosfets going to the IC at 200ohms mode. ACFET, RBFET, BATFET, LODRV and HIDRV all show open line between S&D, S&G and G&D, so no shorts there.

      I also checked the diodes, capacitors and resistors around the area, no shorts to ground. Resistor values seem good, except the 2 R020 resistors showing 0.3Ohm instead of 20mOhm, but I don't really have precision equipment to measure those. Diode between REGN and PHASE also okay.

      Comment

      • mon2
        Badcaps Legend
        • Dec 2019
        • 14086
        • Canada

        #4
        Re: Toshiba C70-B charging troubles

        Review this thread in the meantime for other ideas:

        https://www.badcaps.net/forum/showthread.php?t=90356

        Comment

        • viking6791
          Member
          • Aug 2018
          • 40
          • My Desk

          #5
          Re: Toshiba C70-B charging troubles

          Hello all, I have the same defect on my Toshiba C70-B (AR10SU). I tried to solve this issue with a clean ME region but without success.
          I changed BQ735 and 3 mos transistors on charging circuit before clean ME.
          The battery is new and fully charged on other laptop.
          I need schematic or some guidance to repair this laptop.

          Thanks in advance!

          Comment

          • viking6791
            Member
            • Aug 2018
            • 40
            • My Desk

            #6
            Re: Toshiba C70-B charging troubles

            My problems was the new battery, now I wait tools for repairing battery.

            Comment

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