Strange behavior of charging ic ISL88738H

Collapse
X
 
  • Time
  • Show
Clear All
new posts
  • linhtinh
    Member
    • Sep 2020
    • 28
    • thailand

    #1

    Strange behavior of charging ic ISL88738H

    Dell LA-H331P board.

    Schematic here
    Boardview exactly same la-f541p here

    First is the ISL88738H charging ic died, i replaced it but the PQ1900+PQ1902 mosfets kept dying, all mosfets are taken from the donor board.
    Strange behavior is the machine still turns on without battery, i can still enter into bios, but when I pluggin the battery it doesn't charge.
    I measured all the capacitors and resistors around the charging ic, all are normal. Does anyone know why the PQ1900/1902 mosfets keep dying (shorted D-S) ?​
  • mon2
    Badcaps Legend
    • Dec 2019
    • 13866
    • Canada

    #2
    1) Check if any of the other mosfets on this charger IC is shorted / leaky. Are you sure that the PQ1900/1902 mosfets are being soldered in the correct orientation for pin # 1? They are 100% the same mosfet as the original? Share the part number of the mosfet(s) that are dying. Post pics of the reworked area for these replaced parts.

    2) Confirm that the ISL88738 IC is soldered properly and without shorts.

    3) If the battery does not charge, confirm the battery is not defective. This is a DELL so the PSID communication on the DCin power connector is very important. Attach your power adapter and measure the voltage to ground of the PSID pin # 4 of the DCin power connector.

    Post the measurement. Without this 1-wire communication line, the logic board assumes the power adapter is underrated and will not charge the battery.

    Comment

    Related Topics

    Collapse

    • Scoff
      HP Probook 470 G4 - Power and Charging Problem
      by Scoff
      Looking for some help with this one if anybody can assist please? I have an HP Probook 470 G4 Laptop which recently started to intermittently failing to turn on, with intermittent white LED light(charging LED) by the charging port when it should have been charging and showing an orange LED instead. Definitely some sort of gradual failure. Now the laptop fails to power on at all, no charging LED, no Power Button LED either - seemingly dead.
      Stripped down to the bare motherboard. The original HP battery, when disconnected from the motherboard, is reading 0.00v - possibly some sort of protection...
      07-03-2023, 09:28 AM
    • flat-earther
      ASUS X54H laptop thinks it's always charging even with charger unplugged
      by flat-earther
      The charging indicator light on my ASUS X54H laptop is always on even when the charger is disconnected.

      Windows also shows ''Plugged in'' when charger is not connected.

      This problem started year ago gradually, when unplugging the charger the charging light took several seconds to disappear, then minutes, and now almost always on even when unplugged for an entire day.
      Strangely, before sometimes immediately when plugging in the charger the charging light went away, and later came back with it connected.
      If I let battery run out and say it has 3% Windows will...
      06-24-2025, 09:32 AM
    • CPUFiddler
      Acer Nitro 5 AN515-45 not charging
      by CPUFiddler
      Hi there. I am trying to repair an Acer Nitro 5 AN515-45 and it's giving me some trouble. I have access to SMD rework station, variable power supply, digital oscilloscope, thermal camera, multimeter, stereo microscope.
      This laptop will boot and run from the power brick and/or the internal battery, but it will not charge the battery. NirSoft BattInfo tells me the charge/discharge currents, so I'm confident in saying that it's not charging. In addition, there's no increase in voltage at the battery connector when the laptop thinks it's charging, not even a few millivolts.
      I've downloaded...
      03-19-2025, 07:44 AM
    • Julian Bailey
      HP ProBook 445 G8 Battery not charging
      by Julian Bailey
      Hi all

      We have in a HP ProBook 445 G8 laptop with AMD Ryzen 7 CPU. When power is connected the power LED light blinks 5 times then stops. Normally HP laptops will blink this LED 10 times as it does a self test when the AC adaptor is inserted. So there must be some sort of short somewhere.

      The battery doesn't charge, and is erratic on the MM voltage. Bench PSU LED pulsates when the battery is connected also. So the fault must be on the charging circuit?

      I have gone around the board with a MM and cant find anything

      Windows shows the battery fine,...
      10-11-2024, 10:34 AM
    • BlackScreen_22
      Harman Kardon sub TS11 (ds15 amplifer) blows fuse and mosfets
      by BlackScreen_22
      Hi, I'll start by saying that I'm not an expert and I've reached a point where I don't know what to try/do anymore...
      Starting from the beginning: I opened this subwoofer for the first time with a very strong smell of burnt electrical components, I realize that on the amplifier board there is a hole between V+ OUT and GND about the size of a finger, the damaged components were the shorted mosfets, two damaged zener diodes and two capacitors. I bought everything, I fixed the hole by cutting the pcb and putting a piece of a perforated board.
      I had no problems connecting mosfets and capacitors,...
      08-27-2024, 12:46 PM
    • Loading...
    • No more items.
    Working...