Announcement

Collapse
No announcement yet.

[HELP] Acer AN515-55 (LA-J871P Rev: 1B) – Board won't power on after GPU investigation – Suspecting Super I/O or PCH

Collapse
X
Collapse
 
  • Page of 1
  • Filter
  • Time
  • Show
Clear All
new posts
Previous template Next
    #1

    [HELP] Acer AN515-55 (LA-J871P Rev: 1B) – Board won't power on after GPU investigation – Suspecting Super I/O or PCH

    [HELP] Acer AN515-55 (LA-J871P Rev: 1B) – Board won't power on after GPU investigation – Suspecting Super I/O or PCH

    Hi everyone,

    I'm working on an Acer Nitro 5 unit with the following specs:
    • Motherboard: LA-J871P Rev: 1B
    • Model: Acer AN515-55-59MT
    • S/N: NHQ7JAL00403906A973400
    • SNID: 03902728734
    Initial Issue


    The laptop initially presented graphic issues and driver failure (Code 43) for the GPU.

    After preventive maintenance (cleaning, thermal paste, etc.), it powered on normally. We disassembled it again to inspect the GPU, reassembled for testing—it worked. Disassembled once more to show the client the GPU condition, and on the final reassembly (with no physical damage or errors), the board completely stopped powering on.
    Findings So Far
    • Super I/O was shorted. Replaced with a brand-new one (pre-programmed).
      → Short is gone, but the board still won't power on.
      → Power supply draws only 0.013A (13mA).
      → Pressing power button or shorting PWRBTN pads does nothing.
    • ON/OFFBTN# line shows 3V, and when shorted manually (or using keyboard), logic state changes → Super I/O receives the signal, but no reaction afterward.
    • Replaced Super I/O again, this time using one from a donor board (same model & revision). Perfect solder job, aligned, inspected under microscope → No change.
    Power Rails & Signals
    • +3VALW is missing
      → Should be enabled by the Super I/O, but the EN signal is not generated.
    • Replaced PCH (Platform Controller Hub) and reprogrammed BIOS chip with a clean firmware → Still no change.
    • Verified:
      • 19V input present
      • +3VLP present (feeding Super I/O)
      • +5VALW present
      • PU301 replaced (no change)
      • +1.05VALW impedance OK
      • No shorts on CPU/GPU VRMs, audio, or network ICs
      • All components appear intact visually – no burns, no missing parts
      • Board is clean, no soldering accidents
    • Tested by injecting voltage manually into +3VALW rail (with previous PCH)
      → PCH slightly warmed up
      → No abnormal consumption or heating elsewhere
    Current Status
    • Board does not power on
    • All major voltages present except for +3VALW, which depends on an EN signal from the Super I/O
    • Super I/O receives power and ON/OFF signal but does not release EN to trigger power sequencing
    • I've exhausted the typical troubleshooting steps and now I'm stuck.
    Request for Help


    I strongly suspect the issue lies in the Super I/O logic or some missing condition it needs to allow the EN signal to be generated.

    If anyone has experience with this board or similar behavior, what conditions must be met for the Super I/O to enable the +3VALW rail?

    If you need voltage references or specific measurements, let me know—I'll provide whatever is needed.

    Thanks in advance!
    Tags: None
    #2
    Additional Info


    Just to complement the information:
    • No signs of low impedance, shorts, or high consumption around JPQ1, JPQ2, or after UQ2.
    • I also tested by injecting 3.3V via PJ302 (with 19V present and the board switching 5V by itself).
      → The board draws 0.184A (184mA) in this condition.

    Regarding the initial short on the Super I/O (which was the first component replaced):
    • The short was located on the +3VLP line.
    • After replacing the Super I/O, the impedance returned to normal, the short was gone, and the +3VLP rail came back as expected, as mentioned earlier.

    Comment

      #3
      +3VALW will come up only after triggering the mb as per power sequence but EC_ON should be present in off condition(seems contradictory to me).

      Have you checked RTC circuit? Main bios flashed?
      Have you checked resistance to GND on switched rails like +3VS/5VS etc.(Pg 78)?

      Comment

        #4
        Originally posted by mcplslg123 View Post
        +3VALW will come up only after triggering the mb as per power sequence but EC_ON should be present in off condition(seems contradictory to me).

        Have you checked RTC circuit? Main bios flashed?
        Have you checked resistance to GND on switched rails like +3VS/5VS etc.(Pg 78)?


        My response:

        Thank you for your comments. I think you may have misunderstood some parts of my explanation, so let me clarify:
        1. +3VALW Sequence
          You're correct that +3VALW only appears once the board is triggered—so I did read the start‑up sequence properly.
        2. EC_ON
          EC_ON is present even when the board is off. I confirmed this because I'm seeing +5VALWP generated by PU502, which receives 5V_EN via EC_ON directly from the SIO.
        3. Main BIOS (UT5)
          Asking whether the main BIOS is “working” doesn't make sense in this context: if the board never reaches the start‑up sequence, you won't even see +3VALW at the EEPROM pin—so it can't possibly be operating.
        4. Switched Rails (+3VS/ +5VS)
          I checked for low‑impedance shorts or unexpected current draw around JPQ1, JPQ2 and downstream of UQ2 and found none. Here are the measured resistances to ground after UQ1:
          • +5VS (after JPQ2): 3.78 kΩ
          • +3VS (after JPQ1): Rising infinitely on high‑ohm range until it eventually zeroes
        5. RTC Circuit
          Everything looks fine here:
          • DH1: 3.21 V at pin 3 (+CHGRTC)
          • +VL_RTC (pin 1): 3.00 V
          • RTC battery pin (pin 2): 0 V with the coin cell removed; restores to ~3 V when installed
          • I also verified +3VL_RTC at the PCH side—across CH47/CH48 and RH99/RH98/RH51.

        Any other ideas on what I can test next?

        Comment

          #5
          Just to clarify, the correct motherboard model is LA‑L181P, not LA‑J871P.

          Comment

          Previous template Next
          Working...
          X