OPTI-495SLC 386 WB mainboard fails to POST but not after reset

Collapse
X
Collapse
 
  • Page of 1
  • Time
  • Show
Clear All
new posts
Previous template Next
  • Sorrow1
    New Member
    • Mar 2023
    • 4
    • CZ
    #1

    OPTI-495SLC 386 WB mainboard fails to POST but not after reset

    Hi,

    I'm repairing OPTI-495SLC 386 WB manboard: https://stason.org/TULARC/pc/motherb...LC-386-WB.html

    It has some damage due to battery leak that I have cleared. I measured affected wire patches and they seems to be OK. The damaged part is shown on the attached picture.

    The board often fails to POST when I turn the PSU on. Most often POST card gives AMI BIOS 12/13 error codes but no code or different codes are also shown sometimes.

    When I reset the board while the PSU is running or if I switch it OFF/ON the board BOOT normally (in 100% of reset restarts).

    I measured the PSU with multimeter and I also tried another PSU to exclude any issue there.

    My guess is that some component on the board needs time (after power on) to start functioning properly but I lack experience to identify it

    Any ideas what to do and where to start?

    Jan
    Attached Files
    Tags: None
    Previous template Next

    Related Topics

    Collapse
    • ictc
      Philips MDP 3380/12 Blu-ray Player – No Power, Reset Signal Always High
      by ictc
      I'm troubleshooting a Philips MDP 3380/12 Blu-ray player that shows no signs of life. The display remains off, and no buttons respond.

      Inside, the power supply is working correctly, and all expected voltages on the mainboard match the service manual specifications. The CPU warms up slightly (checked with a thermal camera), the crystal oscillator is functioning, but the reset signal remains high at all times.

      The reset circuit appears to consist of two NPN transistors, one driven by 5V VCC and the other by 3.3V STBY, as shown in the attached schematic. Should the reset...
      02-25-2025, 12:15 PM
    • orcic
      MASTER TL240 and new mainboard LW36BKC01
      by orcic
      Hello,
      I have an old MASTER TL-240 LED TV. Since it stopped working and it had a DVB-T receiver that is being dismissed in Italy, I've decided to replace the mainboard with a DVB-T2 one.
      The original problem was that when switching on the TV, the power LED was transitioning from red to steady blue, without showing video or audio.
      After checking some voltages on the power supply board (HKL-240101-B Rev. 1.4, HKL from now on) someone suggested me to replace the mainboard.
      Now I have some doubts about how to connect the new mainboard to the old power supply.
      First of...
      05-12-2023, 08:10 AM
    • Devonavar
      Vizio M43-C1 - How closely do I need to match the mainboard number?
      by Devonavar
      I have a Vizio M43-C1 stuck in a reboot loop with no backlight.

      I've tested all the voltage rails coming out of the power supply and they are "normal" for this model (PS_ON & DIM go high when turned on, BL_ON & 3D_ON are close to zero due to backlight power flowing through the mainboard, 5VSB is 5V, and 12V is 19V, which is apparently normal for this board).

      Basically, I get similar results to Garry in this post: https://www.badcaps.net/forum/showthread.php?t=80346

      So, I've ruled out the PSU for now.

      The reboot loop...
      08-14-2022, 08:46 PM
    • Malva
      Problem LG 49UB850V (Mainboard: EAX65684604 / EBT62954607)
      by Malva
      Hi everyone,
      I'm trying to repair my LG 49UB850V TV (WebOS 1.0, UHD model from 2014).
      Mainboard model: EAX65684604
      PCB marking: EBT62954607
      SPI chip: Winbond W25X20CLNIG Problem description:


      Originally, the TV would turn on (backlight and LED OK if I force them on), but it shut down as soon as any input was received from the IR sensor or remote. The backlight and power board were working fine.

      After testing and verifying the voltages (DRY ON, PWR ON, 12V/24V rails), I suspected a corrupted SPI firmware. What I tried so far:
      • I bought another
      ...
      06-25-2025, 02:07 PM
    • l0lhaxz1
      QN65QN90A - Mainboard MLCC failed - now bootloop
      by l0lhaxz1
      Hi

      I have a QN65QN90A which was purchased around launch I guess making it about 1.5-2 years old... had been working fine until a few days ago, simply went black and would no longer turn on (at all). No standby light and no typical PSU relay click etc. Absolutely dead.

      Pulled it apart without doing much research first, suspecting the power supply as it had a faint buzz (I guess due to the forthcoming found short), investigated PSU for some time and concluded there was no fault that I could spot with the board removed.

      Came to learn after a bit more research...
      02-06-2023, 08:59 AM
    • Loading...
    • No more items.
    Working...