LA-9865P boot/power looping
Background:
Laptop came in as not powering ON (and seemed to have been worked on previously). It also had printer toner spilled all over it. Once opened, I saw that some printer toner made its way near ram slots, ODD and SOC.
After removing the heatsink, it does not seem that toner got to the SOC (it was mostly on the heatsink). I cleaned it as much as possible using compressed air and a fine brush. Also avoided using any liquid to avoid clumping of the toner powder.
After initial diagnostics, I found a defective mosfet (PQ205) and replaced it. I now have standby light but when I tried turning on, I get the first power cycle (ON-Off-On) but then it keeps cycling every 5 seconds or so for about 5 to 7 cycles and stays off (with no image). The same thing starts over again when power button is pressed.
All voltage rails are present and stable while its ON. In off state I have stable 3.3 and 5V alwaysON voltage. CPU VCore is 1.75V and VGPU is 0.90V and stable.
All power good/OK signals are present while all rails are on and stable.
However, PLT_RST# is present only briefly (please see attached picture) and DIMM_DRAMRST# does not go above 0.72V (Neither PLT_RST# nor DIMM_DRAMRST# is shorted to ground).
I checked R184 and it is fine. I have 1.35V on one side and 0.75V on DIMM_DRAMRST# side (It can be seen changing from 0V to 0.75V when power button is pressed though). VTT voltage is OK (0.68V)
I also don't have any activity on PM_SMBDATA & PM_SMBCLK (they are constant at 3.3V). No activity on BIOS (Constant 3.3V).
What I tried so far:
1. Reprogram BIOS - Same issue
2. Replaced EC - Same issue
3. Tried known good RAM - Same issue
4. Clean RAM slot with a bath of alcohol and medium hardness brush (I don't have ultrasonic (yet)) - Same issue
5. Replaced just in case but no change.
6. Tried with and without battery (battery charges fine by the way) - Same issue
7. No shorts were found
Motherboard: VSKTA LA-9865P Rev1A
Do I have a bad/dead SOC? Please find attached schematic. MOD Edit: Schematic removed.
Laptop came in as not powering ON (and seemed to have been worked on previously). It also had printer toner spilled all over it. Once opened, I saw that some printer toner made its way near ram slots, ODD and SOC.
After removing the heatsink, it does not seem that toner got to the SOC (it was mostly on the heatsink). I cleaned it as much as possible using compressed air and a fine brush. Also avoided using any liquid to avoid clumping of the toner powder.
After initial diagnostics, I found a defective mosfet (PQ205) and replaced it. I now have standby light but when I tried turning on, I get the first power cycle (ON-Off-On) but then it keeps cycling every 5 seconds or so for about 5 to 7 cycles and stays off (with no image). The same thing starts over again when power button is pressed.
All voltage rails are present and stable while its ON. In off state I have stable 3.3 and 5V alwaysON voltage. CPU VCore is 1.75V and VGPU is 0.90V and stable.
All power good/OK signals are present while all rails are on and stable.
However, PLT_RST# is present only briefly (please see attached picture) and DIMM_DRAMRST# does not go above 0.72V (Neither PLT_RST# nor DIMM_DRAMRST# is shorted to ground).
I checked R184 and it is fine. I have 1.35V on one side and 0.75V on DIMM_DRAMRST# side (It can be seen changing from 0V to 0.75V when power button is pressed though). VTT voltage is OK (0.68V)
I also don't have any activity on PM_SMBDATA & PM_SMBCLK (they are constant at 3.3V). No activity on BIOS (Constant 3.3V).
What I tried so far:
1. Reprogram BIOS - Same issue
2. Replaced EC - Same issue
3. Tried known good RAM - Same issue
4. Clean RAM slot with a bath of alcohol and medium hardness brush (I don't have ultrasonic (yet)) - Same issue
5. Replaced just in case but no change.
6. Tried with and without battery (battery charges fine by the way) - Same issue
7. No shorts were found
Motherboard: VSKTA LA-9865P Rev1A
Do I have a bad/dead SOC? Please find attached schematic. MOD Edit: Schematic removed.
Attached Files
Comment