Hi guys,
Been trying to fix up this one for a while, but still a beginner on diagnosing. Hope you can bear with me on a potentially long-winded explanation, will to keep it brief.
Got this one as a fixer-upper, arrived with screen hinge busted, missing riser posts for cpu and gpu, and no lights on attaching ac adapter.
tried inspection, short detection but seemed like issue was in boot.
Measured and got these readings
+3VA = 3.3
+5VA = 5.00
PS_ON = 3.3
+3VA_EC = 3.3
EC_RST# = 3.23
3VDSW_ON = 3.3
+3VA_DSW = 3.3
3VA_DSW_PWRGD = 3.3
PWR_SW# = 3.3
DPWROK_EC = 0.28
PM_RSMRST = 0
got myself a CH341A and flashed clean bios, removing and replacing BIOS chip but no go, no difference.
then I followed a red herring noticing that +3VS (input line feeding the EC) = 0, and traced the source to originate from +12VS, that coming from an NPN/PNP SMD PUMD12. Thought that was broken but now in hindsight it might not have been, I think this power rail isn't meant to get activated until PCH sends SUSB/SUSC_EC signals?
The odd thing is in another phase of random fault finding I was dousing this part of the board where the 12V rail was with IPA, and once in a while the fans would kick in. I don't know if it was causing some kind of short that would do this. hasn't done this now for a while, so i hope i didn't break something else.
Anyway, I replaced the two SMDs generating 12V/12VS, and replaced the riser posts at the same time. plugged it in and a standby light appeared! I thought my diagnosis of the 12V/12VS had been right. but still no boot. no charging light or any sign of actual charging.
but holding keyboard power button for 10 secs does turn the standby light off so the keyboard/PWR_SW mechanism seems to work. So my sense is if the standby power light is on.. that means the EC is getting power and doing something as it is what generates that signal... not completely broken. But it's not generating a PM_RSMRST so PCH never kicks in boot. but standby 3V/5V voltages are present. Any advice on other things to check for that would lead to missing PM_RSMRST?
My best guess now is the EC chip IT8995 might be corrupted, either needs reflashing or should be replaced. The weird standby light showing up after working on unrelated items makes me wonder if there was a slight reflow that happened from my soldering other parts nearby.
However the EC is a tiny BGA chip (VFBGA-128), and I've never done a BGA reinstall before. Cost wise though it is tempting to try to replace rather than reprogram. aliexpress $10 chip preprogrammed, vs RT809F+PEB-1 $90. Any advice here as well? most of the EC replacement videos I've found are dealing with the bigger form factor.
Thank you!
Been trying to fix up this one for a while, but still a beginner on diagnosing. Hope you can bear with me on a potentially long-winded explanation, will to keep it brief.
Got this one as a fixer-upper, arrived with screen hinge busted, missing riser posts for cpu and gpu, and no lights on attaching ac adapter.
tried inspection, short detection but seemed like issue was in boot.
Measured and got these readings
+3VA = 3.3
+5VA = 5.00
PS_ON = 3.3
+3VA_EC = 3.3
EC_RST# = 3.23
3VDSW_ON = 3.3
+3VA_DSW = 3.3
3VA_DSW_PWRGD = 3.3
PWR_SW# = 3.3
DPWROK_EC = 0.28
PM_RSMRST = 0
got myself a CH341A and flashed clean bios, removing and replacing BIOS chip but no go, no difference.
then I followed a red herring noticing that +3VS (input line feeding the EC) = 0, and traced the source to originate from +12VS, that coming from an NPN/PNP SMD PUMD12. Thought that was broken but now in hindsight it might not have been, I think this power rail isn't meant to get activated until PCH sends SUSB/SUSC_EC signals?
The odd thing is in another phase of random fault finding I was dousing this part of the board where the 12V rail was with IPA, and once in a while the fans would kick in. I don't know if it was causing some kind of short that would do this. hasn't done this now for a while, so i hope i didn't break something else.
Anyway, I replaced the two SMDs generating 12V/12VS, and replaced the riser posts at the same time. plugged it in and a standby light appeared! I thought my diagnosis of the 12V/12VS had been right. but still no boot. no charging light or any sign of actual charging.
but holding keyboard power button for 10 secs does turn the standby light off so the keyboard/PWR_SW mechanism seems to work. So my sense is if the standby power light is on.. that means the EC is getting power and doing something as it is what generates that signal... not completely broken. But it's not generating a PM_RSMRST so PCH never kicks in boot. but standby 3V/5V voltages are present. Any advice on other things to check for that would lead to missing PM_RSMRST?
My best guess now is the EC chip IT8995 might be corrupted, either needs reflashing or should be replaced. The weird standby light showing up after working on unrelated items makes me wonder if there was a slight reflow that happened from my soldering other parts nearby.
However the EC is a tiny BGA chip (VFBGA-128), and I've never done a BGA reinstall before. Cost wise though it is tempting to try to replace rather than reprogram. aliexpress $10 chip preprogrammed, vs RT809F+PEB-1 $90. Any advice here as well? most of the EC replacement videos I've found are dealing with the bigger form factor.
Thank you!