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820-3662: Short on U1100 Pin 41

M

macRepairAmb

Member
So I've isolated the short on PPVRTC_G3H to U1100 Pin 4 (Pulled C1532, 1533, 1531, 1910 and U1900 to confirm none of those were causing the short).

Apart from making sure that I pull U1100 from an identical board (820-3662), is there anything else I need to do before and after swapping the chip?
 
2informaticos

2informaticos

Administrator
Staff member
Buy new PCH.
Is not expensive and easy to find real new.
After changed it, you need to clean ME region in BIOS.
 
M

macRepairAmb

Member
Oh wow. Thanks. Thought I had to pull one from an identical board. Awesome will just buy one and save me the trouble and time. Thanks.
 
M

macRepairAmb

Member
Replaced U1100, refreshed EFI will clean ME. Boot powers up with fan spin but never boots. The cpu is cold. I noticed the CPU gets warm when I the medusa connected for the flashing of the chip. What signals from U1100 would suggest I check to confirm this is work as it should?
 
2informaticos

2informaticos

Administrator
Staff member
Try full known good BIOS.
Main BIOS could be corrupted; in such case cleaning original ME doesn't help.
 
M

macRepairAmb

Member
Used a known good BIOS with the same result. Decided to check around the chip, and found pin 427 PM_SLP_S4_L @ 1.8 instead of 3.3. Resistance reading is 8k on defective chip and 19k to ground. The resistance of the resistor was also 8k on the bad board and 100k on a good board.

Ordered replacement chip.
 
M

macRepairAmb

Member
Replaced U1100 again, now the board won't power up. Missing PP5V_S4.

S4_PWR_EN - 0
PM_SLP_S5_L - 0
SMC_S4_WAKESRC_EN - 0

Is it possible PM_SLP_S5_L from U1100 could be the issue?
 
2informaticos

2informaticos

Administrator
Staff member
Do you get 3V3_S5/SUS?
Check if PM_PWRBTN_L reacts (drop pulse) when trigger SMC_ONOFF_L.
PM_RSMRST_L should be always high, of course.
 
M

macRepairAmb

Member
So after reheating the U1100 chip to make sure all solders connections were made, now S4_PWR_EN cycles from 0.082 to 3.3. Even PP5V_S0 cycles too.
 
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