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820-3435 not turning on missing PP5V_S4RS3

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laptopcity

Member
820-3435 not turning on missing PP5V_S4RS3 which if im right turns on u8080 to make pp5v_so, question is i cant find where PP5V_S4RS3 comes from,originally the board was liquid damaged, replaced u7090 c7090 c7091 r7005 r7006 due to short and missing pp3v42g3h and no green light (now working) , replaced u7501 due to missing pp5v_s5 (now working) so if im right just need to find missing pp5v_so
 
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JohnB8812

New member
PP5v_S4RS3 comes from PM_SLP_S4_L which sucks. Check usual spots for corrosion U1900, U1950, SPI termination resistors and traces to the BIOS. Also make sure PP3v3_S5 is present and PP3v3_SUS is present at the BIOS and in general. So many things can cause missing S4 rails.
 
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dukefawks

Administrator
Yeah, check corrosion on U1900/50 pull them and inspect. Also check PPVRTC. Check for power cycling on 5V_S4 preferably with scope as multimeter it is difficult to catch the very short pulses.
 
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laptopcity

Member
changed u1900 / 1950 just incase PPVRTC IS 3.3V , BUT PP3v3_SUS is missing from the board , when i look to see where it is created from it looks like it comes from the cpu is that correct ?
 
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JohnB8812

New member
PP3v3_SUS is created by U8020. Check if PP3v3_S5 is making it's way into it and check if P3v3SUS_EN is present.
 
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laptopcity

Member
think im learning :) , yes traced back to u8020 PP3v3_S5 is there but P3V3SUS_EN isnt there , which when i try to find where it comes from i end up at the cpu :-(
 
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dukefawks

Administrator
P3v3SUS_EN should certainly have a diode mode reading with red probe on GND. Check again and compare to a another board. Bad trace?
 
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