820-2641 No Boot LED 1 Blinks

donnos

Member
Board does not boot and LED 1 only blink.

pp12V_G3h - 12V
pp12V_s5 = 12v
pp3v42 - 3.41
pp5v_s5 = 4.9
pp3v3_s5 = 0
PM_EN_P3V3_S5_REG = 3.8v constant.

Tried replacing u7700 - same, but i replaced with ISL62383C same outcome.

i removed R7776 to cut pp3v3_s5 from load, i get still get 3.3 for split second.
 

2informaticos

Administrator
Staff member
Post basic voltages for U7700; pins 17, 18, 4, 5, 12.
Change it with normal ISL62383, not with "C" suffix.
 

2informaticos

Administrator
Staff member
3V3_S5 should appear.
If not, check all related resistors and traces; pay atention to R7710 and C7714.
Also check diode mode to ground at L7710.
Be sure to use correct ISL62383 version.
 

donnos

Member
have double checked and triple checked, replaced another ISL62383 for good measure and still get the same results.
removed all resisters connected to the ISL and measured them individually,

this should be a closed circuit. this is gonna keep me awake for days trying to solve
 

donnos

Member
Yes i have checked on p5vs3 lines as well and they are all within spec. i have injected 3.3v to pp3v3_s5 as well as 5v to pp5v_3 and both don't show shorts and have current draw less than 100ma
the only thing have not looked at is Q7110. measurements all looks good, gonna order some parts and try to replace then
 
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