820-00165-A ppbus_g3h low.

Yoel Ren

Member
hi, this came in with ppbus 8.2v
i changed smc straight away, ppbus go 8.6v, machine turn on.
a few days later,customer came, the machine is dead again.
I see ppbus_g3h is 4v,sometimes 0.5v.
I remove fuse, and I have 8.6v at pin 1. so it must be system side ? do i check for short one by one?
I have seek thermal cam, but nothing shows heat.
 

2informaticos

Administrator
Staff member
Resolder the fuse and check diode mode reading on PPBUS_G3H.
Compare reading with all big coils.

Check resistance between pins 17/18 and 27/28 of U7100.
Did you try SMC bypass?
 

Yoel Ren

Member
diode mode with fuse connected : 0.110
resistance 17/18 27/28 3.5 and 20 ohm, normal.
the closest value i found is at :
L7130 : 0.115
L7630 : 0.120

the rest diode mode is around 0.300 - 0.400, looks good.
L7310 and L7320 is 0.05, i think its normal.
cant start in smc bypass.
 

Yoel Ren

Member
with fake charger, still the same exact behaviour.
when i leave the board long enough, the ppbus will start at around 8v, and then slowly dropping to very low value. (2v or something )
 

2informaticos

Administrator
Staff member
Change U7100 and check all its solders, traces and surrounding components.
Board turns on with a charged battery?
 

Yoel Ren

Member
u7100 changed, all component surrounding has been checked, all good.
board doesnt turn on with charged battery.
ppbus_g3h start at 8.6v when i plug magsafe, and drop slowly till magsafe light goes off.
 

2informaticos

Administrator
Staff member
Post U7100 basic voltages; pins 1, 2, 3, 9, 12, 13, 14, 17, 19, 20, 27.
Specify which ones drop in time.
3V42_G3H stable?
 

Yoel Ren

Member
1 0v
2 16v stable
3 4.3v stable
9 0v
12
13
14
17
19
20
27
midway writing this, found out pp3v42 is only around 1.8v
pp3v42 diode mode is 0.278, good.
 

Yoel Ren

Member
i have ppvin_p3v42g3h, u7090 looks touched before by previous technician, so I replaced and I have stable pp3v42 and its turning on now, will get back later if something is wrong again.
 
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