820-2879 PPBUS 1V

No-Clean

Member
Initially PPBUS was ~1V, I then replaced U7000 and Q7035 I now get ~4V on PPBUS then it starts to drop down close to 0V, loops then next time around starts around 11V then rapidly drops down to 0V and repeats the loop.

Checked pins 17-18 and 27-28 of U7000 and those are fine
3V42 resistance is around 240K after replacing U7000, before that it was like 11k

I've never seen this before, please help.
 

2informaticos

Administrator
Staff member
3V42_G3H steady value?
Did you try SMC bypass mode?
Replace C7025, just in case; maybe Q7030 too.
Check diode mode to ground at L7220; any voltage pulse there?
 

No-Clean

Member
3V42_G3H steady
Replace C7025 same thing
Replace Q7030 same thing
Diode read on L7220 is 0.130 on both ends
Pulse every 7-8 seconds on L7220 ~3V
 

2informaticos

Administrator
Staff member
Post U7000 voltages; pins 1, 2, 3, 6, 9, 12, 13, 14, 15, 17, 19, 20, 27.
Check the R/C networks from pins 5, 7, 8.
Be sure R7012 is good.
 

No-Clean

Member
ISL
1-16v BUT PULSING
2-16.5V
3-4V
9-0.031V
12-3.4V
13-3.4V
14-3V
15-0
17-PULSING 11V then it starts to come down to ~3V
19-5V
20-5V
27-PULSING 16V then it starts to come down to ~6V

17/18- 5 ohms
27/28-22 ohms

R7012 1k Good

Check the R/C networks from pins 5, 7, 8 please explain what to do.
 

2informaticos

Administrator
Staff member
You said to have 4V at PPBUS_G3H.
If in fact, if fluctuates 3-11V, then SMC can cycle power, because detects something wrong.
Check what happens in SMC bypass mode.

If R7020 voltage fluctuates, you may need to change Q7080/85.
PPDCIN_G3H also fluctuates?
If yes, test with fake charger, or lab PSU and 60/85W Magsafe 1 cable.
 
Last edited:

No-Clean

Member
Yes PPBUS fluctuates down from ~12V to ~4V then cycles
SMC bypass I get not light on charger and 3.3V steady on PPBUS
R7020 does fluctuate
PPDCIN_G3H steady ~16V
Replaced Q7080/85 same thing
 

No-Clean

Member
With F7040 removed C7040 voltage starts around 3.4V then drops down from there and loops around.
Diode mode reading on L7220 is 0.140 and on L7260 is 0.425 both measured with F7040 removed.
 
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