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Another 820-3115 that's killing me, no pp3v3_s5.

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SMMRepair

Member
Working on this 820-3115 board that had some "rough" handling by someone prior to me getting it. Replaced ~10 components that were broken-off/missing (mostly non-critical caps/resistors, etc). Confirmed all parts are now present on the board, but I can't restore power, with the following symptoms:

1. Board has ppbus_g3h, pp3v42_g3h, ppvrtc_g3h, pp5v_s5 all present and stable/normal, but pp3v3_s5 is 0v.
2. Pin 6 of U7200 is .8v, which I believe is normal, but pin 23 is 0v.
3. PP5v_s5 is present and stable, despite pin 23 of U7200 not being present (this confuses me).
4. SMC_PM_G2_EN is present and stable (3.45v)
5. Charger light is solid green the entire time, but it flickers ever so slightly, as if it's trying to power on. All SMC power lines stable/normal.
6. No shorts on pp3v3_s5, ppbus_g3h, pp3v42_g3h or pp5v_s5
7. Replaced U7200 (twice--three total chips), U7941 and Q7221, no change

I'm not sure where to go from here. All help appreciated--thanks!
 
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SMMRepair

Member
Thanks for the reply! I guess I was confused on the order of the signals; that makes sense that pgood wouldn't show up until both 3v3 and 5v were active. I believe I thought that the PGOOD signal came before 5v and 3v3 were sent out, but that doesn't make sense.

RTG at L7220 is 15.42 kOhms. At L7260 it's 31 kOhms.
 
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dukefawks

Administrator
If there is 0.8V on pin 6 the U7200 is being told to turn on. If PPBUS is present at Q7220 there should be 3v3_s5. If not the problem is in the U7200 circuit, check all voltages, resistors and caps.
 
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SMMRepair

Member
Thanks, Duke. Pin 6 of Q7220 is 0v. I get PPVIN_S5_3V3S5 (PPBUS_S5_HS_OTHER_ISNS) on pin 1 of C7241, so Q7220 is getting power. I won't lie, I've never been very comfortable with how MOSFETs work (I've read so much information on P-type vs N-type, but I don't understand which voltages come and go in some of the Apple schematics; they always seem to look different than the sample diagrams online...more complex; I get gate/source/drain, but the Apple schematics always look so much more complex), but since P3V3S5_DRVL and P3V3S5_DRVH are both gate signals (and output low/high MOSFET driver signals from U7200), does this mean U7200 is still at fault? At U7200, pins 10 and 12 are both 0v.
 
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dukefawks

Administrator
There is nothing to measure at the output FETs just switching signals so multimeter won't make much sense.
U7200 is being told to turn on by the 0.8V on pin 6 but there is no output. If there is no short on 3V3_S5 then the issue is around U7200, not much more I can say about it. Check if LDO outputs of U7200 are all working too (vref/vreg).
 
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