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820-00165 PP3V3_S0 Low

C

CRC2018

Member
so i've got an 820-00165 in which had no power - I located a short on PPBUS_G3H and blown F7140. Located the short down to a shorted out cap and replaced, also replaced F7140 after confirming there was no further short.
Board powers up enters S0 state has fan spin but CPU VCORE is missing also ALL_SYS_PWR_GOOD is missing. Checked PP3V3_S0 and i'm only getting 0.65V there instead of 3.3v. PP3V3_S3, PP3V3_S4 and PP3V3_S5 are all 3.3v as expected. No short on PP3V3_S0 - it's reading 2.5kohm to ground.

I've replaced U1950 just to rule that out but no difference


No liquid board is very clean i'm a bit stumped as to where to go with this one - clearly the low voltage on PP3V3_S0 will prevent VCore from being turned on but I cannot see anything visible on the board which would cause this issue. - the resistance on L7410/L7420 to ground is 30ohms so looks like the CPU is ok.
 
C

CRC2018

Member
Thanks once again - nailed the issue in one. Checked U8030 had 3.3V on the input side ok, looked then carefully at U8030 under the scope and saw a tiny crack on one edge of it. Pulled a replacement from a scrap 820-3437 and system works perfectly now, starts up, chimes boots only other issue is the battery wouldn't charge or run off the battery even though it was showing 70% charge. Tried a known good battery which works fine so I don't know what is going on there. Best guess i've got is the macbook was dropped - the original cap with the short was cracked as was U8030 so maybe something broken inside the battery.

One interesting observation i've made on this 820-00165 - U8030 was not covered with hot glue like it is on 820-3437 - therefore easily liable to damage! I'm not sure if that is supposed to be that way and i'll make a note to check the next time an 820-00165 comes in if this IC is covered or not.
 
C

CRC2018

Member
Yes it works perfectly with the known good battery, charges, runs off it, reads the battery % and cycles no issue there. Quoted customer for a replacement battery and fitted it machine is done now. I may in future open up the old battery and see if I can find anything wrong with it!
 
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