MacBook Air a1370 only runs on the charger

[crea2k]

Iv got a feeling this could be the customers crappy battery causing half of this. I know the dc in board looked like garbage as it was water damaged and had components missing. So that was replaced and the voltage appears to be getting through ok now. Iv ruled the isl chip out as changed that. Iv just checked the customers battery and it's zero volts at the terminals. If I measure the cell tabs it's 1.9v so it looks like the bms under voltage protection has kicked in. I tried charging it by dtps and it wasn't having any of it, which explains why it was saying to replace the battery as the bms was probably telling the motherboard the battery was below minimum cell voltage (usually 3 volts on a lithium battery).
So have ordered another in, so will see how that goes.

[crea2k]

Here are some voltages from around ISL6250 :

PP3V42_G3H
3.39v

CHGR_CSI_P
14.50v

CHGR_CSI_N
14.45v

CHGR_BOOT
12.89v

CHGR_UGATE
10.95

PP5V1_CHGR_VDDP
5.05v

CHGR_CSO_N
8.36v

CHGR_CSO_P
8.36v

SMC_BC_ACOK
2.97v

CHGR_RST_L
3.3v

CHGR_VNEG_R
1.3v

CHGR_VCOMP_R
1.3v

CHGR_DCIN
14.2v

CHGR_ACIN
3.74v

CHGR_ICOMP
1.54v

CHGR_CELL
0v

CHGR_VCOMP
1.52v

CHGR_VCOMP_R
1.44v

tested :
R5420 = good
R7085 = 0.469M
R7080 = good
R7081 = good
R7005 = good

Voltage @ R7005 = 14.1v & 14.35v
Voltage @ R7080 = 14.69v & 5.57v
Voltage @ R7001 = 5.1v & 5.05v
Voltage @ R7085 = 14.62v & 5.7v
Voltage @ R5420 = 0.061v & 0.061v

[crea2k]

So im testing PPDCIN_S5_CHGR on Q7080 and am getting 14.5 volts but it should be 18.5v according to the schematic. If I measure resistance to ground on that line I get 040.0kohm , but without another board to compare to that is meaningless, all we know what is happening so far is the voltage isnt what it should be on that line, so il see if I can find any filters or something on that line. Iv tried two charger and two dc in boards and get that same 14.5-14.8volts at the dc in board connector.

[crea2k]

Right using google images im guessing its a
MacBook Air 11" (Mid 2011) 820-3024

[crea2k]

[crea2k]

Well I changed the ISL6259, but still the same problem, im trying to find some kind of schematic for it, but with macs it seems to be about 1000X harder to actually identify what you actually have in front of you as they call them all the same thing.

[crea2k]

Ah cool ok thanks, il see if I can find out which ic this is. Reading the schematics is simple enough it's that stupid board view software that drives me round the bend. Why the layout can't just be on the same PDF I don't know.

[Jessa_the_Professa]

On the MacBook Pro, there is a tristar-like chip that senses the dc in charger, produces the 'ac ok' signal that allows the charger voltage to enter the device, communicates with the smc to initiate charging, and then generate the main power voltage to turn the whole machine on, monitor the dc and battery voltages and actually do the action of charging. This system is on a couple of pages of schematics and is the most common failure point for macbooks for both water damage and electrical damage. Louis probably has 20-30 videos on a wide variety of faults within this system--which are largely "the charging chip is bad" "dudes or traces surrounding the charging chip are bad" or "the SMC itself is bad" He walks through this circuit in any video with the work 'charging' or 'sys onewire' and that is a great resource if you haven't worked on macbooks but have a good general understanding of schematics. I believe the MacBook Air will be different from the standard macBook Pro charging system, but likely very similar.

The DC in board you changed is just that---a plug to convey DC input to the board.

[crea2k]

It's definitely the logic board as the customer tried 2 different batteries, Iv tried two different chargers and dc in boards. We just don't know what on the motherboard is bad as other than the backlight circuit I know Jack when it comes to fixing macs.

[crea2k]

Is the charging chip on the dc in board or is that seperate ?, iv changed the dc in board itself.

[Jessa_the_Professa]

What does the charging chip area look like? Was there water there? I haven’t fixed any air charging problems, but for MacBook Pro it is just a couple of pages of schematics. When I troubleshoot MacBook Pro charging, I check for output of the charging chip—smc_bc_acok and if that isn’t present troubleshoot why. The charging chip area has some battery current sensing resistors and I would expect that Louis has videos dedicated to this exact problem with a method to differentiate charging chip problems from battery data line problems from SMC failures.

[eDigitCom]

an know good logic board if you could get one would really narrow the fault done. not much more to try i think

[crea2k]

Yes the mag safe was replaced, the smc resets when the battery is removed.

[eDigitCom]

You could be done to the logic board itself??

[eDigitCom]

Was the Mag-Safe control board replaced

Was the SMC Reset (system management Controller)??