Apple A1425 retina does not power on after BAT depletion

[marce002]

Hello

I have received this mac from another collegue, he says powers on ok, runs fine, runs fine on battery only, and also charges fine, but if you let the battery dry for several days, then it wont power on, and no charging and no led on charger cable... he claims to short "f7040 and R7020" for half a second, and the mac turns on and starts charging again..
what to start looking at?

note: he was also referring to have repaired the 3.4v power section, and touching the area.

thankls in advance

[reformatt]

Re: Apple A1425 retina does not power on after BAT depletion

Voltage at R7012 and D7005 pin 1 and 3 during no power state? Genuine or non-genuine charger being used?

[marce002]

Re: Apple A1425 retina does not power on after BAT depletion

no power zombi mode:

19.13V at R7020
0.56V at F7040

genuine MAC charger, in fact when is ok led green and amber is normal, charging ok.


thanks in advance, really.

[mon2]

Re: Apple A1425 retina does not power on after BAT depletion

Resistance to ground on PPBUS_G3H? Remove all power when measuring resistance.

[marce002]

Re: Apple A1425 retina does not power on after BAT depletion

it is 0.923Kohm, battery and charger not connected, red probe on ground.

diode mode same location pins is:0.152V

[mon2]

Re: Apple A1425 retina does not power on after BAT depletion

You have a short on this line.

Remove the fuse F7040 and then power up again.

Measure the voltage to ground on each pad of the removed fuse on the PCB.

Do you now see a correct PPBUS_G3H voltage on the ISL side ?

[reformatt]

Re: Apple A1425 retina does not power on after BAT depletion

Dual diode D7005 takes power either from the adaptor or via PPBUS_G3H (which would be available if battery is charged, absent if it isn't). You didn't give me a reading for that. Without voltage here you won't get any PP3V42_G3H. Seen the legs on this didoe corroded from liquid damage.

[marce002]

Re: Apple A1425 retina does not power on after BAT depletion

MON2
and
REFORMATT:

They explained me that the 3.42V generation was "area destoyed, and no replacing parts", and they put an "external" small circuit to generate those 3.42v with an external IC out of the mother behind the cooler. The problem i See is that they connected this external 3.42v generation to F7040 directly, so they can have 3.42v and the laptop works fine... but... to generate 3.42V, (i think) they need "battery power" because power source for that external 3.42 is connected to F7040... right? so no ac charger in there...
I think when battery is depleted for storing a long term, the mac cant turn on, this is my deduction tell me if Im wrong... where would you connect instead?

PD reformatt still not detached the motherboard to test pin 3 in diode

thnks both

[mon2]

Re: Apple A1425 retina does not power on after BAT depletion

Correct. To create this low current power rail of 3v42, you need the dual anode diode. Then it should feed into this 3v42 regulator.

One leg to F7040; other leg to the battery feed. Just like the original schematic. If you rebuild it to match, it should work then with also the battery (when it is charged up).

[marce002]

Re: Apple A1425 retina does not power on after BAT depletion

ok then I interpret that should connect the source for that tiny power supply of 3.42 to both sides bat and charger? for example to F7040 one leg and the other to R7020 ... only problem would be battery depletion after some time unused because that power supply 3.42 will be always feed? but it will fix powering on because ac charger will be present.. right? thnks

[reformatt]

Re: Apple A1425 retina does not power on after BAT depletion

Which motherboard part number are you working with? If it's 820-3462-A then dual diode is D6905, not D7005 (different board number). You should let us know from the outset that the board has been modified to that of the schematic.

If you have directly connected the 3V42 supply from F7040, this a SNAFU. When battery is depleted, you won't have any PPBUS_G3H. With that absent, pin 1 of D6905 will provide power to the PP3V42_G3H circuit via the adaptor. You need to wire in a replacement dual diode from adaptor (via R6920/PP18V5_DCIN_ISOL) in addition to that from PPBUS_G3H, with the output feeding your modded 3V42 supply.

Cowboys.

[marce002]

Re: Apple A1425 retina does not power on after BAT depletion

hi reformatt it is 820 3462A and yes i will try your suggestion regarding pin 1 of D6905 will provide power to the PP3V42_G3H circuit via the adaptor.. thnks very much, apreciate it.