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  1. #1
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    820-3462-A no green light

    Using 60W charger, works ok on other Macbook, there are ok reading for dc in, ppbus_g3h, sms_bc_acok, pp3v42_g3h, adapter_sense., sms_reset_l. I thought that those would be enough to get a light on the charger.
    There are a lot of others that I measured and were ok. I will measure exactly again tommorow because I forget to write it all down.

    What is not ok is all PP5V_S0, S3, S4, S5 rails are 0v. What should I look for?

    Thanks in advance for help

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    Re: 820-3462-A no green light

    Try a different DC in board.
    To get a green light on a charger, you must have a pp3v42_g3h line and SMC that is communicating with charger.
    Without that, the laptop will not boot, even if you have PPBUS_G3H.

    What is the voltage on PPBUS_G3H?

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    Re: 820-3462-A no green light

    I don't think it's dcin board, all readings from charger are ok. Wil check it thought later (don't have spare here).
    Readings:
    PP3V43_g3H = 3,426V
    ADAPTER SENSE - 3,01V
    SYSYONEWIRE - 3,01V
    PPBUS_G3H_R - 12,3V
    PP18V5_DCIN_FUSE - 16,46V

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    Re: 820-3462-A no green light

    I had a DC in board that tricked me, it was a 2011 MBP. The duo diode was blown and it prevented the SYS_ONEWIRE signal to pass to charger. But it is rare on Retina models that the DC in board would fail. But it happened on multiple occasions, the board came in, they said it was looked by another shop, saw they replaced an ISL chip. Changed the DC-in board and it worked.

    Check the middle pin on the MagSafe connector itself if it is getting the 3.4V.

    The PPBUS_G3H voltage is not correct! It should be 12.60V. That means the communication between SMC and charger is not established. First get that to work, this will most likely bring back the green light and get it to boot. You could have a bad SMC here...

    Was there any liquid damage?

    What is the voltage on SMBUS_CHGR_SCL and SMBUS_CHGR_SDA lines? Are they pulsing or are 100% stable?

  5. #5
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    Re: 820-3462-A no green light

    Possible SMC issue if your PPBUS_G3H is 12v3..

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    Re: 820-3462-A no green light

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    Check the middle pin on the MagSafe connector itself if it is getting the 3.4V.
    It's getting 3,01V (but I measure on the pins on dcin board, on the magsfe itself it gives me unstable voltage). Charger is fine with another retina Macbook.

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    The PPBUS_G3H voltage is not correct! It should be 12.60V. That means the communication between SMC and charger is not established. First get that to work, this will most likely bring back the green light and get it to boot. You could have a bad SMC here...
    Thanks, I feel so stupid, I don't know why I thought 12,3V is ok.

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    Was there any liquid damage?
    Nothing obvious and that is a motherboard with attempt of repair. I see two small probe points near SMC that could indicate there was slight water damage.

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    What is the voltage on SMBUS_CHGR_SCL and SMBUS_CHGR_SDA lines? Are they pulsing or are 100% stable?
    Both are 0V, but I'm not connected to battery, only charger.

    Of course SMC_RESET_L 3,4V.

    Can I somehow check for sure it's SMC?
    Last edited by Rauliki; 07-19-2019 at 08:34 AM.

  7. #7
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    Re: 820-3462-A no green light

    PP3V43_g3H is 3.42V.
    I am a bit puzzled why you are getting 3.0V on the MagSafe board.
    Also you said it was pulsing. I usually measure on the dc in board itself, you can easily poke with a probe to pin on the magsafe board. If it is unstable there, if this would be me, I would really want to change it, just to be sure.

    SMBUS_CHGR_SCL and SMBUS_CHGR_SDA are 0V? Check diode mode on them and see if they are more than 1% different. They should be 3.42V with occasional pulses that could be seen on voltmeter. There are resistors that connect these two lines to the PP3V43_g3H line, check them if they are in spec (sadly I am on vacation and don't have schematics with me).

    If there was any water damage near the SMC, I would begin obtaining a replacement SMC...

  8. The Following User Says Thank You to mitchW For This Useful Post:

    Rauliki (07-26-2019)

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    Re: 820-3462-A no green light

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    PP3V43_g3H is 3.42V.
    I am a bit puzzled why you are getting 3.0V on the MagSafe board.
    I measured it with different dcin_board and it's the same 3,01V. I don't have any other to measure

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    Also you said it was pulsing. I usually measure on the dc in board itself, you can easily poke with a probe to pin on the magsafe board. If it is unstable there, if this would be me, I would really want to change it, just to be sure.
    It's stable on dcin board but 3,01V.

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    SMBUS_CHGR_SCL and SMBUS_CHGR_SDA are 0V? Check diode mode on them and see if they are more than 1% different. They should be 3.42V with occasional pulses that could be seen on voltmeter. There are resistors that connect these two lines to the PP3V43_g3H line, check them if they are in spec (sadly I am on vacation and don't have schematics with me).
    it could have been I didn't push probe on pins. Anyway, they were very dull not shinny so I made them look better and both are 3,42V but I couldn't see any pulse. Both was pretty much stable.
    I wil try to find those resistors tommorow.

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    If there was any water damage near the SMC, I would begin obtaining a replacement SMC...
    I could probably try to rebal SMC, I haven't seen any for sale lately.

    Thank you and have a nice vacation.
    It's not that I'm in a hurry, I doing this as hobby (for now), this feeling when you repair a dead laptop is really nice and rewarding.
    If you have a Paypal maybe I could send you some money for a good beer as a thanks?

  10. #9
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    Re: 820-3462-A no green light

    Thanks for the info.

    PPBUS_G3H being 12.2-12.3V means the ISL (U7000) is not communicating with the SMC. This could also mean the SMC is good, but it is being unable to communicate to charger. I replaced a SMC before, only to find out the DC-in board was flakey.

    ADAPTER_SENSE is 3.42V? Just checking... this line goes to the DC-in board and it should be 3.42V there. If it is just 3.00V as you wrote, then this might be a problem. There is a dual diode (3 pin part) that often goes on the dc-in board. Measure in diode mode with the red probe on the top pin and black probe on the left and right bottom pins. You should get almost the same results. There are also two resistors there, if any of these fail, it will almost 100% result in no green light.

    The pullup resistors on SMBUS_CHGR_SCL and SMBUS_CHGR_SDA are 99% good as you are getting nice 3.42V there. These are R5280 and R5281, both are 2K ohms. Better test is to measure the diode voltage drop on these lines, do the same as I wrote for the diode on the DC-in board. Red probe on ground, black probe on this line. Both of these lines should read almost the same (1% apart).

    Before you go and replace the SMC... can you get the machine to start in SMC bypass mode? You hold the power button, connect the adapter, continue to hold it down for 10 seconds, release it and press briefly again.

  11. #10
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    Re: 820-3462-A no green light

    Quote Originally Posted by mitchW [Only Registered and Activated Users Can See Links. Click Here To Register...]
    ADAPTER_SENSE is 3.42V? Just checking... this line goes to the DC-in board and it should be 3.42V there. If it is just 3.00V as you wrote, then this might be a problem. There is a dual diode (3 pin part) that often goes on the dc-in board. Measure in diode mode with the red probe on the top pin and black probe on the left and right bottom pins. You should get almost the same results. There are also two resistors there, if any of these fail, it will almost 100% result in no green light.
    There is 10% difference, one is 0,670V and the other is 0,605V (pretty much the same for both dc in boards).
    You wrote that it should be 1%.

    The pullup resistors on SMBUS_CHGR_SCL and SMBUS_CHGR_SDA are 99% good as you are getting nice 3.42V there. These are R5280 and R5281, both are 2K ohms. Better test is to measure the diode voltage drop on these lines, do the same as I wrote for the diode on the DC-in board. Red probe on ground, black probe on this line. Both of these lines should read almost the same (1% apart).
    I will check it tommorow. Thanks for suggestion.

    Before you go and replace the SMC... can you get the machine to start in SMC bypass mode? You hold the power button, connect the adapter, continue to hold it down for 10 seconds, release it and press briefly again.
    This A1425 are p... in the a.. to disassembly and assembly. As I have board disassembled now I would try everything else first.

 

 

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