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A1466 (820-00165) No Chime, No POST

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    A1466 (820-00165) No Chime, No POST

    Good Day!

    History:
    The board was not booting, upon opening it the fan was spinning but there is no PPVCC_S0_CPU. PP1V05_S0 was 0.550v. PP1V05_S0 Diode Mode = 0.007v , Resistance = 3.4ohm. ALL_SYS_PWRGD = 3.340v. I suspected it was a short on the PP1V05_S0, so I lifted L7630 and found the 3.4ohm short on the Load Side. I injected 1v on the rail and it was only taking 34mA. After this I returned L7630 and investigated the U7600 (TPS51916). It has VREF (1.8v) and REFIN pins. And sure enough, the REFIN voltage is just 0.550v. That is why there is ALL_SYS_PWRGD, because it thinks it is doing its job. So, I measured the Voltage Divider resistors for the P1V05S0_FB. R7612 is out of spec. I removed it but then it was measuring correctly (50.1kohm). So I returned R7612 and removed U7600. Short on the PP1V05_S0 rail was gone. I soldered a new TPS51916, powered it on and now I'm getting 1.055v on PP1V05_S0. PPVCC_S0_CPU is also at 1.702v. Fans are spinning.

    Problem: No Chime, No POST

    Status:
    Magsafe = Green to Orange LED
    Fan = Spinning
    Image = None
    Backlight = None
    USB Mouse = No LED
    Caps Lock = No LED

    Shift + Power = Fan turns off
    SMC Reset = Fan turns off while holding keys and starts again on release
    PRAM Reset = No Response

    Board is very pristine.
    J6100, U6100, U1900 are very clean. Traces are good too.
    Tested SPI Termination resistors, all match value from the schematic.
    Probing SYSCLK_CLK32K_RTCX1, I get ~32kHz

    Voltages (I'm sorry if this is too much, I just want to put out as much information):
    PPBUS_G3H = 8.58v
    PP3V3_S5 = 3.343v
    PP5V_S5 = 5.101v
    PP3V3_SUS = 3.342v

    PCH_INTRUDER_L = 3.115v
    RTC_RESET_L = 3.359v
    PCH_SRTCRST_L = 3.354v
    PCH_INTVRMEN = 3.248v
    PCH_DSWVRMEN = 3.251v
    S5_PWRGD = 3.368v
    PM_DSW_PWRGD = 3.406v
    PM_BATLOW_L = 3.356v
    PM_RSMRST_L = 3.315v
    PM_PWRBTN_L = 3.403v
    SMC_ONOFF_L = 3.413v

    PP3V3_S4 = 3.336v
    PP5V_S4RS3 = 5.104v
    PP3V3_S3 = 3.341v
    PP1V8_S3 = 1.800v
    PP1V2_S3 = 1.202v
    PP5V_S3_RTUSB_A_F = 5.104v

    PP5V_S0 = 5.098v
    PP3V3_S0 = 3.339v
    PP1V05_S0 = 1.050v
    PP1V5_S0 = 1.506v

    P5VS4RS3_PGOOD = 3.339v
    P1V8S3_PGOOD = 3.340v
    DDRREG_PGOOD = 3.340v
    P1V05S0_PGOOD = 3.341v
    ALL_SYS_PWRGD = 3.346v

    CPU_VCCST_PWRGD = 1.019v
    CPU_VR_EN = 1.053v

    PPVCC_S0_CPU = 1.700v
    PP0V6_S0_DDRVTT = 0.600v

    CPU_VR_READY = 1.051v
    PM_S0_PGOOD = 3.410v
    PM_PCH_PWROK = 3.410v
    CPU_VIDALERT_L = 0.098v
    CPU_VIDSCLK = 1.050v
    CPU_VIDSOUT = 1.050v

    SMC_DELAYED_PWRGD = 3.406v
    PM_PCH_SYS_PWROK = 3.409v
    LPC_PWRDWN_L = 3.343v
    PLT_RESET_L = 3.344v
    PLT_RST_BUF_L = 3.336v

    EDP_PANEL_PWR = 0v

    SMC_LSOC_RST_L = 3.397v
    SMC_MANUAL_RST_L = 2.812v
    SMC_RESET_L = 3.370v
    PM_SYSRST_L = 3.337v
    CHGR_RST_L = 3.378v

    SMC_CPU_VSENSE = 1.698v
    SMC_P1V05S0_VSENSE = 1.055v
    PP1V05_SUS = 1.058v

    Is the EDP_PANEL_PWR supposed to go up after the POST? PPVCC_S0_CPU should also be 1.85v? What should I test for next? Thank you in advance!

    #2
    Re: A1466 (820-00165) No Chime, No POST

    Thanks for the detailed diagnostics, it covers almost everything, this is a pretty rare sight over here…
    It also means you already did most of the troubleshooting and there's little hope left to fix this one…

    Was there liquid or physical damage? No other hint on the board?

    It could be an issue with the EFI so you could try to flash the SPI ROM.


    EDP_PANEL_PWR won't come up at this point so for now you can ignore it.

    Exact voltage on PPVCC_S0_CPU at boot will vary from CPU to CPU so it's hard to say what's a good value and what's a bad value…
    However, on one of my board the voltage is supposed to be 1.76V at boot, and when the CPU wasn't communicating to the CPU VCore controller through SVID, it would be only around 1.69V, and the machine wasn't POSTing.
    It's probably be a dead end, but you can at least check voltage on both sides of R0810, R0811 and R0812, and check resistance across R7280, R7279, R0800, R0802, R0812, R0811 and R0810. If you have an oscilloscope you could also check if there's activity on CPU_VIDSOUT/CPU_VIDSCLK.
    OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

    Comment


      #3
      Re: A1466 (820-00165) No Chime, No POST

      Hello!

      Thanks for answering back. There was no liquid damage on the board. One night it was turned off. The next day it won't turn back on. That's it. Visual check reveals nothing at all. No corrosion.

      SPI ROM is next on my list. I'm still waiting for my CH341A, it should arrive by tomorrow. I'm currently watching your Instructional Videos regarding Clean ME & Change SSN. You're the man! Would it be possible to flash SPI ROM In-Circuit (Test Points)? If not, I'll just remove U6100 and put jumper wires in place. Is it possible to use SPI Flash Chip in SOP-8 package connected to the jumper wires for trial and error of BIOS files? I'm going to cook up at least 3 BIOS files for testing.

      I will test those Voltage/Resistors you posted. Regarding the signals, maybe I'm missing something else? I'm not familiar with Power Sequence of macbooks. I've read just about everything in rossman forums and here about A1466 boot problems. But I'm sure what I know is not yet enough.

      What comes first, SPI ROM communication or SVID communication? For CPU_VIDSCLK, should there be a constant pulse there. I'm only getting constant pull-up voltage, maybe it stays up when CPU doesn't want VCore adjustment?

      I probed the SPI_CS0_L line and got this result:
      https://ibb.co/wRhjJQ9

      Here's for the SPI_MISO_R:
      https://ibb.co/h9YVvVL

      Would this mean PCH is trying to access data. I get same reading every power cycle.

      Thanks again!
      Last edited by cevar_blackwing; 11-04-2020, 04:00 PM. Reason: links

      Comment


        #4
        Re: A1466 (820-00165) No Chime, No POST

        About flashing the SPI ROM, there are cables that can connect to the J6100 connector but they are expensive (more than $60). Medusa2 is also a pretty handy device that can do it, but cost is only justified when you do Mac logic board repair regularly. Otherwise a programmer like RT809F or TL866II with a WSON8 adapter board does the job fine. CH341 can do it too but I regularly see people having issues with it so I don't recommend it. Also flashing in circuit can sometimes cause issues so desoldering the chip is a safer bet.
        Start by flashing a known good dump for an 820-00165 board without worrying about ME region or ssn. Once you confirm it at least chimes you can clean ME region and edit serial number.

        About the power sequence, you can take a look here:
        It's not necessarily complete and 100% correct but still gives a rough idea.

        To clarify, the first communication with SPI ROM happens between PCH and SPI ROM only — CPU is not involved. PCH reads soft straps at that point. In general (don't assume it's always the case though) the board will power cycle if PCH gets to the point of reading soft straps from SPI ROM but it fails for whatever reason.

        After PLT_RESET_L comes up the CPU will start processing instructions from SPI ROM, so you get another window of activity on SPI ROM which is the CPU reading EFI (the request goes through the PCH still).
        You can see some oscilloscope captures of what CS# pin could look like here: https://logi.wiki/index.php/EFI
        Pay attention to the horizontal scale. In general you can set your oscilloscope to trigger single shot on falling edge when probing the CS# pin. Your oscilloscope has probably a pretty low bandwidth so you'll not see something as clear as the pictures behind that link (they are taken with 100MHz I think).

        CPU communicating with CPU VCore controller over SVID is not required for PLT_RESET_L to come up. I don't know at what point the CPU tries to adjust VCore though.
        I don't know how SVID works (that's something I should probe to see the correct behaviour), but I guess the clock signal isn't driven when the CPU doesn't need to communicate with CPU VCore controller.


        PS: Just noticed that but you got post n°1000000… sorry there is nothing to win unfortunately. :x
        OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

        Comment


          #5
          Re: A1466 (820-00165) No Chime, No POST

          I'll try to flash the SPI ROM with the CH341 and WSON8 adapter first. And maybe, verify the flash multiple times. I don't want to buy the J6100 connector as I don't regularly repair macbooks. Do you happen to have a link for a known good dump for 820-00165? I've got the "2017 clean ME - fixed.bin" and "820-00165-A clean ME.bin" floating around the net. Are they good though?

          Thanks for clarifying the Power Sequence more to me. That link helped a lot. Regarding the SVID information, does it pull Voltage IDs from the SPI ROM or the CPU has it and provides this info to the VCore Controller?

          Regarding the pictures I posted, they were captured using a cheap Oscilloscope and can only go max 200kHz. So I really can't compare it with those done with good equipment. What I'm looking for is just some conclusive evidence that there really is an activity going on between the PCH and SPI ROM. Just to rule out a dead PCH. What do you think? And also, do you know how fast the SPI ROM ClK is running? Is it 25Mhz?

          post n°1000000 - What do you mean?

          Comment


            #6
            Re: A1466 (820-00165) No Chime, No POST

            I don't have a good 820-00165 dump (never worked on that board model) but try to find one here or on Rossmanngroup forums that someone confirmed working.

            The voltage tables are programmed inside the CPU itself. I don't know if the CPU needs to talk with the SPI ROM to set its voltage though, since software can select a different setting through CPU MSR.

            SPI ROM clock should be at 50MHz, so you'd need a 100MHz scope to see it properly.
            Also on 820-00165 it runs in Quad SPI mode so data is spread across the 4 I/O pins when doing a read operation (so decoding the signal just on MISO wouldn't be enough to read the actual data — not that it really matters since it wouldn't make much sense without knowing exactly how the EFI is built).


            Your original post has id n°1000000: https://www.badcaps.net/forum/showpo...00&postcount=1
            OpenBoardView — https://github.com/OpenBoardView/OpenBoardView

            Comment


              #7
              Re: A1466 (820-00165) No Chime, No POST

              Hi mates,
              Try this dump.
              PS: rename it to ( .bin ) extension.


              Attached Files

              Comment


                #8
                Re: A1466 (820-00165) No Chime, No POST

                I already found 2 SPI ROM files in rossmangroup & this forum.

                The CPU probably needs a go signal from the PCH after it has POSTed to set the CPU VCore. Maybe that is why I'm still on 1.7v.

                I can't justify a purchase of 100Mhz Oscilloscope, so I'm gonna stick with my cheapo one. No need to decode the SPI data, just knowing that there is activity is fine with me.

                My CH341A isn't here yet, so I'll probably put a hold on this repair. I'll update you guys for any changes. Or if you get any idea on which to test, please tell me. Thanks!

                @aynassour
                Thanks for the upload!

                Comment


                  #9
                  Re: A1466 (820-00165) No Chime, No POST

                  Originally posted by cevar_blackwing View Post
                  I already found 2 SPI ROM files in rossmangroup & this forum.

                  The CPU probably needs a go signal from the PCH after it has POSTed to set the CPU VCore. Maybe that is why I'm still on 1.7v.

                  I can't justify a purchase of 100Mhz Oscilloscope, so I'm gonna stick with my cheapo one. No need to decode the SPI data, just knowing that there is activity is fine with me.

                  My CH341A isn't here yet, so I'll probably put a hold on this repair. I'll update you guys for any changes. Or if you get any idea on which to test, please tell me. Thanks!

                  @aynassour
                  Thanks for the upload!
                  Hi, did you sort in the end? If so, how? I have the same issue... all my rails are fine, green light, orange, fan spin power on but no chime. SMC reset works. But my PPVCC_S0_CPU is 1.68-1.69V...... No idea what to try next...

                  Comment


                    #10
                    Re: A1466 (820-00165) No Chime, No POST

                    Hello
                    So I have this a1466board 820-00165 and for some reason the moment I put the adapter the green turns orange
                    Ppbus 8.55v
                    G3hot 3.42
                    3v3 3.3v
                    5v come for a sec and drops and second attemp and then nothing
                    So I notice S0 S3 S4 states come on power all for just a sec and turn off
                    I see vcore 1.78v come and drops . I have changed smc with a good one also checked all sys pwrgd all seem okay
                    Now if I disconnect my 3.3v S0 load switch everything stay on except no vcore ofcourse . I have checked spi resistors generally always bad or open traces but this is also good and tried a good known efi.
                    Yesterday I removed a resistor which does not allow it in quad mode so I get my machine on with all voltage perfect even vcore except no display and I see my load switch for S0 is 2.8v some leakage may be load switch issue.
                    How do we disable the quad mode or has some one change the spi chip to another no
                    Thanks

                    Comment

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