820-01987 20v 0.019A pp3v3s5 pulsing

Hi all,

Need some assistance with a 1987. History is its chassis was completely crushed trackpad and screen were shattered not sure how but it seems like it was ran over. Board visually seems fine doesn’t look warped no visible cracks in anything board side.

went through the power sequence diagram on logiwiki for the 01055 because there doesn’t seem to be one for the 1987? All rails up until pp3v3s5 are present. Found out that pp3v3s5 and pp1v8s5 are coming on when you first connect the board but they shutdown after around 15 seconds or so.It seems like the PMIC is detecting a short on a minor sub rail and shutting down.

so the question is are there any signature faults with the PMIC and the 820-01987? Unfortunately I do not have a thermal camera so I’m hoping there’s a shortcut I can follow. Freaking seeks have gone from 500 to 900 hence why I’ve been putting it off, not to mention we don’t do much of this so it’s hard to justify spending a grand for a once in a blue moon job.

thanks for the assistance!

Has anyone else noticed the board view labeled 820-01987.bvr doesn’t seem to match the board? Been looking at the PMIC lines to see what could be shorted and a lot of the component locations don’t match the board. Especially test points.

Noticed 3 test points are reading as ground when they’re supposed to be PMIC outputs. One in particular p1v1_slpddr_socket_en. I’ve attached a pic with the 3 test points reading as ground outlined. Not sure if there the right test points though as they don’t line up with the BV.

Test points figured on the boardview are not always available on "real life".
It happens on other models too; even old ones.

Is the machine recognized in DFU?
Did you check diode mode to ground on all coils?
Apart of S5, can you detect any S3, or S0 voltage?

I suspect broken trace/solder, or knocked off components.

Thanks, thought as much. I noticed the same when I was working on that 1958 a while ago. The large cap on the left side of the nand in the photo above is C8751 what do you think those three TPs with the blue squares are? Being behind the CPU there probably supposed to be quite low resistance I'm guessing, but not 0.002 ohms so I'm guessing there what the issue is but unfortunately the only other way to test those lines is remove the T2/PMIC shield which I really want to leave as a last resort.

Sorry forgot to mention that in the original post. It is not recognized in DFU. That said the only mac we have is a A1708 which only will upgrade to Monterey, I tried upgrading it further, but it says it's not supported via the app store so not sure if you can "force" upgrade these or not. I did use the master port on the 1987 and tried both ports on the A1708. I have not tried forcing DFU via the test pad because the rails were shutting down I assumed there's further board level faults not firmware faults.

Yes I checked diode mode on all the coils. The CPU ones seem a little low comparing them to open board data, but there within 15% which I'm hoping is just meter differences/board differences and not a dead CPU. Is this board one of the ones that is required to have a working CPU to get 20V?

Just checked now yes S3 & S0 are also pulsing. Checked PP1v_s3 & PM_SLP_S0_L. I did not check them earlier as the S5s were pulsing.
Somethings burned out as when I went to check ALL_SYS_PWRGD the USB C meter now is only outputting 5V 0.200A in all 4 orientations of the usb c cable.

Damaged tracks definitely but I doubt it's a knocked off component. Physically board looks fine, normally if there's knocked off components you can see a part of the pad or the component torn or remaining, but everything looks normal. There are some components "missing" for example R5929 that whole row is missing and not marked as no stuff in the schematic. As is the row of R5569. As are the caps in the vertical assortment in between those row's ex C5569 and again not marked as no stuff in the schematic.

Think my USB C meter is trolling me. Disconnected power from it a few times and it was still stuck on 5V. Switched orientation of the power in cable and it went back to 20V than I disconnected the board and reconnected and it sat on 5V for a while till I went back to the original orientation. Time for a new USB c meter, freaking China!

I am getting ALL_SYS_PWRGD & SMC_PCH_SYS_PWROK for a brief moment and PLT_RST_L is 0v consistent so it's stuck in a reset state.

Did you test the board alone on the desk?
It should boot with correct charger.

Must be recognized in DFU, if T2 required AWAKE and SLPS2R voltages are stable.

Yes all the above findings are with the board only. Nothing, but a 98W apple charger and apple cable connected so that side should not be a issue. I haven't tried without the usb c meter though so I could try that but then you would have no indication of boot unless I connect it back into the chassis.

PP1V8_AWAKE dips down for a split second once the PMIC shuts off but comes straight back up and is stable. PP1V8_SLPS2R does the same. Once the PMIC shuts off the board settles into 20v and bounces between 0.0138-0.0161a.

All signs are indeed pointing to T2 firmware issues, so is it worth forcing the device into DFU mode? It does not seem to be in DFU mode itself so it will have to be forced. I do not want to do this though as I'm concerned the A1708 I have won't be able to detect it. Looking at both logiwiki and the repair wiki both note you must be on the latest MAC OS which obviously the A1708 does not support. Unfortunately, we don't have any newer macs to use.

Why will need you USB-C meter to confirm boot?
Measuring CPU core voltage is not good enough?

Is worth to force DFU mode.
Check SOC_DFU_STATUS, to get an idea about actual board state.

I managed to get our A1708 onto the latest OSX through legacy core patcher so I'm going to try forcing the board into DFU mode. For Apple Configurator though has Apple Configurator 2 been replaced with just plain old Apple Configurator? I can't find 2 on the app store and googling it there's forums pointing back to use plain Apple Configurator but all the DFU tutorials call it 2 so I'm not sure if I've downloaded the correct version.

Dfu restore failed (yes I know it deletes data that’s what I wanted).

It’s now saying apple controller instead of dfu. Tried it again and got a different error this time

Ha I feel like I'm the pin ball at a roulette table. Tried putting the board in DFU mode again and now recieved error 75.

Finally seems to of gone through now I’m at a lock icon?

That looks good.
The target MacBook didn't boot?
Still pulsing voltages?

It didn’t boot no, 20v fluctuates around 300ma didn’t check the rails had to head home. took the board and chassis home with me to try out it back together over the weekend but I forgot to grab the charger,multimeter and screws. Might try hookup the battery flex tomorrow and hold down the battery flap see if that boots otherwise I’ll have to wait till I’m back in the office on Monday.

It's still doing the same thing. ALL_SYS_PWRGD comes up to 1.8V for about 20 sec when the boards taking 0.5 amps than once it dips down to 0.01 it drops out. Do these require a battery to boot or complete DFU restore? I was originally doing it board only and kept getting -75. Read Logiwiki and it mentioned trackpad and battery must be connected but I didn't have the battery ribbon, so I just connected trackpad and that's where I got the above lock screen. I've got the flex now so is it worth putting the board back in the chassis and connecting battery and TP to retry DFU?

Yes, try DFU with battery connected too.

Looks like the CPU is dead . Connected the battery and trackpad and it would refuse to be detected in DFU mode despite the detect signal being present. Disconnected the battery and trackpad and connected the fan because I noticed the CPU heatsink heating up slightly and now can't get past 5V 280ma on all ports besides the trackpad side one way the connector gives 5v 280ma, the other way the board does not turn on at all, XAVbus fuse near the corresponding CD is 0v and the board takes 0 amps. Tried without my USB C meter as well to make sure that wasn't trolling me again than checking the fuse near the CDs to check whether it's 20V or not and there still 5V.

Checked the CD3217 LDOs all of them seem present, so either the ISL has gone or me leaving the battery connected for a while to charge up killed something.

You don't get PPBUS_G3H now?

PPBus at F7000 is 1.28V for about 40 seconds then the board shuts off and obviously drops to 0. That's if I reset the charger and it's at 5V. If I use another device to switch the charger to 20V than connect the board sits at 0.0035 ma and 20V which looks like DFU mode but it's not, DFU status is not present.