Macbook Pro M1 820-02020 - no display

[obelix24]

I got one MacBook Pro M1 that was water damaged.

It was not turning on I've changed one CD3217 IC and now MacBook is taking 5V instead of 20V, I've also replaced U5700 as there was clicking sound when charger was connected.

But MacBook turns on (when I connect charger it's taking only 5V 0,04a) but there is chime and when I connect external screen over HDMI I can see login screen. Trackpad is working, keyboard backlight is also working and keyboard looks also ok (but not tested fully)

Issues are :

Touchpanel is of there is no sign of life...
Internal display is not working but previous owner told me that screen should be ok. He gave this MacBook to two other people to check and each of them make something (but it looks like no board level repair was done by them)

I'm trying to find out if the screen is ok.

I've checked
PP1V8_AON - stable 1.8V
PP3V8_AON - stable 3,8V

Is there anything that can cause no Touch Bar and no internal display only external ?

[obelix24]

I've checked
PP1V5_UPC0_LDO_CORE - 1,5V
PP3V3_UPC0_LDO - 3,3V

PP1V5_UPC1_LDO_CORE - 1,5V
PP3V3_UPC1_LDO - 3,3V

FF200 on both sides stable 20V
FF201 on both sides stable 20V

But on all CP870, 71, 72, 73, 64, 65, 66 (PPVOUT_LCDBKLT - 0V (but i don't know if screen needs to be connected when testing this) - here no screen connected

Also on L5230 on both sides i don't have stable V .... CHRG_PHASE1 and PHASE2

on F5200 - both sides stable 12,04V

[obelix24]

I've checked with screen connected and same result.

Also between LCDBKLT_FB (PIN2 on RP831) and PPVOUT_LCDBKLT there is no continuity, there is resistance 17k Ohms

also one more thing this macbook came to me without display flex cable so i found one that looks same but it's probably from a2189 or a1708 is this problem ?

[obelix24]

any idea anyone ?

[mon2]

also one more thing this macbook came to me without display flex cable so i found one that looks same but it's probably from a2189 or a1708 is this problem ?

Not recommended unless you are 100% sure it is the same. We have faced a similar issue with trackpad cables where the width of the cable was 100% but the pad to pad pitch was different than the original so the # of contacts did not match and respectively, the trackpad failed to function.

Find a known good cable for the actual unit under test.

[obelix24]

I've ordered new flex at monday i will have it so i will check

[obelix24]

ok today I've got the flex finally
I've installed it and I've turned MacBook on and I can see image but no backlight.

I've checked
PP5v_BKLT_A and PP5v_BKLT_D - both 5,2V (stable)

but I still don't have continuity between pin 2 of RP831 (LCDBKLT_FB) and PPVOUT_LCDBKLT - there is resistance 17k ohms

PPVIN_LCDBKLT_F - is 12V
BKLT_EN_R - 0V

[mon2]

Measure the voltage to ground on QP800. Post each measurement.

[obelix24]

pin 1 - PPVIN_LCDBKLT_Q - 0V
pin 2 - PPVIN_LCDBKLT_Q - 0V
pin 3 - LCDBKLT_EN_L - 11,94V
pin 4 - PPVIN_LCDBKLT_R - 12,04V
pin 5 - PPVIN_LCDBKLT_Q - 0V
pin 6 - PPVIN_LCDBKLT_Q - 0V

[obelix24]

as checking schematics it looks like that CP801 and CP810 should be responsible for transferring voltage from LCDBKLT_EN_L to PPVIN_LCDBKLT_Q so most probably one of this should be wrong ? I have to check when i will be home

I've tried also diode mode (red on ground black on pin)
on QP800 on ping 1,2,5,6 - 0,899V
PPVOUT_LCDBKLT (CP869,CP868,CP867,CP860,CP861,CP862,CP863) - 1.2V (does this mean there is short on this rail ? maybe inject voltage ? 1V 3A ? or never inject voltage to this rail ?

[obelix24]

mon2 what do you think ?

[mon2]

What is the voltage to ground of BL_PWR_EN? This must be a logic '1' or at least 1v2

Voltage to ground of PP5V_S2 ?

The mosfet @ QP800 is acting like a switch from the main power rail to feed into this backlight circuit. QP800 is a P-channel mosfet so this will require the GATE voltage to be lower than the voltage being passed between source / drain pins. At this time, the gate voltage is the same as the SOURCE which results in keeping this mosfet OFF.

To enable this mosfet, the gate voltage must be lower and this is lower voltage is created by the voltage divider built by RP801 & RP802. That is, RP802 must be grounded through the backlight IC @ UP800.

For now, start with the check to see if the backlight is being enabled.

[obelix24]

PP5V_S2 - 5,2V
BL_PWR_EN - 1,8V

[obelix24]

mon2 it looks ok.
so this means that most probably UP800 is faulty ?

[mon2]

Perhaps. Carefully, with a piece of wire - connect one side to the gate pin of the mosfet at qp800. The other side of the wire to ground. This action will force the p-channel mosfet to enable. Be sure to study which pin is the gate pin (pin #3) before attempting.

Post your results.

[obelix24]

mon2 I've tried what you mentioned carefully connect pin 3 of QP800 to ground and turned on but still no backlight. Picture was visible but no background as before

[obelix24]

I've ordered spare board a2338 to have spare parts. When it will arrive i will try to replace UP800 if this fix issue with backlight. Also i have to replace cd chips as it's taking only 5v

[obelix24]

Today i've received donor board ... I tried to replace UP800 but still no backlight I'm really out of clue what can case this problem
Also MacBook is taking now 19V on both ports.

[obelix24]

according to schematics RP844 and RP845 should be 0ohm ?
both are 10ohms in my case

On one side of RP844 and RP845 I have 5,2V and on other side 5,1V

I'm thinking if I should not try to use wire so there will be 5,2V on input and also on output. To see if this is not causing problems. But I don't want to damage MacBook more ... Does anyone have fully working A2338 where can be checked resistance of RP844 and RP845 ?

[mon2]

I think you are ok here for the resistance values.

BKLT_EN_R - 0V

So the board is not requesting for the backlight to be enabled. Check the voltage to ground of:

BL_PWR_EN ; the other side of the 0 ohm resistor
IPD_LID_OPEN_1V8 ; the signal that will be used to decide to enable the backlight or not and is linked to the hall effect sensors inside of your trackpad


Carefully also confirm the voltage to ground for:

I2C_BKLT_SCL
I2C_BKLT_SDA