A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-02016

[slimmy182]

MacBook Air A2337, logic board number 820-02016-A . Long story short, this Air was display damaged with no image and no backlight at all but internal webcam was working , all other parts seems to be in good working condition. Trying with a know good working original Display show image but have no backlight at all and now also internal camera and ALS (Ambient Light Sensor) is not working anymore.

Inspecting the logic board I found this bad looking smd component just under the display connector, but I haven't schematics, can you help me please identify it to be proper changed?

Thanks

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Hi. See attached. The damaged part (@LP670) is a very low cost ferrite bead (0402 size; 120 ohm @ 1.5A). In a pinch and for testing, you can remove the damaged part and short the 2 pads. This should fix your webcam fault.

Otherwise, Arrow will have these. If you need a few, can drop ship them to you. Send me a PM.

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

On the backlight missing - see attached. Proceed with caution due to the very dense PCB layout.

Measure the voltage on any of the bulk caps that should offer the backlight voltage for the LCD panel. What is the voltage reading for your logic board?

If you do not see 25v+ volts here then remove all power.

Meter in resistance mode (2k setting)

Red meter probe on the same (any of the bulk) caps.

Black meter probe to ground (shield is ok).

What is the resistance to ground ?

If the resistance is low then you have a bad cap or short on the backlight voltage.

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Hi mon2! Thank you so much for the crystal clear explanations, I really appriciated your help!

Voltage reading of the bulk caps offer the backlight voltage is 0V

resistance to ground = 0.55

voltage on backlight fuse FP800 is 12.2V both before and after, beep in continuity mode.

There is anything else I can do?

I haven't tried it yet to short the two @LP670 pads to test webcam functionality.

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

1) Can you review and post the resistance to ground again? Remove all power to the logic board. Meter in resistance mode (2k should be ok).

Red meter lead on the requested (any) bulk caps.

Black meter lead on ground.

The resistance should be in ohms. What does the meter show ?

It is ok if it is OL (over the limit of the 2k) - you can then select the next higher resistance setting on your meter till you have a reading. Higher resistance is a good sign on that rail.

2) As you have no voltage on the backlight rail, either the backlight IC is not being enabled or the I2C communication lines are not working as they should. The communication lines are 2 interface lines used in the digital logic world to select a value for the slave device. One is used as the CLOCK (SCL) and the other as the DATA (SDA). The slave device here is the backlight IC and the host CPU will stream out values to light up the panel. Each I2C slave has an unique address on the I2C bus. Respectively, when you increase / decrease the backlight intensity, it is this pair of communication lines that define the LED configuration used by the LCD panel.

Have seen cases where these I2C lines are being strapped to a logic low for other reasons which can halt this 'party' rail from working.

Check as follows:

Meter in DC voltage mode (20V scale should be ok).

a) Carefully connect the red meter probe to RP842 resistor. Once you locate this part - check the voltage on BOTH sides of this 0 ohm resistor. With 0 ohms showing in the schematic - this is just a jumper so the reading should be the same on either side of RP842.

Black meter probe to ground.

What are the voltage readings here ?

We need to know if the voltage is high enough to ENABLE the backlight IC.

b) Repeat the same voltage testing for the I2C lines:

I2C_BKLT_SCL (2) - in the attached drawing
I2C_BKLT_SDA (3) - in the attached drawing

What are the voltage readings for each of these 2 lines ?

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Again, thank you so much for the support and for spending your time helping me and explaining all this stuff in this helpfoul and kind manner.

1) resistance to ground of the bulk caps offer the backlight (CP860) =
20k mode = 0.05 ohms, 2k mode = .056 ohms, 200 mode = 56.3

Is that a short to ground?

2) DC voltage RP842 = 0V both side
also CP842, both pin 0V

3) I2C_BKLT_SCL = 5.21V
I2C_BKLT_SDA = 5.21V

ALL measures are taken with just board alone and DC chord, no display connected or other things.

An other interesting thing is that when I turn on the computer on external monitor without the internal display assembly, not connected at all, the mac still show internal display in the pheriperical connected (see attached). I don't know if it's due to a different managment of display for this A2337 M1 model, but the same year intel Air A2179 behavour is different: if I disconnet internal display and use only external one it does not detect anymore the internal display.

I already tried DFU revive and restore but it doesn't help

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

1) resistance to ground of the bulk caps offer the backlight (CP860) =
20k mode = 0.05 ohms, 2k mode = .056 ohms, 200 mode = 56.3

Is that a short to ground?

Yes, this resistance @ ~56 ohms looks low for this rail.

You may have a bad capacitor on this rail OR the issue could be inside the LCD panel itself.

To confirm, always with all power REMOVED from the logic board - disconnect the LCD panel (if it is mated to the logic board).

Again with no power - meter in resistance mode (2k is ok) - check the resistance to ground of CP860 (since the group are together - this is a good one to use).

Do you still see about 56 ohms to ground resistance ?

If yes, carefully with that great microscope of yours - zoom over each and every cap in this cluster. Look for a possible damaged / cracked / off color capacitor. If they all look to be mint, then it may be worthwhile to remove the diode @ DP800.

Just lift up one leg on DP800 so that it does not impact the meter readings for the resistance checks. Then check again, what is the resistance @ CP860 ?

Still ~56 ohms ?

2) DC voltage RP842 = 0V both side
also CP842, both pin 0V

This is the ENABLE pin for the backlight. With 0v on this line = the backlight IC has been instructed to remain OFF.

This voltage could be low due to the driver pin for this line or this line has a fault with too much of a load.

Remove all power. Meter in resistance mode (2k is ok). Check the resistance to ground for this line.

Post the reading.

3) I2C_BKLT_SCL = 5.21V
I2C_BKLT_SDA = 5.21V

These are good values.

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

1) resistance to ground of CP860 56 ohms, both LCD connected or disconnected.

Unfortunately I don't see any sing of damaged / cracked / off color capacitor in this cluster.
I removed DP800 diode using rework hot air gun,

resistance to ground of CP860 now is 43 ohms.
It's stay 43 ohms even after put back DP800 diode. This could be the hot air worsening the short to ground?

2) resistance to ground for ENABLE Backlight

pin 1 CP842 = 1 ohms
pin 2 CP842 = 0.00 ohms

pin1 RP842 = 1 ohms
pin2 RP842= 1 ohms

1 ohms is the reading on Multimeter display in 2k mode, and it's the same results as when the probe are not touching anything, like there is no continuity
I re-mesured a lot of times, same results.

I attach here magnified photos of the only suspect cap I found explorating the board, but I guess they are not related to this issue, and a magnified photo of the LP670 blown camera filter

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

1) Remove each of the damaged parts and test the resistance to ground again. See attached.

One is cracked. The other is burnt.

2) Post the resistance to ground of the cap cluster which looks liquid damaged.

3) After the above, check the resistance again on RP842. RP842 is a 0 ohm resistor / jumper. Carefully with low air pressure but with high heat, remove RP842 with tweezers. Then RP842 will be removed out of circuit.

Next, with RP842 off the logic board - measure the resistance to ground of both SMD pads for RP842. Which side is showing the very low resistance to ground ?

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

1) removed both damaged parts, resistance to ground of CP860 group caps still being 43 ohms.

2) resistance to ground of the cap cluster which looks liquid damaged
@CR607 1.579 ohms, same on CW14A

3) with RP842 removed out of circuit neither pad 1 or pad 2 give me a value, still 1 on multimeter display. Only pad 2 CP842 show = 0.00 ohms

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

The '1' reading could mean that your scale for the resistance is too low.

Configure the meter to be the higher scale till you have a reading.

Post again.

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

The '1' reading could mean that your scale for the resistance is too low.

Configure the meter to be the higher scale till you have a reading.

Post again.

Is the same thing I tought, even using all the scale same results. Sometimes, but very rarely, seems to "bumbs to 1.890" before come back to '1' when switching from pad 2 to 1, but if I stay firmly in one pad just display '1'.

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

CP842, pad # 2 = Ground in the design. So this makes sense that the meter is showing 0 ohms for the reading.

On your meter, the resistance on pad # 1 (CP842) = 1 ohms ??

What is the resistance for RP842, pad # 1 ?

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

exactly, the resistance on pad # 1 (CP842) = '1' ohms

resistance for RP842, pad # 1 = '1' ohms

maybe that's could be a sort of 'OL', becouse 1' ohms it's the same measure displayed in resistance mode when probe are not touching anything!
I checkd also continuity mode and i've got continuity beep only in CP842 pad # 2, not in pin 2 or RP842 both pin 2 and 1

PS: if it's needed I own also a 820-3023 as donor boards for components

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

The measurements do not sound correct. Agree that it may be a "OL" reading.

If you are in resistance mode, short the meter leads and you should read close to '0.00'.

Confirm this and dial up a higher scale setting. Even 100k+ ohms is ok. Then check again.

Post a picture of your meter as well.

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Shorting the probes in resistance mode I got 0.00/0.001 ohms, same thing put probes on ground.

Still got this damn ‘1’ using upper scale

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Try with 20k or 200k scale.

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Already done, it's the same

now I got on pin 1 CP842 = 1.880 ohms then get solid '1' (2k mode), no reads with 20k or 200k scale.

testing RP851 and RP850 i've got solid 1.920 ohms

RP842 still being '1' both pads

Checking the camera part when I removed damaged parts I noticed also this other two components who seems to have sings of burnt, I attached Photos

[mon2]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Leave the IC (first picture) alone. It is ok to me. But the cap does not look great. Make a note of this location and remove this part. Check if the readings change.

[slimmy182]

Re: A2337 new M1 MacBook Air problem Logic Board related, no video backlight 820-0201

Unfortunately, no changes.. it's discouraging