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

[slimmy182]

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

Yes, RP842 is only a 0 ohm resistor. So you can remove it and apply a blob of solder to act like a short circuit.

I've shorted the two pin, and now with LCD connected to the board I have 1.80v in RP842 in both side, but I guess the switching power IC (UP800) is not ENABLED as backlight still don't work.

It can depends on missing components I removed in the CAMERA circuit?

[mon2]

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

Do place the filter back on for the camera to complete the circuit. A filter is to clean up the voltage rail but for this testing, you can use a solder blob.

At this time, believe that your backlight IC should be replaced. The upstream enable signal is present and is trying to enable the IC but the IC is not performing its BOOST function to offer the 25V++ for the backlight signal.

[slimmy182]

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

Actually I miss also LP670. Do you know where I can find this backlight IC ?

[mon2]

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

1) LP670 - is available from Arrow / Digikey / Mouser Electronics.

(update link for Arrow for a suitable part @ LP670):

https://www.arrow.com/en/products/bl...-manufacturing


Do you or someone you know have a VAT # ? If yes, then it should be possible to drop ship these to you from Arrow.com. Without a VAT #, unable to ship these to you from Arrow.

2) The backlight IC is available from Aliexpress:

LP8548B1SQ-04

https://www.aliexpress.com/item/3285...rch-mainSearch

* this is a store we have used in the past with good ratings
* recommend to pick up at least 2 of these parts as they are not available through mainstream distribution

NB: Just checked and apparently Ebay (Napoli) has some seller who is carrying this part as well - found through Google


3) Are you comfortable with the replacement of this QFN packaged IC ? If not, recommend to work with a local repair shop of cellphones or similar. Should only take 15-30 mins (max) to replace this IC.

Need kapton tape to protect the surrounding parts so they do not fly away. Flux the site and hot air tool to remove and replace. Tweezers to remove / apply the parts.

[slimmy182]

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

Thank you very much for all the advice and walkthrough explanations. I’ve just ordered this IC backlight. I’ll let you know when arrives.

Anyway, do you exclude short to ground in one of the capacitor chain? This MacBook has dropped, they could be “cracked” inside?

[mon2]

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

If you suspect a capacitor to be shorted to ground, check the resistance on that rail.

Remove all power anytime you are measuring the resistance of a component.

Red meter lead on one capacitor pin; Black meter lead to ground.

If the RED lead is on the ground side of the capacitor then expect ~0 ohms since this will be direct connection to the black meter lead which is also ground potential.

A shorted cap will show very low resistance but low voltage rails are often with low resistance, by design. Best to measure and post any such locations for a deeper review.

Do look for off color caps / caps with cracks, etc. that may indicate a damaged component. If you are suspecting such a defect, hot air off the part and then check the resistance again for that cluster of caps.

[slimmy182]

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

Hello. I've replaced components on camera circuita and now it is perfectly working as expected.

I've replaced also the IC backlight, but unfortunately still no backlight.

When IC was off the board I checked the continuity in the pads looking for short, I've reported what I found on the attached image. I put red color on the pads that show me 0.00 ohms resistance, all the other was 'OL'

PS: now CP860 cluster caps show solid 0.00 ohms resistance. Do you think my be worth change also other surrounding of prevosuly damaged components of the camera circuit?

[mon2]

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

1) The red marked pads that are showing 0 ohms to ground are correct. Each is a ground connection to the underside metal belly pad (heatsink pad). No fault here.

2) To debug the short on the bulk caps for this boost power rail, use the hot air to lift up one leg of diode D800 (see attached on the location).

Once you have lifted up this one side (either side of the diode is ok), do not apply power to the logic board but check the resistance to ground once again for the bulk caps. Do not connect a LCD panel during these tests.

We need to be sure the fault is not in the LCD panel so it will remain disconnected.

With this procedure, the shorted component is narrowed down to this cluster of caps.

Post the resistance for the same cap cluster with the diode out of circuit.

[slimmy182]

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

Look what I've found! Cap removed, short gone. It was not craked before today, maybe multiple heating give this last breath

it's a 2.2uf 10% 100v capacitor right? Unfortunately my donor board does not have one.

The backlight screen works installed in other machine, so it's not bad for sure

[mon2]

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

That looks like the bad actor on the board. Remove it and check the resistance again. Biting my nails in anticipation of some good news. We could all use it by now

[slimmy182]

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

resistance to ground CP860 = 168.5 ohms (200K scale).

[mon2]

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

That is ok since you are in the 200k scale so the reading is actually 168.5Kohms = 168,500 ohms. Much much better than the 0 ohms from before.

Be sure of this value - check it a few times. Then place back the diode if it was removed.

Then check the resistance again to be sure it is a high resistance.

Then attach the LCD (no power!!!) - check the resistance again on this cap cluster.

Finally, power up to check the results of the backlight operation.

[slimmy182]

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

Thank you so much for helping me, really. Measured resistance again, it's the same.

Actually I don't have this CAP, I need to order it and wait for delivery before turning on and check

[mon2]

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

No. Not needed. You can test without it for now. Long term, yes but it is not a show stopper.

[slimmy182]

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

DC IN, CP860 = 45V

and then, finally.. WE HAVE BACKLIGHT! Camera and video output is working too.

This was my really first time attempt to repair a logic board. I'm really happy and proud of my self. I learned a lot and enjoyed it

But the most important feeling I have is that I'm very, very grateful for your help that make all seems so easy to do. Thank you mon2

I hope this walkthrough could help someone, this community is amazing and deserve to grow.

my 2 cents: A2179 and A2337 backlight only (not whole display or LCD, so basically only frame + backlight, ) are interchangeable

[abinformatica]

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

Hi, I have the same problem.
I was following all the directions given step by step and I have the exact same measurements.

Unfortunately the topic got stuck and I don't know if and how it was resolved.

Unfortunately the topic got stuck and I don't know if and how it was resolved.

Continuing with these measurements, what else can I measure?

Thanks

[mon2]

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

Meter in dc volts mode (20v or higher scale is ok).

Carefully, measure the voltage to ground of each side of the fuse at FP800.

Red meter probe to fuse. Black meter probe to ground.

Post the measurements. Just checking that the fuse is not blown. If in doubt of the fuse location, post pics. It should be a white body component which is common to fuses.

[chxrock]

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

Sorry for my bad english, I have the same problem. I have the 45V for Backlight but no image. can someone help me?

[mon2]

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

1) toggle the caps key - does the led toggle? This is to confirm the logic board is booted.

2) test with an external monitor using a type c video dongle

3) review this webpage:

https://logi.wiki/index.php/Backlight_Troubleshooting

With 45v, the voltage is too high for the backlight voltage. A load is not seen by this power rail. Check your cables. Check for liquid damage. Inspect and clean contacts linked to the video and backlight if they appear to be dirty. Use ipa (alcohol) and cotton swabs.