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Working screen module with A2 number stays black on newer FP2

I am surprised that a working screen module with an A2 number does not work with an up-to-date FP2 that runs an A4 screen just fine. When the phone is switched on, the screen stays black.

Does anyone have any information about this?

Presumably you have a second older FP2 from which this screen module is sourced or maybe not? What firmware version is that other FP2 running if this is the case? If it wasn’t for the loss of data issue I would always try re-flashing device firmware so that it has chance to recognise screen upon initial boot up. I remember from years back that you couldn’t change screen upon Nokia 5800XM without re-flashing firmware.

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Please check the software version in Settings > About the phone > scroll down to Build Number.

Does any of the two include a manufacturing date as shown in https://support.fairphone.com/hc/en-us/articles/209635123-Where-to-find-the-unique-identifiers-serial-numbers-of-the-Fairphone-2-modules- ? A date before summer 2017 would indicate the old screen model.

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Correct, I own a second (older) FP2 that currently works with an A4 screen module.

It should be a two weeks old Lineage OS ROM.

Is there any procedure I can follow without changing the screen module from A2 to A4? There is no important data on the phone, so I would give it a try.

It says “Made on 06.01.2016”, and the module S/N is A26AT10848.

I have read about A1 and A4 screen modules, but how does an A2 one differ from the others?

I don’t know what an A1, A2 or A4 screen module is. I know that the model was changed in 2017, but don’t know what serial numbers belong to which model. The “A2” one you are referring too must be an old model if it was produced in 2016. (I believe that the new ones don’t even have a production date printed on them anymore.)

The old screens work with any software version, so I suspect that somehow the screen and core module didn’t make contact.

The A2 screen module works fine with the other core module, but not the other way around, I have checked it. The A4 one works with both cores…

I still don’t know whether this “A4” module is a new or an old one. Does it have a production date on it?

No production date on the A4 one.

Here is a well-done comparison between A1 and A4:

I have a feeling that I got an FP2 from the latest batch, which maybe is no longer compatible to older (non-A4) screen modules…

I have seen that comparison indeed. It is not documented there which serial number was the first new one, hence I wanted to make sure that A4 actually means it’s the new screen.

The core module has not changed, so there is no difference between batches in that regard. I suspect either a contact problem or a bug in the latest LineageOS (although such a bug would probably already have appeared in any of the threads about LineageOS.)

What OS does your other core module run?

Lineage OS, too, the latest version of it.

FYI, I have seen a review with photos of an A3 module that seems to be equal to the latest A4 variant.

I would like to believe you, really. Maybe someone else is able to swap old and new display modules with a lately produced core, and report back. I want to have a working backup phone in case my daily driver has an issue again…

Do both core modules have the same version of modem.zip?

Yes, version 4437.1-FP2-0-08.

That’s indeed the latest baseband version.

Did you already try to take the screen off and put it on again and to clean the connectors to rule out any contact issues?

Yes, I carefully cleaned all connectors to rule out a contact issue.

I have to correct myself: According to the photos in the review, the A3 variant does not equal the A4 one.

Is there a chance to meet anyone from the Austrian Fairphoners in Vienna?

I don’t understand why you keep stressing the A1/A2/A3/A4 variants of screens. From a software point of view there are only two screen types because the panel manufacturer changed once, from JDI to Samsung.

If it’s not the contacts, then you’re probably hitting an LOS software problem. I recall that there was a similar situation on the Düsseldorf Fairphoners meeting last year, where one screen would not work with one specific LineageOS phone for unclear reasons. I think, we need the expertise of @z3ntu here - tagging him so he’ll see the topic.

The Austrian fairphoners would certainly be able to help out - feel free to send them an e-mail at vienna@fairphone.community to arrange a meet in-person.

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Because I have made the experience that an A4 screen works on both cores, but the A2 one does not.

Both cores have Lineage OS 17.1 installed, and there have not been any FP2 display related modifications in the past weeks, so I think this can be ruled out.

Will do, thanks a lot so far for your assistance.