820-01041 16GB-->32GB Upgrade, No Boot.

[ugamazing]

Really stumped with this one and hoping someone can give some insight on what to check next:

1. 820-01041 2.9/16/512 board that we are upgrading the RAM on to 32GB.

2. Replaced 16GB Micron set with 32GB Hynix set and adjusted the RAMCFG strap resistors accordingly. We pulled the 32GB set from an identical board that had 32GB RAM (820-01041 2.9/32/512). We reballed the chips ourselves (twice!) and results were the same.

3. Unit powers fine and draws normal power, but does not chime or boot (and no charge tone when connecting charger).

4. Unit restores fine via DFU in a normal manner; no funkiness like hanging or anything like that. Restores to padlock, but unit doesn't chime or boot.

5. We replaced the original 16GB of RAM (and re-configured the RAMCFG straps) and board worked perfectly. It would boot, chime, install MacOS, restore via DFU, etc., all without issues.

6. We tried a SECOND SET of 32GB RAM (Hynix) pulled from another identical board (01041 2.9/32/512) and the issue is *exactly the same*. So, there's clearly some issue with configuring the board post-install of the RAM chips.

7. We scoured the board and it matches an identical board; CFG resistors all match, but board does not chime or boot.

Is there something obvious that we are missing here? We've upgraded RAM on tons of boards, but this is the first one that's given us an issue. I thought possibly the PCH or CPU had been damaged from heat, but we confirmed that's not the case by reinstalling original 16GB RAM set (and board worked well).

Any ideas where to go next? Thanks in advance for any help.

[dellxps15]

Re: 820-01041 16GB-->32GB Upgrade, No Boot.

what about bios ?

[ugamazing]

Re: 820-01041 16GB-->32GB Upgrade, No Boot.

This is an 820-01041, so T2 handles BIOS and a DFU restore should take care of that. But, I don't think a DFU is actually necessary on RAM upgrades (never had to before, even on T2 boards).

Someone else may know better, though. Thank you for replying!

[piernov]

Re: 820-01041 16GB-->32GB Upgrade, No Boot.

If the BOM option table is correct you need to add 1k resistors at R1530 and R1532 for Hynix 32GB.
R1531, R1533 and R1534 are already populated for Micron 16GB.
That way, RAMCFG[4:0] is all pulled low.
This is what you did, right?

[ugamazing]

Re: 820-01041 16GB-->32GB Upgrade, No Boot.

Thanks, Piernov! Yes, exactly; I even compared to an identical-spec (dead) board to confirm all matches (after following the BOM table). I'm really wondering if there is some other configuration or stuffed components I'm overlooking? I'm going to go over the board again today. But very confident in the soldering, and unless 2 sets of 32GB RAM are faulty, I'm not sure what else it could be. I even replaced the PCH again last night just to be sure, and *exact* same symptoms persist. Something else to note: During the DFU restore, the board/unit (with 32GB upgrade) does not show any video (i.e. apple/loading bar) during the restore, but it does finish successfully every single time.

Other things I tried, just to avoid something simple being the issue: Tried new LCD cable, new/different case assembly, etc. Lost on this one; maybe I should just put back the 16GB and move on, haha!

By the way: Does anyone know if these boards will give the traditional 3-beeps if RAM is bad/damaged? Now that I think of it, I've not ever heard any of the T2 models give a bad-RAM tone, ever.

[anhbanxoi]

Re: 820-01041 16GB-->32GB Upgrade, No Boot.

I'm getting the same symptom as your but in my case it's original motherboard. Can restore in DFU but no boot & chime. Also no video during DFU restore. I need to check the RAM also. Maybe RAM is dead. Thank you for the information.

[ugamazing]

Re: 820-01041 16GB-->32GB Upgrade, No Boot.

I'm getting the same symptom as your but in my case it's original motherboard. Can restore in DFU but no boot & chime. Also no video during DFU restore. I need to check the RAM also. Maybe RAM is dead. Thank you for the information.

I've thought the same, as we have a dozen or so boards with similar symptoms (restore fine, no video/etc). I've chalked most up to dead CPU, or possibly nand issues. I have replaced the T2 on one of them (with known-good chip), and issue persisted. Appears that a board can complete DFU restore fine with both a faulty CPU/eGPU (not shorted) and faulty RAM, which would make sense, given T2 is a dual-layer SOC with both a CPU and RAM.

But I'm not sure if these boards give any indication of bad RAM. I don't think they do, but can let someone else chime in.