Speaker not working after flex cable replacement

Hi Jxhnny,

Generally, no, the battery isn't likely to be the source of your speaker problem, but any smell coming from it indicates the sealed casing has been compromised and the battery should be replaced immediately. Personally, I would suggest you not use the phone until you replace the battery, but that's up to you.

I'm not sure where you got your instructions for replacing the power/flash/microphone flex assembly, but there's really nothing in it that should have any direct effect on the loudspeaker. Just to be sure, we're talking about the one in the bottom of the phone and not the one used for phone calls (the earpiece speaker), right? Here's a guide that shows the proper procedure for making that repair.

Manuales / Apple iPhone 11 Pro Max / Flex with power button, flash and microphone - Nadie Me Llama Gallina

In cases like this where something unrelated stopped working when you did a repair, it's important you go back through and double-check your work. In this case, the place to look would be the connector that brings the speaker wires to the motherboard. That would be the lightning connector assembly; the speaker plugs into that and that plugs into the motherboard.

Manuales / Apple iPhone 11 Pro Max / Auxiliary board - Nadie Me Llama Gallina

There are two plugs to the motherboard, and there's no information on which one it is, but if I had to guess I'd put my money on the smaller of the two as being the most likely. Those both have to be unplugged in order to remove the motherboard. Here are pictures from that guide.

So the thing to do here is to open the phone back up and unplug both of those connectors. Check them over carefully with a magnifying glass and a bright light looking for any bent or broken pins on both the cable connectors and the motherboard connectors. Bent pins can sometimes be straightened with fine tip tweezers, but broken or missing pins will obviously be more problematic. While you have it unplugged, check as much of the flex cable as you can see for any signs of damage; if you find any on the connector or cable you'll need to replace that assembly.

Anyway, my best guess is that it's probably just a matter of the plug not being inserted fully, so once you're satisfied everything looks okay, reconnect them then plug in the rest of the cables you've disconnected (save the battery for the very last), then power the phone back up and see if anything has changed. Pay special attention to getting the lightning connectors plugged in fully and completely; you should feel something of a click when the pop into place.

Test the speaker and see if it's working now. If so, congratulate yourself on a successful repair and close it back up (hopefully with a new battery now). Otherwise you can try replacing the lightning cable assembly and/or the speaker itself, but feel free to come on back here and let us know what you found and we'll see what we can figure out to get your phone working again.

Good luck and let us know what happens!