AirPods Max: No Power on Battery, Reset Fails, No Continuity Through Headband

Hello,

I’m having a very unusual issue with my AirPods Max and I’m trying to determine whether the problem is coming from the headband/interconnect or from another internal component.

Background

This issue started after the AirPods Max had been left outside of their Smart Case for several weeks, during which time the battery became completely discharged.

After that long period, I charged them again.

At first, after many, many attempts, I managed to get them to connect to my iPhone.

However, even when they appeared connected, I was unable to switch the audio output to the AirPods Max on my iPhone.

I managed to get them connected like this only twice.

After that, I was never able to connect them again, and eventually they stopped showing any normal sign of life at all.

Symptoms

The headphones show absolutely no sign of life when disconnected from external power.

However, when connected to a charger:

• the status LED works;
• the battery appears to charge normally;
• the LED goes from orange to green as the battery charges.

As soon as I disconnect the charging cable:

• no LED;
• no response from any button;
• the headphones appear completely dead.

Reset does not complete

I have tried Apple’s restart/factory reset procedure using the Digital Crown and Noise Control button.

Even while connected to power, the reset does not complete.

When the headphones are connected to external power, I get the flashing orange/amber LED during the reset procedure, but it never transitions to flashing white, even if I continue holding both buttons.

When the charging cable is disconnected, the headphones show absolutely no LED activity at all and do not respond to the reset procedure.

What I have already checked

So far I have:

• replaced the battery;
• visually inspected the internal boards;
• confirmed there is no visible corrosion, liquid damage, or damaged component;
• cleaned the headband contacts;
• cleaned the hinge contacts/connectors;
• checked and reseated the internal connectors.

Replacing the battery made no difference.

Headband continuity test

I removed the headband and performed continuity tests between the electrical contacts at both ends.

I tested every possible combination of contacts between the two ends, but I cannot find continuity through the headband at all.

I also tested the system with the hinges connected and measured between the corresponding internal connectors that lead toward the boards on each ear cup.

Again, I could not find continuity from one side to the other.

This makes me suspect that there may be an internal break somewhere inside the headband/interconnect assembly.

My questions

Does anyone know:

• what the expected pin-to-pin mapping or resistance values are;
• whether an internally broken headband/interconnect could cause these exact symptoms:
  • LED/activity only while connected to external power;
  • battery appears to charge normally;
  • absolutely no response when unplugged;
  • reset starts with the amber/orange flashing LED but never reaches the flashing white stage;
  • temporary Bluetooth connection after many attempts, but no ability to route audio to the AirPods Max.

The part that confuses me the most is that after recharging them from a completely dead state, they did briefly connect to my iPhone twice, but audio output could never actually be switched to the AirPods Max.

After that, they never connected again.

Thanks!