If jumpstarting the battery fails, then the headset might be having more serious issues (ie: the charger circuit being fried) such that one option for fixing the Sony WH-1000XM3 should be to bypass the charging circuit altogether by using a small LiPo USB charging shim.

A micro-USB 5V TP4056 1A charger is used due to its remarkable small size and low cost:

For this task, the right cup will be disassembled, similar to the method for jumpstarting the battery , the micro USB charger will be assembled inside on top of the LiPo batteries and leads will be drawn to connect the micro USB charger in parallel with the Sony WH-1000XM3 charging circuit. Some difficulty lies in the very small PCB contacts on the inside of the cup, as well as finding a direct route from the headphone USB socket to the PCB in order to connect the micro USB charger. Since the micro USB charger used is so small, the micro USB socket on the charger does not need to be desolered and the small PCB will fit right on top of the LiPo battery.

For a first test, the micro USB charger is tested in order to verify that the LiPo battery is charging. In order to do so, the tape is removed from the contacts of the battery and two leads are drawn to the output of the micro USB charger. A 5V load is applied to the input of the charger externally via two wires connected to a voltage generator.

The load used by the micro USB charger is observed to be below which is what the micro USB charger is rated at.

At the output of the micro USB charger, the voltage is checked using a voltmeter while the USB charger is connected to the LiPo battery and observed to be which matches the battery voltage rating of closely.

With all the measurements of the micro USB charger verified, the last step is to probe the headset PCB in order to find a ground lead and a lead, preferably as close to the USB socket as possible in order to avoid any current limiting that might occur due to the circuitry on the PCB.

There are two steps that make the search for the necessary leads easy:

• connect the USB charger to the headphones and the USB end to an USB socket.
• check for continuity between the extreme pins of the USB socket and the PCB - particularly, the solder blobs that are exposed on top of the PCB.

second:

• connect the headphones to an USB charger and check for a voltage differential between any solder contacts previously found on the PCB.

For the Sony WH-1000XM3, in particular, the following solder joints on the PCB seem to be as close as possible to the USB socket - very close to the ribbon cable.

The next hurdle is to connect the two leads to the PCB board right on top of the solder joints which is a difficult task due to the lack of space - a very sharp solder tip is required. Note that the color of the cables leading from the PCB to the micro USB charger do not correspond to the proper polarity. Finally, putting it all together and connecting the USB cable to an USB charger should light up the micro USB charger.

The small black tape is removed and replaced with larger pieces of painter tape in order to hold the wires in place and isolate the contacts.

The cup can now be assembled and everything should fit together perfectly without any resistance.

In the previous section, two solder joints were chosen next to the ribbon cable with the hopes that the points would be as close as possible to the USB connector in order to be able to seep sufficient current for the battery to charge. Unfortunately, that was not the case and the micro USB charger did not manage to charge the battery even after hours of being plugged in. Similarly, in the previous section, the current generator was used to check the power input of the micro USB charger itself but the solder joints on the PCB were not connected in order to check that sufficient Amperes are drawn when the micro USB charger was connected. That being said, the solution was to go further and locate some points on the PCB even closer to the USB connector yet that required a larger intervention than initially was hoped for. It was clear that ideally, the power leads for the micro USB charger should be as close as possible to the USB connector such that finding a way to further disassemble the headset in order to get to the connector was the way forward.

On the other side of the right cup, there is a small plastic rim that is held down using 4 screws and masks the USB connector. Opening the small plastic enclosure reveals a small PCB with the USB connector and plenty of new solder joints to pick from. More than likely, the PCB is a current regulator with the ribbon leading through a small slit to the other side of the PCB. There are about 4 very large, by comparison, exposed solder joints on the small PCB. Using a voltmeter, two of the solder joints are picked and reveal a voltage differential between the two. Connecting two wires to the newly exposed solder joints and then connecting the wires to the micro USB charger whilst checking for the battery level shows that the micro USB charger now manages to properly charge the battery.

However, aside the small slit for the ribbon cable, there is no other way to get to the other side of the headphone cup. In order to do so, a hole has to be drilled into the headphone plastic in order to lead the wires out the other side. Some white painter's tape is used to protect the speaker from any plastic residue that may be displaced when drilling the hole. After many flips of the headphone back and forth, the best place was determined to be next to one of the pillars holding the small plastic rim onto the headset.

Using a Dremel and some very fine tips, a small hole is drilled to the other side in order to connect the wires to the micro USB charger.

The wires are then passed through the newly drilled hole to the other side.

The wires are drawn as close as possible to the battery assembly and will be cut to the correct size.

With the new leads connected to the USB charger, the red LED shines very bright by comparison to the first attempt as an indication that a proper amount of current is now flowing to the micro USB charger.

Some additional painter's tape is added in order to hold the wires in place and the headphones are assembled back together. When the battery charges, the right headphone now tends to get hot, but once the battery is full, the micro USB does its job properly and switches itself off such that the cup on the right headphone starts to cool down meaning that the battery is not being overcharged.

With the charging circuit bypassed, the headphones can now be connected via the USB cable to an USB charger and left to charge. In fact, given that the battery is rated at and that the micro USB charger is rated at as well, with an USB-to-mains adapter, even the "fast charge" functionality is preserved. There is no need to purchase an even more expensive module, and in fact, it would be counter-advised to do so given that the current ratings match up perfectly. After about 10 minutes of charging, the battery was observed to charge from 0% to 50%. Similarly, after a few hours, the Sony headphones report "battery fully charged" when short-pressing the power button with the headphones powered on.

It seems that most likely the fault lies with the actual charging circuitry inside the Sony headphones - perhaps it was damaged upon power cuts when a large current might have burnt the circuit altogether. Nevertheless, instead of tossing the expensive headphones or sending them to "repairs" in order to be told that "there is nothing that can be done" and, more than likely, "a new one has to be bought", this very simple fix will give new life to the headphones. At least, until something else breaks down.