[Home Appliance Repair Record 7] Wireless Headset

This time, I am repairing a home appliance.

The item requested for repair this time

When I write an article about a stabilized power supply, I keep getting requests to repair stabilized power supplies, and when I write about wireless earphones, I keep getting requests for similar headphones with microphone functions. I cannot deny that it lacks variety, but this time it is a headset with a microphone function (Jabra Evolve2 75).

Embarrassingly, I did not know about Jabra, and when I first received the request, I thought, "Wouldn't it be cheaper to just buy a new headset?" However, this headset was a very high-performance item that costs around 40,000 yen.
Well, if it can be fixed, you would want to fix it, right?

By the way, Jabra is a Danish company, and they seem to have a good reputation for features like noise cancellation.

Symptoms

It is similar to previous repair items, but the symptom is that only the microphone function does not work, while everything else is normal.
Moreover, the microphone has a structure that allows it to be stowed away, and since the voice guidance plays normally when it is stowed, it seems that the microphone function is not completely broken. It is simply a symptom where it cannot pick up voice as a microphone.

Start of disassembly

Home Appliance Repair 6 Unlike the bone conduction earphones, there are screws, but they are special screws and cannot be easily disassembled. Is this due to the requirements of Japan's Radio Law?

Long before I started Note, I repaired a Nintendo Switch controller that I use at home, and at that time, I bought a full set of bits (tips) for every possible special screw, so I broke through the special screws without any difficulty lol

It is a circuit board that truly feels like a high-end headphone.
The microphone that is the issue this time was the type that can be stowed by flipping it up with a common hinge. There is a magnet on the opposite side of the microphone (inside the case), and a sensor that detects that magnetic force was used to detect the raising and lowering of the microphone.
Since this is a mechanism that is not directly related to the function of picking up microphone sound, I think this part is working without any problems.

Since only the function of picking up microphone sound is broken, it is highly likely that it is either the microphone element or the wiring.
In terms of probability, I think it is highly likely that the FPC (Flexible Printed Circuits) is broken, but as far as I can see visually, there was no break near the place where the most stress is applied.
However, when I move only the part suspected of being broken a little, noise enters, so I think it is broken, but I cannot quite confirm it.

In that case, I need to start searching for the cause in earnest, but the microphone element is housed inside the arm with a cool design in a structure that cannot be disassembled.
When I confirmed with the client whether it was okay to disassemble it even if it meant scratching the tip of the microphone arm, or whether to prioritize the design and give up on repairing the microphone function, the answer was that it was okay to disassemble it.

Further disassembly

When I disassembled it and looked at the circuit board, there were two microphone elements inside the tip of the microphone arm. Since I cannot find the corresponding part even if I search by the part number engraved on the element, it seems to be a Jabra-exclusive part.
I do not understand why there are two elements, but when I checked with an oscilloscope, 1.8V was supplied as power, and the clock and audio signals common to digital microphone elements were wired respectively. By the way, there is a small switch on this microphone arm.

A total of 5 wires, including the positive power supply (1.8V), GND, switch signal line, microphone clock line, and microphone signal line, are routed via FPC.When I checked the continuity of these 5 wires at both ends of the FPC (the board at the tip of the microphone and the board of the headphones), the microphone signal line was about to break.

Coincidentally, power and a clock are supplied to the microphone, and it is in an operable state. If a microphone signal is output on the board side at the tip of the microphone, it can be judged that there is no failure in the microphone.
As a result, a PWM-like random signal was confirmed, and I judged that it was not a failure of the microphone element itself.

Repair started

In that case, it means I just need to fix the break in the FPC, but replacing the FPC is the standard procedure when it breaks. I don't think repairing it with solder is a very common repair method. According to the client and the manufacturer's website, Jabra has already stopped accepting repairs for this model number (though it looks like you can buy a new one from the manufacturer's website...).
Since obtaining replacement parts is not an option, I decided to repair it with solder.

For the three wires other than power and GND, both the conductive parts and the spacing between adjacent lines are 0.1mm. I had considered the possibility of giving up on the FPC and replacing all five wires with bypasses, so I had prepared polyurethane-coated enameled wire, but the wire I prepared was 0.24mm in diameter. It couldn't be used for reinforcement, so I managed to secure 0.1mm copper wire by unraveling some appropriate stranded wire.

Fortunately, this FPC has a polyimide coating that doesn't melt with the heat of a soldering iron. I carefully scraped the surface and was able to solder it by connecting it with the 0.1mm wire. If left as is, there is a high possibility that it would break again, so I coated it with UV-curable resin and the repair was complete.

Although I was able to ensure conductivity, a problem occurred here. I have to pass this FPC back through the arm, but it couldn't be pushed through due to the stiffness of the FPC...
After thinking about it, I decided to cut a transparent lid from a bento or hors d'oeuvre container (probably PET resin) that you can buy at a supermarket, etc., to the same width as the FPC and use it as a guide. It had just the right amount of elasticity and stiffness, making it perfect as a guide. I put everything back to normal, and with this, the repair is truly complete.

When I checked the operation, there were times when it picked up sound and times when it didn't, depending on the Bluetooth settings, but I decided to have the client check it in their own environment and returned it.

This time, there were no parts replacement costs, so my out-of-pocket expenses were zero (the client paid for the round-trip shipping).

Finally

I dealt with it using the rough method of repairing the FPC break with solder.
I was saved because the broken part of the FPC I repaired happened to be in an environment where it wasn't subjected to much stress, but I don't think it would have been possible if it were in a part that was completely subjected to stress. I would like to consider other FPC break repair methods.

Even so, the headphones this time were designed at a real cost, and I disassembled them while thinking, 'Wow.'
However, the latest electronic devices have small parts that have no markings, or even if they do, they only have identification codes, so there are many parts with unknown manufacturers and unknown model numbers.
I was once again painfully reminded that this is a repairman's nightmare lol

***

Thank you for reading to the end!
I would appreciate it if you could leave a comment.

I do appliance repairs to combine hobby and profit. For now, I'm still in training, so I'll handle it for free.I am looking for things you want me to repairYou can find the status of past repairs here.
If possible, please send me something different from what I've done before (lol)

1st: Stabilized Power Supply
2nd: Stabilized Power Supply
3rd: Stabilized Power Supply
4th: Remote Control
5th: Digital Delay System
6th: Bone Conduction Wireless Earphones

Please apply via the email listed on the website below, the 'Contact Creator' section on NOTE, or X (formerly twitter) @rilp1eYxYyIeYCZ.