In this Instructable, we're diving into an interesting challenge on the healing bench. A friend of mine handed me his MP3 player with a simple complaint: it doesn't work. My initial guess? It might have taken a fall, as shaking it produces some suspicious noises, hinting at a possibly loose wire or a similar issue.

It turned out I was completely wrong, and I went some different paths before I found what was wrong with it.

So, let's jump right in with our tools ready and see what's hiding inside this Bluetooth speaker/player.

Supplies

Tools and materials used in the video:

Hobby Rework Station - https://s.click.aliexpress.com/e/_mNMzK9c
Professional Rework Soldering station - https://s.click.aliexpress.com/e/_Eze4GQ9
USB Connector - https://s.click.aliexpress.com/e/_mKYPzCQ
Multimeter - https://s.click.aliexpress.com/e/_oF0Us5m
Pen Screwdriver - https://s.click.aliexpress.com/e/_ooZj4DO
Wire Snips - https://s.click.aliexpress.com/e/_onMGo9A
Soldering Flux - https://s.click.aliexpress.com/e/_oFAijTQ
Bench Power Supply - https://s.click.aliexpress.com/e/_olvfMc4
USB Power Meter - https://s.click.aliexpress.com/e/_mOJuGDM

By purchasing from the links above, you support me and my channel at no extra cost to you!

Step 1: Disassemble the Speaker

When I started analyzing the speaker, I noticed a noise inside, suggesting a possible loose component. The first step was to examine the bottom of the speaker as I could already see that it had screws exposed. Initially, I tried to remove the speaker by pulling it out, but it was held by the wire so I started to explore the top and its foam cover.

I found some hidden screws under this foram and once I removed them, I was able to get access to the PCB inside and removed it from the enclosure.

This process revealed the battery, which I needed to inspect. At this point, I hadn't spotted any obvious signs of damage, such as water marks or burned components, which is a promising indication that the issue might be repairable.

Step 2: Diagnose the State of the Battery

Moving on to the battery, I fetched my multimeter to check its voltage. Given my experience with electronic repairs, I suspected the battery might be the culprit. In many cases, a battery that is under its minimal voltage can lead to the entire device failing to operate.

Confirming my initial suspicion, the battery didn't show any voltage output when I initially checked it. This was a clear sign that the battery was likely exhausted or damaged. Since I didn't have a replacement battery handy, I decided to improvise by using a salvaged battery, presuming the original one was an 18650 type, which is a common size for such gadgets.

I carefully disassembled the non-functioning battery pack and planned to reuse its protection circuit with the salvaged battery. To ensure accuracy in my troubleshooting, I removed all the stickers and I then rechecked the battery voltage directly. This time, the reading was 2.52 volts. This meant that the battery was empty, but still operational so it should not have prevented the device from operating.

Step 3: Diagnose the Charging Issue

After confirming the battery was OK, I connected a charging lead through my USB power meter. Strangely, there was no current drawing. This was indicative of a potential issue on the PCB, particularly around the charging circuit.

Inspecting the PCB, especially around the charge connector, I noticed something concerning. The tracks leading to the connector seemed lifted from the board, which could create a faulty connection. Applying some pressure to the connector, I could even see it physically lifting from the PCB, confirming my suspicion.

Step 4: Reflow the USB Connector

The next critical step was to address the faulty USB connector. I managed to carefully remove the connector, heating the underside of the board with my hot air station. This is definitely a task that calls for a microscope to accurately see the details on the PCB, but alas, I didn't have one at hand so I had to rely on my eyesight and experience to carry out this delicate operation.

With the connector removed, I cleaned the pads to better understand the situation. It became apparent that both tracks leading to the connector were indeed broken, preventing a proper electrical connection. These tracks needed to be reconnected to the test pad that they went to originally.

To re-solder the USB connector, I applied a bit of fresh solder to the pads and reheated the connector from the bottom, just as I had done to remove it. I also planned to run a thin piece of wire from the test pad to the corresponding pins on the connector, ensuring that conductivity was restored. It was a tricky repair, hindered by the awkward angles and small size of the components, but I managed to do it

Step 5: Test and Reassemble

With the USB connector re-soldered and bridged wires in place, it was time to test the repair. I cautiously reconnected the battery, eager to see if it would accept a charge. Initially, there was no current, but a reassuring blue light soon flickered on, indicating some activity. The battery didn't seem to be drawing much current initially, however, after a quick touch-up job on the pins of the connector, it started charging with around 340 milliamps and showed that it was alive.

This was the confirmation I needed: it was indeed charging. Double-checking the battery voltage showed an increase, a sign that the repair was successful. I decided to leave it charging for a while before reassembly.

After sufficient charging, I cautiously reassembled the Bluetooth speaker, connecting it just enough to ensure its functionality with the speaker. It sprang to life, and I paired it with my phone via Bluetooth. To avoid copyright issues, I demonstrated sound output using one of my own videos. The MP3 player worked perfectly – music to my ears, quite literally.

With the repair accomplished, I would reassemble the entire unit and return it to my friend, fixed and ready for use. This process of troubleshooting, soldering, and patience demonstrates the joys of electronic repair. If any of you have questions or are interested in seeing more repairs and projects, I encourage you to leave comments or subscribe for future updates.