Looking around online, it seems this unit breaks a lot. Mostly the cause of the breakage seems to be the USB charging port on the back. It seems to wear out and bend/snap, making it impossible to charge the unit.
Replacing the USB port isn’t too tricky if you’re moderately competent with a soldering iron. Here’s the steps:
Disassemble the Monitor
The part with the purple surround on the front of the monitor is just a glued on screen cover. It’s only glued around the edge – not to the screen itself. Heat it up a bit with a hair dryer or heat gun to loosen the glue and gently pry it up away from the screen. This will reveal 4 screws:
Remove the 4 screws and you can now gently pry between the purple band and the back of the unit to remove the back cover:
Unplug the speaker to fully remove the rear cover:
You can now remove the 4 internal screws which secure the purple plastic surround and then lift out the board. You can see on this one that the USB port is bent – the inside is also snapped:
Carefully desolder the USB port from the board. There’s 7 points of connection – the 5 pins of the port and two securing pins at either side. I started by heating the solder of the securing pins whilst pulling gently at the metal part of the port. Once the metal was off, I individually desoldered each of the 5 pins – pull a pin up with pliers and heat up its solder.
Once all the pins were out and the plastic bit was removed, you can clean the solder out of the holes with a soldering iron and solder sucker:
Now you need to find a replacement Micro USB Port. Here’s what it needs to look like:
Here’s the datasheet of the one pictured: 614105150721. Note the dimensions – you need to make sure the height is pretty close to the original (7.1mm).
You can get them for 10 a penny on AliExpress, eBay, etc. but they’ll come from China and will take a while. At time of writing, Farnell sold the right part but once you add shipping et al. it’s not cheap.
EDIT: As some comments have said, you can get them on eBay specifically listed for the BT 5000/6000 monitor.
Once you have the connector, just solder it on in the right place. Here’s how it looks, before soldering, under a microscope:
The large outer pins are just to keep the port stuck to the board securely. The key pins to solder, for charging, are the ones with the larger PCB traces on the left and right of the set of 5 pins. These are 5v and GND. The 3 middle pins are data pins so only strictly required if you want to connect the monitor to a computer and upgrade it, or something (I’ve never tried this). Either way, try to solder all 7 pins securely, if you can. I used a very fine (0.3mm) solder and put a bit of flux on the board before soldering.
Once you’re done, put the monitor back together and it should charge as expected: