Bluetooth Headphone Antenna Problem (1-2 feet of True range)

[zarcanradian]

First, let me be clear about a few points :
1- The problem Lie in the Headphone Bluetooth signal/antenna/chip (100% guarantee it is on the Headphone Bluetooth related side)
2- I VERY MUCH want to repair them, not replace/trash them...
3- It is a chines knockoff of a multi function (Bluetooth Earphones/microphone for call answering or music, Mp3 Player with Micro-SD card slot, Stereo plug entrance to use with Stereo Wire, FM Radio)
4- Sound and function is extremely good, would cost me beyond 200-400$ to get something similar, only have this Bluetooth range related problem

So this pair of headphones that i suspect to have no Bluetooth antenna "wire" integrated as i found absolutely nothing that would be for such a function. I even soldered a wire on the [FM] empty soldering socket hoping i would fix it but it did not effect the result of the Bluetooth in any way (Tested both individually 31mm and 120mm cooper soldered wire, no difference, Bluetooth still fail to work)

To detail the problem, if I'm not wearing the headphones there is barely a couple of feet before it stop working, and if i wear them even at more then 1feet of the Bluetooth device it fail as if my head block the signal (i am not going to use my notebook keyboard as a pillow to make those earphone work...).


Unless the problem lie in the Firmware of the headphone (due to being a chines knockoff, support/updates/download does not exist for it), i suspect all i need is to identify witch soldering point i need to solder the 31mm wire to get the normal Bluetooth range of 30-60 feet...


https://imgur.com/a/i8Qz0cw

 

[Ralston18]

I did some googling using "Bluetooth headphones schematics"

Found many links and some were sites that required a sign up to see more information.

The image area that you flagged as "? BT Antenna ? is likely to be the antenna (trace antenna).

Reference: sixth image in the following link:

https://www.allaboutcircuits.com/news/teardown-tuesday-bluetooth-wireless-headphones/


And do be sure that just adding on an BT antenna wire will actually work.

More reading for you:

https://resources.altium.com/pcb-design-blog/picking-the-right-bluetooth-antenna-for-your-pcb-design

And especially this link:

https://electronics.stackexchange.com/questions/352541/how-does-the-range-of-bluetooth-increases-by-adding-an-antenna

Caveat:

Just providing you with some additional sources of information and in no way recommending that you try such a DIY modification or that any such modification will indeed work.

You are very likely to damage the headphones especially if they are, as you state, " chines [SIC] knockoff of a multi function... etc."

And then everything else you like about them will be lost.

 

[zarcanradian]

After soldering different wires of different lengths, and even removing all antennas did absolutely no change in the range... seem almost like if the Bluetooth antenna function is not actually connected in any parts.
Is any part of the circuit actually "wrong" to prevent Bluetooth antenna connection to the Bluetooth/multi-function chip ? (Black square).
I wish to understand and learn to fix this issue regardless even if i have others headphones.

Also, thanks you for the links and suggestions, although the issue seem to not have been the Antenna in the first place but probably the connection toward the antenna...

 

[Ralston18]

I cannot attest to any part of the circuit being wrong per se.

What I am comfortable about is, for the most part, that many of today's electronic devices and their respective components are not made to be modified or even repaired.

Especially without the exact schematics, tools, and a working environment that supports such attempts.

In fact, attempting any repair or modification is likely to damage the item and/or lose warranty.

Some number of years ago it was fairly easy to open up some device and simply re-solder a problem; e.g., a broken antenna connection.

And schematics were easy to find and obtain although guarded by some companies. Reserved for authorized technicians and repair shops.

You can and should understand the problem - and it does seem that you have done so.

However, a fix may be beyond doing as the PCB is designed and constructed not to be fixable. Not by any average means at least.