How to do Bluetooth switch mod on ZK-TB21/ZK-1002T?

[lene]

Hi there!

I have those amps and I like them, except for the fact that Bluetooth is available for pairing when AUX input is connected. I read that they can be flashed but this is most likely not possible (easy) with those boards and I see that it's not easy to get datasheets for the BT chip.

So: Where do you think I can make a mod to add a switch? Adding photos of the board, one is a close-up.

Edit: By a switch I mean where I can cut. I see the following options:

• Find out where to cut and add wires for an external switch
• Disable BT by placing the amp in a Faraday cage
• Disable BT in the antenna connection:
  • Doesn't work for a switch because I would change the antenna design
  • Might fry something if I cut it because of RF power not going anywhere (not sure)

Suggestions welcome.

Thanks.

 

[linhtinh]

I don't quite understand your intention, I guess you want to turn off bluetooth with a switch? If so then find the power supply pins of the ic, cut the circuit line off & connect to the switch.

 

[lene]

I can try probing because I couldn't find a datasheet... There might be more than one connection to V+. I also wonder if the chip manages the AUX/BT switching.

OTOH I commented about the issue in a YouTube review for the ZK-TB21 and got this answer:

Yes that's common with the jieli microcontrollers on them, they can be flashed with firmware that gives aux priority over Bluetooth so you can't connect to it when aux is connected. I so far have not found any way to do this though. There are some forum threads online that discuss it but don't have any success.

 

[Tenjin Tetsujin]

Did you find anything about this? I stumbled upon this on Reddit looking for the jl Bluetooth pin out diagram and the model numbers you just take the first two letters, ad 69 and then add the last numbers and letters at the end

 

[lene]

Hi there. I did cut the antenna and grounded the pin as I read somewhere and Bluetooth was still working. I gave up... BTW, the one I have now is from Fosi Audio and it's no longer in production. It has less gain than the others I had and I think it sounds nice.