Słomkowski's technical musings

Playing with software, hardware and touching the sky with a paraglider.

Constant 3.3 V power supply on Baofeng UV-5R/UV-5X microphone connector mod

Easy hack for Baofeng UV-5R/UV-5X, which replaces dual-PTT functionality with constant 3.3 V on 3.5 mm jack tip. Useful for microphones, which require additional power.

My my paramotor helmet requires 3.3 to 5 V power supply for its microphone amplifier. Theoretically, Baofeng UV-5R’s connector is compatible with Kenwood’s, as shown in the schematic:

Kenwood/Baofeng/Wouxun 3.5 mm 2.5 mm jack connector pinout.

In fact, Baofeng UV-5R (circuit board revision VER17) and Baofeng UV-5X do output 3.3 V on their respective 3.5 mm jack tips, but through 10 kΩ resistor. It seems that the tip is used for dual PTT functionality, as shown in the second schematic:

Baofeng 3.5 mm 2.5 mm dual-PTT jack connector pinout.

If you don’t need dual PTT, it is very easy to add constant 3.3 V output. Just add some small value resistor (I used 100 Ω, but 22, 33 or 47 Ω would be better) between pins marked with red circles in the photo. One pin is 3.3 V, the other - tip of the 3.5 mm jack.

Baofeng UV-5R connector modification, which allows constant 3.3 V power supply on 3.5 tip.

You have to disassemble the radio first as shown in this teardown on YouTube. This mod forces 3.3 V on second PTT input, which disables it for good. Baofeng UV-5X has exactly the same circuit board and teardown is exactly the same.