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

An easy hack for Baofeng UV-5R/UV-5X replaces the dual-PTT functionality with a constant 3.3 V on the 3.5 mm jack tip. This is useful for microphones that require additional power.

My paramotor helmet requires a 3.3 to 5 V power supply for its microphone preamplifier. 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 a constant 3.3 V output. Just add a small value resistor (I used 100 Ω, but 22, 33 or 47 Ω would be better) between the pins marked with red circles in the photo. One pin is 3.3 V, and the other is the 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 video on YouTube. This mod forces 3.3 V on the second PTT input, which disables it permanently. The Baofeng UV-5X has exactly the same circuit board, and the teardown process is the same as well.