OK. On the DX44, using the EPT0SSB50B echo board, there is a blue wire soldered in to the board. I disconnected it, and no difference.
Just a note from here - If I say green, brown, yellow, orange, etc... I am red/green colorblind, so it may even be a shade of green and I call it blue. I ger browns and dark greens mixed up, etc. I added pics for reference.
There is a 2 pin plug, rd and blk wires, they go to the back of the on/off part of the control knob on the radio front. Unplugged that, no audio but it keys up to TX.
a white plug, with 3 pins. Black, Brown (?), and yellow (?) wires. unplug that and no response when keying mic. Black and brown go to board on mick socket. Yellow to main board beside R179. I disconnect the yellow from the plug, wasn't it.
A Brown 3 pin plug with a red, green, yellow wire. They go to a white 3-pin plug on the main board right behind the s-meter.
Otherwise, you have the 2 main "coaxial" wires, each with 3 wires, that go from the board to the control knob. They both have red, green, and shield.