Antenna won't extend, work-around?

[tjblacken]

Mast won't extend, here's what I see...

Motor, gears, clutch, mast and control circuit board all look great.
My '95 S320 has two wires to the antenna... a red/white and a brown.
I can run the motor and antenna either direction with 12V manually. Hooked up, it will retract automatically with 12V supplied by red/white wire. It will not extend though, as no power is coming from the brown wire that connects to the back of the Becker head unit. The brown wire does have continuity.

Is this a fault in the head unit itself? If that's the case, can these old Beckers be repaired?
Can I just send 12V through the brown wire with a switch as a fix? When 12V signal to extend is sent from head unit, is the 12V still present on the red/white wire?

Thanks again
TJ