Had an in issue with aerial on my X300 recently where it would go up and down randomly or not at all while driving. Finally got to it and a number of hours of head scratching later I've found two issues.

First was aerial motor wire that was pretty much hanging for its life and came off as soon as I touched it. This was evident when I supplied 12V from the car battery to the green wire going into aerial. This is a switched 12V feed normally coming from the radio and with 12V on it and with the second red wire being always hot, mast should go up but in this case it didn't. Got that fixed but there was still nothing on green wire coming from the radio when it was on.



Then I looked into the radio. One of the wires coming out of the back of it is called P.INT and its the green wire going directly to aerial. This should provide 12V when radio is on. Looking at the trace from the back of the open radio, with the tape drive removed, this was going straight to small power transistor B1240, marked as Q822. Transistor itself turned out to be ok(but can always be a main point of failure with this issue) but the tiny resistor just behind it(marked as 222) wasn't, it was basically no longer soldered in on one side so a quick touch with a hot soldering iron restored 12V on the P.INT wire coming to aerial and all was fixed.



Hopefully this should help someone out there with the same issue!