View Full Version : Uniden PC78LTW Issue

06-28-2015, 08:45 PM
Uniden PC78LTW. Transmits fine, but has a delay in keying up and actually transmitting, occasionally doesn't transmit at all. I did notice the ground connection on the inside of the SO-239 connector had broken loose from its resistor, so I soldered that back into place because I noticed that sometimes it would fail to transmit unless you wiggled the SO-239. I also removed the old solder and re-soldered the center conductor for the SO-239 and checked continuity with an ohm-meter to ensure that there wasn't a cold solder joint or something. It now transmits just fine without wiggling, but still very weak on receiving other stations, and sometimes won't transmit until it's been left on for a few minutes. On the receiving end when you key it up it sounds like it farts for a second before it clears up and sounds fine. It has no receive at all except white noise when an antenna is connected, but cannot hear radios that I know are transmitting good (I kept a scanner tuned to the freq to make sure everything was working fine). Even tried separating radios by about 1 mile to make sure I just wasn't too close. Most of the time it will transmit just fine but still has no receive, even with the popping/farting sound on key up. We've swapped hand mics, power cords/sources, antennas, even put one of my radios on all of his gear, which he's using in the interim, and it works just fine, so the issue is indeed something with this radio.

The radio was undervolted recently. It was in my brother's car when his alternator went bad and the car died when his battery dipped too low to fire the spark plugs. I don't know exactly how low the voltage got and for how long, but the radio was definitely undervolted for at least several minutes before I got to him to tow him home.


06-28-2015, 08:59 PM
Found the problem not 2 minutes after I posted this; dirty channel selector.

06-28-2015, 09:51 PM
Scratch that, that was one of many issues. Now trying to track down a cold solder joint. Radio receives fine above channel 30 or so, intermittent below that.