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Frank Gilliland · September 9th 06, 11:51 AM posted to rec.radio.cb

On 8 Sep 2006 09:39:07 -0700, wrote in
.com:

I have a Cobra 148GTL AM/SSB citizen's band radio that appears to be
fairly old (made in Taiwan) and has the following problems:

(1) Despite what LED channel indicator shows, the receiver doesn't
change frequency.

(2) When I push the mic push-to-talk button, no signal is transmitted
and the receive/transmit (RX/TX) light remains green (receive mode).

(3) When I first got the rig, it did transmit and change receive
channels, but on frequencies above the CB band.

I suspect the problem is in the frequency synthesis phase-locked loop
or related circuitry. Did a capacitor failed after being uncharged for
years?

Who knows. The radio has been "tweaked" by someone who clearly didn't
know what they were doing. The problem could be just a cold solder
joint, the core in the oscillator coil could be cracked, your PLL chip
could be fried..... it's a big list of possibilities.

I thought I'd ask newsgroup readers for any insight before I charge in
with my oscilloscope and soldering iron. Perhaps some of you
encountered similar problems with this unit and can suggest a good
starting point diagnosis and repair.

You can either spend time time and effort to restore and de-mod the
radio, or take the more practical route and just buy a new one.