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Problems with Cobra 148GTL CB radio

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September 8th 06, 06:43 PM posted to rec.radio.cb

Telstar Electronics Telstar Electronics is offline

Telstar Electronics is offline

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Problems with Cobra 148GTL CB radio

wrote:
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?

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.

-Dave

The first thing that I would check would be your B-supplies. They have
an IC that supplies seperate DC sources for receive and transmit. Some
of your issues seem may point to one of those sources being dead. As
for your capacitor comment... electrolytic capacitors these days (and
even in the recent past) have an electrolyte and containment design
that is very reliable. Don't spend too much time thinking along those
lines. Hope that helps...

www.telstar-electronics.com

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