Question about Cobra 148 GTL 120-Channels Base CB Radio
Radio has had no mods. all works well on receive. With another radio on the bench the failing radio can be heard but just has no power to the signal on am or ssb. tx light does go to red when the mike is keyed and the audio is there but there is just no power out
If your receive is good and when you key the mic the meter goes to zero...im almost possitive your final is bad. Try it on side band usb/lsb if it transmitts good its the am final or driver.
Posted on Mar 08, 2015
Posted on Nov 04, 2013
SOURCE: cobra 148 gtl
First take a jumper wire and connect it to the DC Ground of the input of the radio then touch it to the TX pin on the radio if it does keyes up then its in the mic or mic cord on the end of the mic plug or where it goes into the mic cable goes up inside the mic. If the radio don't key up at all then check the main voltage regulator chip one pin will have 8 volts transmit and another pin will have 8volts recieve. If you get no switching DC voltage on the regulator then its bad and needs replacing there is also a known bad capacitor in the radio thats only 10 volts change it to 25 volts at the same capacitance.
Posted on Jan 08, 2008
Your problem is a faulty changeover relay on the circuit board. It is a small black device , and may have the brand name MRATA
etched on it (the switchover contact points are stuck together)
WORTH A TRY GOOD LUCK
Posted on Jun 22, 2008
No audio out / low audio out....This is a constant problem with the COBRA 148 gtl....to get a good level of volume replace the
electro caps ...start around the two speaker wires and work back from there. I'm in the process of rebuilding a 148 gtl and have found caps that are leaky and dried out...after replacing nine the volume went up to a good level...now i need to fix the distortion
and background hash. Did you know that there are many posts
on FIXYA about this same problem I.E. great TX , great PA but poor , or no audio out. these sets have been made in sevetal countries...The sets made in Taiwan or China have poor quality
front panel pots (the carbon track is micro thin and simply wares through to the material the track is printed on) This has the same effect as removing a wire from a pot I.E. no audio. The good news is that 99% of parts in the radio are freely available and that includes the front panel controls. ONE WONDERS IF THE SET IS WORTH THE EFFORT !!!
CHEERS GUYS / GIRLS.
Posted on Jul 03, 2008
bit late, but for anyone else searchng for similar issues, test AM regulator ******, 2SA1012 - replace with good PNP, like TIP42c
Posted on Oct 04, 2012
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