Question about Cobra 148 GTL 120-Channels Base CB Radio

2 Answers

Cobra 148GTL Missing TX Modulation

I have a Cobra 148GTL. TX light changes and carrier is present but there is no modulation. Checked microphone appears to be working. Replaced Capacitor C176 with a 16v 47uF identical capacitor (in the audio amp stage). Problem affects both SSB and AM. Receive works great. Carrier activates other radio just can't here voice.

Posted by Anonymous on

  • Anonymous Jul 15, 2008

    Hooked this up to a watt meter, no SSB out put wattage.

  • Mark Oct 04, 2012

    possible dead 2sa1012 AM regulator. check & replace with good PNP. TIP42c seems ok

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2 Answers

Check voltage regulator

Posted on Sep 15, 2008

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The problem is most likely the audio ic . open the radio and see if the diode 44 is blown or see if you see anything that looks like it got hot around the plug area. if not contact me and i will buy it. is it an old or new 148 gtl.Read more

Posted on Dec 06, 2008

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1 Answer

Good day I have an cobra 148 Gtl tx and rx a working but no out put


It might not seem obvious but on many, if not all, current CB radios have separate wires coming from the microphone for RX and TX. It seems like the mic wire for TRANSMIT may be open. It is a common failure.

Feb 28, 2015 | Cobra 148GTL

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Looking for the best micaphone for cobra 148gtl


Turner+2 Ham CB Radio Microphone Transistorized SSB Base Station Shark Fin

turner microphone ' eBay

Jul 29, 2012 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

My Cobra 29 LX receives including the weather but can't transmit


If the relay contacts are closing. You may have blown the output transistor, however a broken wire in the microphone can also create the symptoms you describe. .

you can check by using a #47 light bulb soldered to a PL259 connector as a dummy load. If it lights, the carrier is present, but you may not have voice modulation which will show as differences in light intensity as you speak. If no modulation, the microphone is the first thing to look at.

The relay contacts may also be very pitted or corroded and not achieving continuity.

Feb 17, 2012 | Cobra 29 LTD CB Radio

2 Answers

I have a Older 148GTL, when I key down the mike for tx on AM, the red tx lite goes on and the needle pegs, No Modulation is heard on friends radios, appears to work normal on SSB


Hi, my name is John. Welcome to Fixya. Try turning your MIC GAIN to MAX and see what happens. Let me know how it goes, may have further. Thanks for choosing Fixya.....John

Oct 26, 2010 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

I have a Cobra 18 wx st. I am not able to transmit anything on it. I have checked the antenna cables and and all external connections. I receive all the wb just fine but the CB gives me nothing. I tried a...


That's usually a defective amc stage that produces RX audio and TX modulation. It's an integrated circuit that will require a tech fixing it. You will have a transmitted carrier with no modulation, and no sound in your speaker. However, make sure you have a good mike plugged in first, and substitute a known good mike to verify it's not the mike. With the WX band working, the above may not apply.

See if you have a carrier...signal going out, but no modulation. Get your Tech to check the mike wiring/circuitry inside the radio, also.

Jul 06, 2010 | Cobra 18 WX ST 40-Channels Base CB Radio

1 Answer

I have a cobra 148gtl that has 26 meg and high


VR10,,tuneL37,L38 you can remove TR24 it's for
modulation,but it may over modulat if removed.
that will get you started.

Aug 27, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Cobra 148GTL can't TX on USB


Its the cap that feeds the first transistor to the first of the finals. It is either shorted or burned out.

Or the audio IC. It could be putting just enough out on AM to seem like its working, and then not enough for side band.

look at the caps near the finals. Look for a burn one, or one that could be twisted, or shorted in any way.

May 01, 2009 | Cobra 148 GTL 120-Channels Base CB Radio

5 Answers

Cobra 148gtl


i am having this trouble as well. The ics was my thought too, but I think it is in the modulation circuit somewhere. another article i read said to check this. "Look for the collector of TR-23, you should read about 4.5 V with a dead key. If you find that this voltage is not present, check on the opposite side of R-120 for 6.5V. Most likely this voltage will not be present; if this is the case, C18 has shorted and needs to be replaced. This is a 330uf, 10V electrolytic capacitor beside L31. To prevent "future" problems, replace with a 16V unit." As of yet, i havent gotten that far. note this is from the cobra 2000, but they are very much alike. you might cross check the resistor capacitor numbers though. btw, isnt the mb3756 the pll ic?

Jan 28, 2007 | Cobra 148 GTL 120-Channels Base CB Radio

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