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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  • 9 Answers

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

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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. .

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1 Answer

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Hello Rob55spiral, Most common malfunction in no modulation is the microphone. Swap out with a known working mic. #1 If problem is corrected, aquire a DVM and repair the broken cable connection in your microphone. #2 If still no modulation you have an internal componet malfunction. Please inform me of results.

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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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