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Cobra 148GTL - TX and RX Issues

johnnc

New Member
Mar 7, 2014
2
0
1
Hey All,

I am completely new to CB in that I have never looked at the inside of one of these things. I use them in my 4x4 and motorhome. I am technical in that I can solder and can follow instruction. I don't understand how these things work.

I have a mid-1990s 148 that I had overhauled last year. The radio was cleaned up, numerous parts were replaced, some upgraded, etc. This radio lives in my motorhome and is used on a limited basis during a caravan and at camp when we are wheeling. The last 2 trips I used the radio a lot more than normal.

About 2 hours into each trip the RX volume would start to get quieter and quieter until it was impossible to hear anyone. When I TX, guys in my caravan could hear me but my TX became quieter and quieter. I turned off the radio both times, waited an hour, and everything worked as normal.

I am guessing something is getting hot and performance is being affected.

I emailed the guy who did the work but he is very busy and just told me to send him the radio, more money, and he would get to it in 6-8 weeks. I don't want to do that until I understand more about what is going on with this thing. I also want to be clear in that I do not blame the guy who did the work in any way. This thing was DOA when he got it and it is beautiful today.

Any help is greatly appreciated.

John
 

It might be better served to send it to a shop - IMO.

But if you are adventurous, then get a can of air and spray a small group of transistors at a time after the problem appears. If one area causes the radio to come back up after the cool air spray, then try to whittle down the area in which you sprayed. If the cause is a thermal problem with a transistor, that may help locate it. Check the voltage regulator area first, and then work your way into the audio chip. That would be my guess from what you have described.

It may also be an electrolytic cap failure, so cooling spray may not help at all in locating that problem.

If all else fails, then send it into a reputable shop.
 
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