| Author |
Message |
    
Stumpjumper
| | Posted on Tuesday, February 18, 2003 - 7:28 pm: | 
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I have a Cobra 2000 CB radio and I am having trouble with it.
Yesterday I talked to someone on the other side of the U.S. and today I turn it on and I try to talk to local people and no one answers. I hear them fine but they are not hearing me. I called up a friend that lives close by and he turned his mobile on and he couldn't hear me but I could hear him. This is on AM and SSB.
I disconnected my amp and it still does the same thing. I even changed the battery in my astatic mic and same problem. I even tried the mic that came with the radio, and still no luck.
Can someone help me out here. |
2600
| | Posted on Tuesday, February 18, 2003 - 11:57 pm: |
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Hey Stumpjumper, can you handle a soldering iron and a voltmeter? If so, there are a couple of things to try BEFORE messing with the finals, driver OR modulator. That's the advice you will hear first, but hold off doing that for now.
You said one important thing: "Taiwan". This radio is probably old enough to get a driver's license. There are several small electrolytic capacitors in the radio that have a voltage rating of ten volts. A handful of them tend to fail first, before age catches up with the other 8 or 10 dozen electrolytic caps that are in the radio. One of these is C95, a 47uF 10 Volt part.
With both top and bottom covers off the radio, find IC3. It's a black rectangular chip about 3/4 of an inch long, and 1/8 inch thick. It's located parallel to the centerline of the circuit board running front to back, about two inches back from the front edge of the circuit board. It has a single row of 7 pins, and will probably be hidden under a bundle of wires running along the centerline from front to back. At the rear end of IC3 is a single electrolytic capacitor about 3/16" diameter about 7/16" tall. The white screen-printed legend "C95" to the right of it on the board. Unsolder and pull C95 from the board. Check to see that no solder has "smeared" onto adjacent connections and clean up any bridged gaps between foil traces. Now power up the radio and see if it shows power on an inline wattmeter. If C95 was bad, it will come back to life.
If this works, don't try to run it with C95 removed. It's a filtering component. You need it. Use a 25-Volt or higher rated part to replace it. It doesn't HAVE to be rated at exactly 47 uF. Nearly any value from 33 uF up to 220 uF will work, but there's no room for an oversize part where it is mounted.
And if pulling C95 loose didn't change the picture, you didn't waste a whole lot to find out your trouble is elsewhere. If this DOESN'T work, check back. There will be more questions, mostly about voltmeter readings.
73 |
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