Question about Radio Shack TRC-503 CB Radio

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Radio shack cb radio 21-1703

Stupidly I plugged it into a wall outlet and, of course the fuse blew. I can't find a 2A 125V fuse. Only a 2A 250V. No power. I connected the wires to a cigarette lighter plug. No power. I tried it touching the two ends without a fuse. Still no power. If the fuse blew, isn't the unit still protected? Suggestion?

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  • SBarnes Jul 17, 2008

    Thank you for the response. I only plugged it into the wall once (first). No other fuses have blown but maybe the wall power blew the diode you mentioned? If so, if I can see which item is the particular diode, I'd like to try to solder in a replacement myself (more satisfying).


  • Dean Pitts
    Dean Pitts May 11, 2010

    There is a protection diode, which probably blew. This usually happens when the power and ground wires are connected in reverse. I assume this is probably what happened, though I am not positive since you connected to ac instead of dc power. The reason the fuse keeps blowing is that with the diode blown, there is now a short between ground and power, which is to prevent further damage to the radio. You should be able to take it to a cb repair shop and have them solder a new protection diode in place for either $10 or $15, as long as that is all that was damaged.

    As for the fuse, a 2a or 3a 250v will be fine. Typical tube fuses you find in parts stores or electronic stores will be rated at 250V. You need to be more concerned about the amps not the voltage. The higher the amp rating, the more amperage is allowed through, which can damage parts during a power surge.



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OK. I do not know the exact number for the diode off hand, because I don't have the same radio in front of me. On most cb radios, this diode is usually located on the component side of the pc board, close to where the positive lead solders to the board. Most of the time when it burns, it just becomes brittle.

If you do replace it on your own. The diode is called a rectifier diode, which you can pick up at radio shack or at The part number is between 1N4001 to 1N4008. When installing be sure to observe polarity, making sure that the side with the silver band is facing the direction of the arrow.

If I can help anymore, please don't hesitate to ask.

Dean Pitts
Rollin CBs

Posted on Jul 19, 2008

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