Question about Cobra 29 LTD CB Radio

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Keep blowing fuses

I keep blowing fuses when I plug in power cord.

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  • Anonymous Aug 04, 2008

    i used 18 watt speaker wire and wired my cb radio to the batterie with it and it keeps blowing the fuses.

  • powerwagon78 Aug 06, 2008

    i plug the power cord in and i instantly blow a fuse

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3 Answers

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More than likely the power plug was turned around the wrong way when plugged in, and it burned ou the protection diode. This is a very common thing to happen and very easy to fix.

If you have and can use an ohm meter, any multimeter than can check resistance works, pu it on the Rx1 scale and put the black test lead to the black power lead and the red test lead to the red power lead. If you blew the diode, it will show up as a short, which is about 0 ohms, or continuity. Then reverse the red and black ohmmeter test leads, red to balck and black to red. It should still show a short.

Note: On a few CBs, the diode comes after the On/Off switch in the circuit, so you may not see the short until you turn the power switch "On".

If this is burned, reply here or you can send me an email at rollincbmods@yahoo.com and I will walk you through the changing of the diode. To change it, you need a rectifier diode you can pick up at Radio shack, I believe any one between 1N4001 through 1N4007 will work. I believe the radio shack down the road from me carries the 1N4005. If you don't have a radio shack, go to www.partsexpress.com and order one. I oder from them all the time, they are a very reliable company. They carry the 1N4007 for $0.09 each.

You also need to have a desoldering iron, or some thing to remove solder from a cuircuit board, a soldering iron, solder, and a pair or needle nose pliers or something to hold the diode.

Once you are ready, like I said, let me know and I will tell you which number it is in the radio, how to locate it, and what to do to replace it.

Dean Pitts
Rollin CBs
Mt. Vernon, TX

Posted on May 12, 2008

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You may have a shorted power amp... check for ic's that may be defective. desolder the suspect ic and then test the power again.

Posted on May 12, 2008

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1 Answer

Midland cb keeps blowing fuses


depending on which model it is there is a reverse polarity diode near the power cord that connects the radio . If it was connected wrong no matter how many fuses you insert it will keep blowing them. You have to change that diode in order to get the radio to work. If you still have the fuse problem then take it to a tech and let him fix it.

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Tip

GET YOUR BLOWN UP RADIO BACK ONLINE.


When you cant get your radio turned on. All it does is blow the fuse imeadiatlly hooking it to power. Most likely it is the (reverse polarity diode). The quick fix is to locate your diode? This diode usually is back behind a coil wound transformer on your board inside the radio and in the general area of where the possitive ans negative plug wires solder to the board! Usually it is black with a silver band around one end. If you clip it on one end or remove it this will restore your radios power. CAUTION:: When doing this ALWAYS use a dual fuse power cord . This will prevent this from happening again by blowing the fuse first. Doing this procedure will remove your thermal protection to the radio thus making it wide open to being fried for good if it ever gets hooked up backwards again. This is my reasoning for the dual fused power cord. Good luck!

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Where did you buy the radio at? Can you return it to the store? If you purchased it at a big box store, like Walmart, they will take it back without a receipt on an exchange.

More than likely the radio was wired backwards by someone, which blew the protection diode, and then was returned to the store and put back on the shelf.

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If I can help anymore, please let me know.

Dean Pitts
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dean@rollincb.com

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have you been using the uniden pc68ltw cb radio without the fuse blowing before?

If the uniden pc68ltw cb radio has not been blowing fuse before, then might be a problem from the radio. This problem should be a power related problem.

The fuse blowing means there is excess of current. So while your trying to refuse, thicken the wire.

Best regards.


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