Question about Cobra 25 LTD 40-Channels Base CB Radio

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No power when i plug in fuse keeps popping,even with a 30 amp. like something shorted out on in side

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You are so right, there is a short.. This is usually a result of hooking the power leads up in reverse-polarity. As a result, the protection diode shorts, preventing the death of the rest of the radio. This diode, a solder-in part, is found on the pc board, next to the red wire that connects from the DC power jack. A 1.5 amp general purpose diode will work. And don't use a 30 amp fuse.

Posted on Jan 23, 2009

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1 Answer

Got pop noise

Popping sounds are from the the ignition - spark plugs, wires and distributor. Most modern cars have "radio resistor plugs" & "spark plug wires" installed from the factory. If unsure on an older car, check under the hood and inspect the wires & plugs.

Make sure your radio AND antenna system are solidy grounded. Poor grounds can allow all kinds of strange sounds and erratic behavior from the radio.

Also, connect the + & - power leads DIRECTLY to the battery. You can pass the + lead through a dedicated relay that opens when the key is removed if you want, but avoid like the plague connecting the + lead to a terminal in the fuse box and the - lead to an arbitrary grounded point on the body. Direct connections to the battery helps to prevent a way for noise to enter the radio on the power leads.

You may also be hearing the electric fuel pump located in the fuel tank on many newer cars. Solving that sound is very difficult.

Good luck!

Jan 12, 2013 | Galaxy Radios DX- 88HL Base CB Radio

1 Answer

How to check wiring inside a cobra 25 classic to determine if its made propperly

Yes, if you have a meter check resistance (like reading a fuse) with the radio off and power cord removed.

Only two of the three pins (look at power cord to see only two have metal in them) are used.

With power switch on front in off position there should be no reading across the + to - pins on the back of the radio.

If a short there the protect diode is shorted--likely first time it got hooked up backwards--easy to do.

Follow in this case the + pin on back just inside the radio and it goes directly to a diode. cut the diode if a short there and read again at the plug--if short gone replace the diode--radio will work without it but you will have no protection in that case.


Jun 02, 2012 | Cobra 29 LTD CB Radio

1 Answer

Keeps blowing in line fuse when i turn it on

  • If your blowing your inline fuse you have a direct short. If someone was in your radio tuning it up then check for a capacitor or resistor or other electrical component leaning over.
  • Check the tip connector of the power wire. There is a screw on the connector that goes into the radio. remove it and have a look make sure the connection is solid. Please note that even with 3 pins on the connector only two are used.
  • Somewhere you have a short and you need to look good and find it. If you have further information on what was going on right before this short was noticed feel free to post it here.
  • If you just had a tune up on your CB you can move up to a 4 Amp fuse and thanks it. The stock one is 3 Amp.

  • If you have any comments please feel free to leave them here.
  • Hope this helps and thank you for using FixYa.

Regards, Tony

Sep 29, 2011 | Cobra 29 LTD CB Radio

1 Answer

The power wire hook up for the trc-481 cb radio

  • Hi, I can help.

  • If you have any comments please feel free to leave them here.
  • Hope this helps and thank you for using FixYa.

Regards, Tony

Sep 18, 2011 | Radio Shack Radio Communications

1 Answer

What fuse does my maxon mcb-30 cb take

12 volt 2 amp kinds or any 0.5 amps even. You want it to blow fast to save radio from damage. So, any type 0.1 amp to 1 amp or 2 even. It doesn't matter; but a fast blowing one will save radio from damage later on.

Apr 04, 2011 | Maxon MCB-30 40-Channels Base CB Radio

3 Answers

My Midland 1001Z 40-Channels Base CB Radio keep popping my fuse. I'm not getting any power to it. What to do ?

Hi erve, my name is John. Welcome to FixYa. You need a 2amp fuse, make sure you have the correct polarity, red wire (+) to the hot, and the ground (-) to the ground side. It is best to run the unit to the battery. If still no avail, let me know, I will have further solution. Thanks for choosing FixYa...John

Dec 06, 2010 | Midland 1001Z 40-Channels Base CB Radio

1 Answer

CB keeps blowing fuses

There are a few common reasons the fuse keeps blowing:

1. The transmitter final transistor is bad, it usually is directly connected to the 12v source and not switched by the power switch.
2. The power wires were accidentally reversed I.E. positive to ground, neg to 12v. There is a protection diode on the circuit board that did its job and is now shorted. it will keep blowing fuses until its replaced.

Dec 30, 2008 | Cobra 18 WX ST 40-Channels Base CB Radio

1 Answer


This may be a dumb question, but have you tried replacing the fuse in the power wire? That fuse blowing might have been the pop you heard. It is possible that you did short something out, though I have never had that happen by messing with the wires for the PA.

If replacing the fuse does not help, and you know that there is still good power and ground coming out of the power plug, you may want to try replacing the protection diode.

That is where I would begin, the fuse, power and ground coming into the radio, and then the protection diode. If nothing helps, please let me know.

Dean Pitts
Rollin CBs

Oct 04, 2008 | Cobra 29 LTD CB Radio

1 Answer

B;owing fuses, wont power up, just smokes


Try checking the reverse protection diode. This diode would normally be connected right after the power connector and would be the biggest diode inside. One way to verify if this is defective and causing the fuse to blow is even with the power switch at the OFF position, the fuse will still blow.

If on the other hand, the reverse protection diode is good and fuse will not blow when power switch is at OFF, then the short/defective component is inside. There would only be two (2) major components that can cause the fuse to blow with the power switch to ON, the final transistor and/or the audio IC.

Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FixYa.

Jun 06, 2008 | Cobra 29 LTD CB Radio

3 Answers

Keep blowing fuses

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 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 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

May 11, 2008 | Cobra 29 LTD CB Radio

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