CB keeps blowing fuses

final or main IC getting ready to burn out.Have it checked by a tech.If its the final then replace the driver also.

Cobra 18WX ST II

change the reverse polarity diode. Put one in that is one number higher like 1n4003 to a 1n4004 .It will handle more volts so you shouldn't blow any fuses.

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.

If it is just a blown protection diode, it is only a $10 fix at most any cb radio shop.


If I can help anymore, please let me know.

Dean Pitts
Rollin CBs
[email protected]

Check bias and check your SWR. Also make sure your coax is not excessively leaky, and also check the loading coil inside the antenna to make sure the coil connections have not become all corroded and that their connections are sound.

d23 a 1n4004 diode second component from pa speaker port inside radio has failed. It is most likely that neg/pos polarity has been switched shorting this diode. It is there to protect your radio from reverse polarity as so it is names the "protection diode." 2 solutions first not recommended.

1. Cut the diode this will stop the directed grounding that is continuing to blow your fuse.
2. Go get a pack of 1n4004 and rosin core silver solder from radio shack and replace it paying attention to the direction it is installed.

just a side note the solder trace often burns in this area so a jumper wire soldered in around this bad area solder side maybe needed.

Hi and welcome to FixYa,

Initially, check the reverse protection diode, D18 (1N4004). It would be located / connected at the power board of the DC connector.

Good luck and thank you for asking FixYa.

Is the wire going to the battery touching chasis ground at all? Accidentally pinched it, cut wire etc? If not the the power supply may be fried.

Your polarity protection diode has been blown. If you tried hooking up your CB and accidentally pushed the plug in backwards. Inside the radio, there are 2 big black diodes near the transformers, D8 and D23. Replace these with the same or bigger. You can the burnt one out and the radio will work, but if you hook it up wrong again, it will fry the radio.

Hi,

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.