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Re: 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.
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You have a bad diode near back. Probably the black fat one with a stripe. Its located near power leads and audio transformer in one corner. Change all Black Diodes with (White) stripes in back. You must of crosswired it blowing the diode.
Hi, Great radio when it works. If you have your settings on CB - not PA - -be sure that your Cobra has that setting selected. If CB -is selected and still nothing - be sure you have a working mic. These wires are fragile and can break internally. One easy way to check is to borrow a cobra mic or even drop by a CB repair shop and ask them to do a mic check with the mic - it is free.
If you have a bad mic replace it and all should be well. If your mic is good and it still doesn't transmit you will need to replace the finals in the unit. It is common that these burn out of you got too close to someone with too powerful a radio. The CB shop will need to look at it further and repairs should not be over about 40.00.
if you smell something like burned plastic i am afraid you have had a shortage inside your cb. most of the time that means certian death for electronic. if you now of a cb repair shop they may be able to fix your problem.
Had fixed the same problem yesterday. My cobra worked when it wanted to, when it didn't it looked like you explained. I found out that on my cobra the blue wire on the mike connector was broken. When it disconnects, no sound. after soldering, everything works fine.
You have some form of short circuit in your CB, most likley I would suspect the Power supply or the RF Power Output Amplifier. Here are some basic instruction on how to tell wher the smoke is coming from.
1) disconnect and remove your CB from your vehicle and put it on a workbench 2) remove the cover from your CB and expose the circuit board to view 3) connect your CB to an external 12 volt power source and antenna or a dummy load 4) power up the CB and determine where the smoke is coming from then turn off the power supply to the CB 5) At this point you will need a schematic of your CB (get one from www.servicemanuals.com) 6) find the point on the schematic that relates to the point where the smoke is coming from 7) using a ohmmeter determine which component and or components are shorted 8) replace the shorted and or malfunctioning components. 9) test the system (power on, transmit and receive) 10) close the unit back up 11) reinstall into vehicle 12) run tests again.
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.