Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Cobra 29 won't power on

Treefork

Treefork

Member
Dec 12, 2011
22
2
13
Indiana
I have a Cobra 29 LX (2011) with the digital screen and meter. It won't power on. I took it out of the truck one weekend for truck repairs then when I went to plug it back in it wouldn't power. Fuse was blown, replaced fuse and still wouldn't power, switched to my other radio with same power connector and it worked fine.

Is there anything I can look for that might give me a clue like a specific blown circuit or something? I don't have any techs in the area and I drive local so don't get out of town often. I can post a photo of the circuit board if that would even be useful.

Joe
 

Blown protection diode D23 very close to the power plug on the board. Most common fault if the radio is plugged in wrong. You can clip it out to see if the radio works. But if it works; you better replace it or else there is no more protection and then the radio will really fry if you make the same mistake again. Use a 1n4003 diode (5-25 cents each depending on where you buy it) to replace it. If the part you are taking out is a surface mount part, you can use a standard 1n4003 diode if you solder carefully. Just remember to orient the band in the same direction as the diode you are taking out. Diodes are a polarized part and must be put in the same way/polarity as the original part was.
 
Robb said:
Blown protection diode D23 very close to the power plug on the board. Most common fault if the radio is plugged in wrong. You can clip it out to see if the radio works. But if it works; you better replace it or else there is no more protection and then the radio will really fry if you make the same mistake again. Use a 1n4003 diode (5-25 cents each depending on where you buy it) to replace it. If the part you are taking out is a surface mount part, you can use a standard 1n4003 diode if you solder carefully. Just remember to orient the band in the same direction as the diode you are taking out. Diodes are a polarized part and must be put in the same way/polarity as the original part was.
Click to expand...

Boy that thing doesn't want to be found. :) I'll keep looking.

Found it. Looks ok though. Would it have visible damage to it?

Ok, well either way, didn't power up after clipping it. Need a new diode either way. :)
 
Last edited:
Just a thought, try moving the power cord up and down at the back of the radio. I've seen a few come loose where the pins come through and connect to the board. Usually older radios that have been unplugged a lot. Use a volt meter to see if you have power where the positve pin connects to the board. Just a guess, good luck.
 
Half the time, when the protection diode is fried, a trace is also burnt and you have to repair the trace. Radio facing you, top cover off, back left corner, about an inch in from back and left side. See if it's burnt. Lightly scrape off the green where it's burnt so the shiny gold trace is shown. Solder it. You can run a jumper instead but I don't recommend that.
 
  • Like
Reactions: Josip
CbRadiosPRONTO said:
Half the time, when the protection diode is fried, a trace is also burnt and you have to repair the trace. Radio facing you, top cover off, back left corner, about an inch in from back and left side. See if it's burnt. Lightly scrape off the green where it's burnt so the shiny gold trace is shown. Solder it. You can run a jumper instead but I don't recommend that.
Click to expand...


ImageUploadedByTapatalk1406510595.207240.jpg

Here's that section. Anything look out of place? How so I know if it's burnt?
 
Confused me for a minute. You turned the picture sideways.

Make sure you replace the diode or you might do more damage than that one trace the next time you plug it in backwards. Everybody plugs them in backwards at some point. You'd think it won't fit backwards but they get close enough to touch.

Congrats!
 
I mark all my radios with a sharpie these days a big + sign on the pos side and same for neg side. Helps!!
 
CbRadiosPRONTO said:
Confused me for a minute. You turned the picture sideways.

Make sure you replace the diode or you might do more damage than that one trace the next time you plug it in backwards. Everybody plugs them in backwards at some point. You'd think it won't fit backwards but they get close enough to touch.

Congrats!
Click to expand...


I was trying to think when I might have crossed wires, but now it makes sense, I do remember trying to plug it in and then having to turn it. Must be what I did.
 

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back