Ok, so I have a Cobra 29 LTD classic that is not powering up at all. I know it's not my wiring or fuse in the link because I have a 23 channel cobra 29, i plug in the same plug an it powers up fine plus I took my multimeter to the back of the plug where it enters the radio and there is power there. I have no repair shops anywhere near me at all to take it to. I would really like to get the radio working again. I have the schematic, but I am no expert. Any direction at all would help. Thanks in advance.
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Cobra 29 LTD no power
- Thread starter cowboy2tough2tame
- Start date
Open the bottom cover and near the rear is the small square audio transformer. Near where the power comes in. Right behind it is a small diode, (black with a silver ring on one end). Looks like a little bitty firecracker. Go get one just like it down at Rat Shak or somewhere, and come home and clip the old one out with some good snips leaving the wire standing where it comes out of the circuit board. Solder the two ends onto those two clipped wires, and maybe.......shazam. Fixed!!!!!
Seriously, that little diode is what usually stops current when something goes awry.
Good luck!
Buddy S.
Seriously, that little diode is what usually stops current when something goes awry.
Good luck!
Buddy S.
I believe I see the diode you are referring to, but just to make sure, it's C23 correct? Boxed in red in the photo.
Thats the one. If that does'nt work, you'll have to wait on somebody WAY smarter than me that might have an answer. But tracing dc to where it stops would probably be next thing to do.
The diode in question is usually bad when there is no power. Sometimes cracked or burned.
Good luck
The diode in question is usually bad when there is no power. Sometimes cracked or burned.
Good luck
many times the pertect diode even looks good , but it's bad. You can desolder it from the board , if the radio comes on , that was your problem , by all means , replace it . You can run the radio without the diode BUT if you hook her up backwards with out a fuse in line on the power cord you will start frying things , but at least you can try it without the diode in line to see if that was the problem. Let us know.
Can that diode be bad and still have voltage running through it? I took out my multimeter, had the negative side sitting on where the power comes in on the negative side of the diode that bridges the positive and negative (the far side of the black diode with the silver band that is up by the red and white speaker wires in the below photo) and took the positive side and checked both sides of the diode and it has voltage.
"....clip the old one out with some good snips leaving the wire standing where it comes out of the circuit board. Solder the two ends onto those two clipped wires, and maybe.......shazam. Fixed!!!!!"
tacky. remove the component and the leads entirely from the trace lands, clean out the holes and re-install the new component. solder the leads of the new device at the circuit board.
tacky. remove the component and the leads entirely from the trace lands, clean out the holes and re-install the new component. solder the leads of the new device at the circuit board.
Damn ! I didn't catch that Freecell ! I don't think you meant what you said 100 . You DO NOT want to jumper that diode ! you want to remove it as we said , the power there is meant to go in one direction only , that's what the diodes for , if you jumped it , power would go the wrong way as well , then your looking for trouble , that's why the diode is there in the first place , this is why they put fuses in line with the power cords as well.
Protect diodes usely go because the radio was hooked up backwards without a fuse in line on the power cord or maybe there was to big of a rated fuse in line with the power cord when hooked up backwards ? this could also blow the diode. The fuse inline with the power cord and the diode in the radio are both to protect the radio from further damages and our investments. I believe the 29s run a 2 amp fuse in the power cord , you hook it up backwards , the fuse goes instead of the diode in the radio , you hook it up with much larger fuse rating backwards , the diode might go as well. You hook it up backwards without a fuse inline , diode goes bye bye. So in other words , it's a lot easier to change a fuse in the power line then it is to change the radios protect diode. You confused yet. (-:
Protect diodes usely go because the radio was hooked up backwards without a fuse in line on the power cord or maybe there was to big of a rated fuse in line with the power cord when hooked up backwards ? this could also blow the diode. The fuse inline with the power cord and the diode in the radio are both to protect the radio from further damages and our investments. I believe the 29s run a 2 amp fuse in the power cord , you hook it up backwards , the fuse goes instead of the diode in the radio , you hook it up with much larger fuse rating backwards , the diode might go as well. You hook it up backwards without a fuse inline , diode goes bye bye. So in other words , it's a lot easier to change a fuse in the power line then it is to change the radios protect diode. You confused yet. (-:
What I told him might be "tacky" Freecell, but it'll work best for him.
When's the last time you saw a new guy remove the bottom cover off a Cobra 29, (when he's never done it before), heat up a big old pistol iron and muck around on the bottom of a board? Thats what I thought. Sometimes we have to "think" a little bit, right? Maybe everyone's not an accomplished tech.
He'll have a MUCH better chance of having a radio left if he just clips the diode out and resolders the new one in from the top onto the old leads. If he pays attention to the direction to install the new diode.
When's the last time you saw a new guy remove the bottom cover off a Cobra 29, (when he's never done it before), heat up a big old pistol iron and muck around on the bottom of a board? Thats what I thought. Sometimes we have to "think" a little bit, right? Maybe everyone's not an accomplished tech.
He'll have a MUCH better chance of having a radio left if he just clips the diode out and resolders the new one in from the top onto the old leads. If he pays attention to the direction to install the new diode.
OK , IM freaking confused now ! What the heck ! clip this clip that add wires to clip ? Freecell ain't no dummy, and with my limited skills , protect diode bad , you remove it , (radio should work then) at least that way you know the diode was the problem then you can change in a new one.
It just seems back and forth here , someone care to take the key board time to explain in a civil manner ? Good luck to you cowboy. IM done here.
It just seems back and forth here , someone care to take the key board time to explain in a civil manner ? Good luck to you cowboy. IM done here.
use the PROPER tools and replace the defective component by removing all trace of it and re-insert the new one INTO THE CIRCUIT BOARD. if you don't like the answer then don't ask the question. anything worth doing is worth doing right. maybe we should ask cowboy if he knows how to solder properly too. large pistol irons are designed for heavy point-to-point wiring, not printed circuit board work.
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Man , IM getting old , I see what you meant now 100 , it was just the way you explained it , you were refering to the "cut leads" of the clipped diode refering to them as "wires" ,and this is why I first thought "you" meant jumping the leads and I now see you meant resoldering the diode to the clipped "leads",rather then "wires" and I now get what freecell meant by "tacky" a little less then I first did. My first thought was you were telling hime to jumper the diode which you don't want to do. IM sorry I read you wrong 100 , your way would work , as well as Freecells more professional way of doing it.
The simpliest way would be to clip the top of the diode leave a little leads exposed on both sides , spread them slightly apart , now see if the radio fires up ? if it does , you know it was the diode and then you can replace it ,if it doesn't fire up ? it's possible it wasn't the diode and you can just push it back together and put a dot of solder back on the leads , Tacky ? I suppose , but it beats a sharp stick in the eye. So in the end , your way would work 100. I've got to be done now
The simpliest way would be to clip the top of the diode leave a little leads exposed on both sides , spread them slightly apart , now see if the radio fires up ? if it does , you know it was the diode and then you can replace it ,if it doesn't fire up ? it's possible it wasn't the diode and you can just push it back together and put a dot of solder back on the leads , Tacky ? I suppose , but it beats a sharp stick in the eye. So in the end , your way would work 100. I've got to be done now
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Good greif Freecell!!!! Here we have a cowboy that has never looked in a radio before, and you want him to perform a repair job like he's been a tech for 30 years. OK, I'll try this. Ever seen ANYBODY that does'nt know what they are doing jackin' around on the bottom of a circuit board with a soldering iron of any type? There won't be a radio left when its all said and done.
We all understand you're a pro and would like to see it done correctly. But it ain't gonna get done with this guy, but for the easy way.....IF then.
Now if I ask you something, I could do it your way because I have ruined hundreds of dollars worth of pills, finals, potentiometers, meters, melted wires, tore traces galore, and fried entire boards.
I would just like to see this guy be able to say Break 19 for a radio check again, with THIS radio.
I'm steppin' down!!
We all understand you're a pro and would like to see it done correctly. But it ain't gonna get done with this guy, but for the easy way.....IF then.
Now if I ask you something, I could do it your way because I have ruined hundreds of dollars worth of pills, finals, potentiometers, meters, melted wires, tore traces galore, and fried entire boards.
I would just like to see this guy be able to say Break 19 for a radio check again, with THIS radio.
I'm steppin' down!!
You might have to check the foil traces under the diod to make sure the havent burnt, it has hapended, not often but it still does happen.
Hawk
Hand from the Iron City
Hawk
Hand from the Iron City
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