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Cobra 29, no sound, burned components

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beef15
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Cobra 29, no sound, burned components

Post by beef15 » Wednesday, 01 August 2018, 11:09 AM

I have a Cobra 29 WXNWBT turns on, meter moves, channel display works, antenna light illuminates when keyed, think the TX did, no sound from the speaker on CB or WX.

Opened it up, found some burned looking components, I do not know the nomenclature, hoping someone can tell me what these are so I can get replacements and also what may have happened to cook them.

The little black cylinder with yellow wires on the positive terminal of the the power cord receptacle soldered to L201?

L10 a little black cylinder about 1/2" long with red, yellow, and black wires coming out both sides?

FL, a small black cube with LTU 455HT written on it?

Found a manual I think IDs the first two as ferrite beads, searching the part numbers is not bearing fruit though.

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Re: Cobra 29, no sound, burned components

Post by sonoma » Wednesday, 01 August 2018, 23:44 PM

take a look on Cobra's web pages and see if they have your radio listed. might help.

http://downloads.cobra.com/CB/Models/29-SERIES/



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Re: Cobra 29, no sound, burned components

Post by MDYoungblood » Thursday, 02 August 2018, 6:25 AM

A quick test to see if it is the audio circuit is to plug a speaker into the "EX SP" jack on the back and try the "PA" jack to see if the PA works. If not the problem might be in the microphone, it also could be the bluetooth. The little round cylinders you are refering to are probably capacitors, they usually have their value and voltage written on them.

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beef15
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Re: Cobra 29, no sound, burned components

Post by beef15 » Thursday, 02 August 2018, 10:32 AM

In case pics will help...

Cylinder on the power in wire, spewed brown resin/fluid on the component beside it, they were stuck together by this substance, copper bend showing on the end has corrosion
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Another angle of the input cylinder, and the one with six leads which also cooked out whatever fluid that hardened
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And what I believe is a filter/crystal? again has the burnt on resin/fluid
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MDYoungblood
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Re: Cobra 29, no sound, burned components

Post by MDYoungblood » Thursday, 02 August 2018, 11:39 AM

Okay, the first 2 pics are caps, boy did they overheat, you can change them out with the same value but can go with a higher voltage, 16v caps is what I would use, sorry but I haven't a clue their value. The last pic is a filter crystal, can probably find it on the internet. You could check our sponsor, CB World, viewforum.php?f=117 ,for parts, he does carry some for Uniden and Cobra.

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beef15
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Re: Cobra 29, no sound, burned components

Post by beef15 » Saturday, 04 August 2018, 8:15 AM

Little more looking, first two pics I believe are ferrites, the lower component in the second picture is actually a tube around three insulated wires. Also found another small one that looks to have been overheated. Not sure if they are damaged or it's just a coating cooked off, whatever it is it is corrosive, the one in the first picture on the main power wire has a wire bend that comes out that is quite corroded.

What could cause this? 12V mobile unit, happened while sitting idle for a year or two, proper inline fuse, turned off with the antenna removed. Close proximity lightning strike? Do believe we had one of those.

Can any 455hz filter crystal with the right pin out be used? LTU 455HT doesn't seem to be available.



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Re: Cobra 29, no sound, burned components

Post by MDYoungblood » Saturday, 04 August 2018, 10:06 AM

If they are beads they probably can be reused with new wires installed, the 455 filter could probably get out of a donor/parts radio. I have no clue on how that could have happened.

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