Cobra 29 ltd no receive from speaker

[That_guy_in_wv]

Nice!!!!!! It works, I'm guessing that whatever blew the speaker that was in it when I got it also got to the one I put into it shortly after I turned it back on so one of the many parts I swapped out was shorting the speaker and blowing them up. Thanks all of you who tried to help with this problem y'all really do know what your doing and help quite a few people each time someone has a problem. Most sites dont do that or threads end with the problem never answered.

Again I appreciate all you guys do and thanks for the help.

That_guy_in_wv

 

[midnight special]

both of my 29s that i set up on my desk recieves out the pa,,,,,the one in my pickup ,,,another 29 recieves out the pa,,,,,i just turn squelch up all the way or turn rf gain all the way down if i dont need to listen to radio and do any dog calling,,,,, so i guess i have 3 broken cobra 29s,,,,,

 

[OldTech03]

Well There is only one thing that will pop a speaker that quickly and that is a DC voltage or a speaker that was faulty before you put it in the unit but you should always be using a known GOOD bench speaker when troubleshooting a radio if you had plugged a bench speaker into the unit under test you would have found this issue in less than 10 seconds???? Just sayin! and you should always protect the bench speaker with isolation that way you don't blow your test speaker/bench speaker in the event there is a DC voltage present on the line it may sound like overkill and it may only be an issue in 1 out of 1000 radios but it's that one time you always remember. I'm still in a bad mood damn gotta get out of it. LOL

 

[That_guy_in_wv]

Midnight special If I knew for sure what parts made my internal speaker and pa work right again I'd tell you but all I really know is I swapped out tr3, tr17, tr18, c52, c66, c71, R51 and the pa and external speaker jack. You might not need to change all those but I didnt know my new speaker had been burnt up by the radio by the time I had all them swapped out. I believe tr3 and tr18 are both switching transistors for tx/rx if I remember right one or the other. More then likely it was my jack on the back shorted or one of those tr's or caps shorted. Wish I could help more. I was in a cobra 29 ltd classic april 3 2008, KEPC-1106 board with a mfg date on the back, of march 2010. Hope that helps, it sounds like the same problem I had receive through the pa but my internal speaker didn't work either. Maybe someone with more knowledge in the pa section of the radio can assist with it.

 

[guitar_199]

Seriously, I don't intend that this be as indicting as it may sound...Just a question.....

Do you have any kind of scope or signal tracing equipment? Meter with AC? or an Audio tracing probe of some kind?

Looking at schematics, defining the components involved in a function and replacing them can get expensive... and risky! Changing parts carries the risk of damaging the parts you remove or the PCB itself.

I like to try to figure out what part is dead before changing anything.

Midnight special If I knew for sure what parts made my internal speaker and pa work right again I'd tell you but all I really know is I swapped out tr3, tr17, tr18, c52, c66, c71, R51 and the pa and external speaker jack. You might not need to change all those but I didnt know my new speaker had been burnt up by the radio by the time I had all them swapped out. I believe tr3 and tr18 are both switching transistors for tx/rx if I remember right one or the other. More then likely it was my jack on the back shorted or one of those tr's or caps shorted. Wish I could help more. I was in a cobra 29 ltd classic april 3 2008, KEPC-1106 board with a mfg date on the back, of march 2010. Hope that helps, it sounds like the same problem I had receive through the pa but my internal speaker didn't work either. Maybe someone with more knowledge in the pa section of the radio can assist with it.

 

[OldTech03]

Ok, I let us try this one more time, Why? Anyway, you stated that it received, I know this because if you plugged in an extension speaker you were able to here the receiver RIGHT? So there would not have been any reason to replace any of the parts you replaced. So that means there is still something totally unrelated to what you did or at least what you told us you did that now has the radio working?

 

[That_guy_in_wv]

It only takes a second to swap parts, the voltages were off on the parts I swapped, the caps I changed were 10volt and 16volt i put in higher voltage (so maybe they wouldnt short again) I was checking out the radio where I had just got it, I didn't say this because someone said not to tell just what all parts I changed so i didnt think it mattered to explain where it wasn't stated in the thread header. Some that were supposed to be 0.0 volt were reading 0.5v and others that were supposed to read 4.8v were 7.8v no sense in leaving in parts while I'm there that are showing voltage that's more then the voltage chart shows it to be. I have a sinad, digital voltmeter, frequency counter and signal generator but not everyone has those things. Its mostly a hobby for me and learning what I can and using just a voltmeter is what most would be doing if it were somewhere else. Like I said in an earlier post I didn't want to drag out a bunch of test equipment. I figured in the almost 40k members on here maybe someone has had around the same problem before and they have. I've spent a lot of time online before reading without all the test equipment figuring it out myself and most people who look up what problem I've had will be only using a volt meter in most cases so wouldnt it be hard for them if we just said take a scope or some meter they didn't have and try to explain it. It might be the right way but sometimes it's not possible, Again sorry I'm not sure exactly what part made audio come back to the speaker wires.