I know i know, another cobra with no receive lol. But this one is an exception, I've repaired close to 100 different 29s over the years and I'm stumped. I bought this from a friend and he said he has to use an external speaker to hear anyone so I figured ok I'll buy it. The speaker was bad when I got it so i put a speaker in the radio no problem there, i checked it before i put it in to make sure it worked. I still had no rx so I hooked up my external and like he said it receives. Now the problem is the pa/ext works and it tx/rx like it should, but when i switched the speaker to pa I can still hear the channel I was on when I flip the switch to pa. Now the question I have is a cap shorted to make the radio not rx on the radio speaker and is it what's making the radio rx on pa jack when switched. I changed tr12 and tr13 and the tda2003 audio amp. Also changed a few ceramic caps here and there around where the pa/ext jack's and speaker is soldered on the board plus put in a schotty receive upgrade just in case those were bad. I have no clue where to go from here.
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Cobra 29 ltd no receive from speaker
- Thread starter That_guy_in_wv
- Start date
Well, first it seems your receive is fine, right? After all, reading your post it would seem that the only issue is the audio isn't being delivered to the speaker? So you just replaced a bunch of parts that had nothing to do with the problem we call that "Parts swapping" Now I'm usually pretty easy going and I don't respond like this but I'm having a bad week so I'm taking it out on you! Listen you have a radio that is most likely working fine I'm betting it was transmitting and receiving just fine and has been from the moment you first hooked it up, but audio switching is the issue. Since you have repaired hundreds of these I assume you have the service manual for these type radios and the audio switching circuits in the 29's is pretty simple and straight forward if you trace audio switching circuits in this radio it should become clear in short order just be sure the microphone circuits or wiring is what it should be first as it makes the connection for the speaker after that is pretty simple. Now I'm basing my response on what you have posted in terms of the description you gave, Sorry don't take my response personal it's me lashing out today.
Oldtech03
Oldtech03
Last edited:
have you checked the speaker jack its self. it has a spring clip inside it to make contact to complete the circuit when you unplug the speaker. verify it is good. seen a few go bad over the years
I'm going to second this suggestion. I bought a Uniden 980 with "no receive audio". Did a little creative bending inside the external speaker jack and it's worked fine ever since.
Im with Sonoma on this one.
Try jumpering around the internal shorting bar inside the external speaker jack to test if its the jack itself.
remember that the audio of the radio goes through this jack on its way to the stock speaker and you just interrupt that path with an external speaker when you plug one in.
I'll even make it easier for you, place a jumper wire from the terminal of T1 that goes to the CB/PA switch to the side of R51 (1 watt resistor) that connects to the speaker jack.
do you now have audio through the stock speaker?
if yes, then the jack is bad.
if no, your problem lies elsewhere.
LC
Try jumpering around the internal shorting bar inside the external speaker jack to test if its the jack itself.
remember that the audio of the radio goes through this jack on its way to the stock speaker and you just interrupt that path with an external speaker when you plug one in.
I'll even make it easier for you, place a jumper wire from the terminal of T1 that goes to the CB/PA switch to the side of R51 (1 watt resistor) that connects to the speaker jack.
do you now have audio through the stock speaker?
if yes, then the jack is bad.
if no, your problem lies elsewhere.
LC
Thank you all for the replies, sorry I just got in. I'll check the jacks and see but I tried shorting already and still didnt make the speaker work. It's ok OldTech03 lol. I've changed a few of the switching transistors but no difference so far. I'll have to break out my test equipment and get into it I was hoping it was just something simple. I've gotten more radios in this year with external speaker problems then most any so far.
Again thank y'all for the help.
Tgiwv
Again thank y'all for the help.
Tgiwv
Ok so I just finished changing all the switching and regulator transistors for tx/rx and nothing yet. Not saying yall are wrong by no means lol but I didnt think it was a switching problem. It switches from tx/rx just fine with an external speaker but still could have been shorted somehow. I also changed out the electrolytic caps coming and goings from them also. I'll keep yall posted when I find the single part that's stopping receive. I'll be in it most the night until more hair starts falling out of my head, what hair I have left anyways.
I also wanted to add that the center leg of tr17 was 7.8v and from my voltage charts shows it was supposed to be 4.8 in rx mode. Not sure if that helps or not but it was changed and still no difference.
I also wanted to add that the center leg of tr17 was 7.8v and from my voltage charts shows it was supposed to be 4.8 in rx mode. Not sure if that helps or not but it was changed and still no difference.
you don't need any test equipment other than a multimeter.
have a look at that section of the radio here:
you have sound coming out of the external speaker, which means all of your audio circuits are working just fine.
there is zero need to mess with them.
the only issue you are having is that when you unplug the external speaker, the signal is not being sent to the regular speaker.
the speaker jack itself does that.
unless the stock speaker you have doesn't work, or someone has messed with the wiring in this radio in such a way that the internal speaker is no longer connected to the PC board holes that they should be in; your problem is your speaker jack, or R51 itself.
you have spent a lot of time replacing parts, but have not tried replacing the parts that are the most obvious, and are trusting your testing over just trying it.
why would you not spend five minutes and give it a shot?
you came here asking for help, but won't try the things suggested.
if you just want to tell us all the parts you are replacing, that is fine, but you need to re-title your thread.
LC
have a look at that section of the radio here:
you have sound coming out of the external speaker, which means all of your audio circuits are working just fine.
there is zero need to mess with them.
the only issue you are having is that when you unplug the external speaker, the signal is not being sent to the regular speaker.
the speaker jack itself does that.
unless the stock speaker you have doesn't work, or someone has messed with the wiring in this radio in such a way that the internal speaker is no longer connected to the PC board holes that they should be in; your problem is your speaker jack, or R51 itself.
you have spent a lot of time replacing parts, but have not tried replacing the parts that are the most obvious, and are trusting your testing over just trying it.
why would you not spend five minutes and give it a shot?
you came here asking for help, but won't try the things suggested.
if you just want to tell us all the parts you are replacing, that is fine, but you need to re-title your thread.
LC
I changed most of the other parts to try to fix the condition of rx in pa mode on the pa side with an ex speaker. I figured it was a short bringing rx in pa mode. But for the radios speaker itself I tried "jumping" t1 and r51 and had no change.
Thanks again for your help loosecannon I needed that schematic i had the pdf but can't find it. I'll try changing r51 and if not that then and both pa/ext speaker jacks.
Thanks again for your help loosecannon I needed that schematic i had the pdf but can't find it. I'll try changing r51 and if not that then and both pa/ext speaker jacks.
my cobra 29 when in pa mode the recieve goes to loud speaker just like when you speak into mike,,,,,i just took it for granted that is the way it works,,,,i might be misunderstanding this but does the recieve go out to pa speaker when turned on pa?,,,,the problem i am seeing here has do with the speaker jack not making contact or shorted,,,,
ok i must've missed the part about hearing receive through the external speaker when in PA mode.
My new guess is that you have the negative side of your internal speaker wired to PC board ground.
is it?
it should not be.
it should be wired to pin 4 of your mic jack.
check that and get back to us.
LC
My new guess is that you have the negative side of your internal speaker wired to PC board ground.
is it?
it should not be.
it should be wired to pin 4 of your mic jack.
check that and get back to us.
LC
Midnight special, the pa is for public address only it's not supposed to receive through the pa Jack, but to only make it a loud speaker.
Loosecannon the negative to the speaker is soldered on board and that connects speaker negative and w5 to c52 that goes to a ground screw to the case. W5 comes from the front of the radio and is soldered to the board in where the mic plugs receive wire is soldered onto the board.
Loosecannon the negative to the speaker is soldered on board and that connects speaker negative and w5 to c52 that goes to a ground screw to the case. W5 comes from the front of the radio and is soldered to the board in where the mic plugs receive wire is soldered onto the board.
I changed all the ceramic caps leading speaker ground to chassis ground yesterday, I though maybe the problem was there but still no sound from internal speaker.
I also changed both r51 and the external speaker jack and pa jack nothing has worked yet lol I'm not sure where to go from here theres not much left stopping the speaker from working.
Ok so I just checked the speaker again and it's bad? Already? Worked fine when I tested it and no sound ever came out of the radio through it. I'm gonna try another speaker then I'll get back with what happens in a few.