Had the ext speaker jack resoldered on my connex 3400 and now I’m getting no modulation and buzzing noise when I talk into the mic. I can receive just fine. Everything I’ve read has me leaning towards the echo board. Does that sound right? New to the cb game but wanting to learn. Also if it is the echo board what can I replace mine with. Seems that parts for the 3400hp are hard to come by
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No modulation
- Thread starter Npollman
- Start date
Shadetree Mechanic
Delaware Base Station 808
Welcome to WWDX! Did it work before the socket was fixed? You might be able to bypass the echo board to test transmit function. I am not familiar with this radio, maybe someone who is will chime in.
Chris
Chris
Thanks! Yeah it worked before I pulled the cb our to fix the socket. Not sure if it’s related at all but would like to get it back going again. My cobra 29 is nice but it’s no connex
Shadetree Mechanic
Delaware Base Station 808
Maybe a blob of solder fell on the board when you fixed the socket? Might want to double check your work.
A bright light and a magnifier are a big help for finding this kind of problem.
A fault that never appeared until a different problem gets fixed is probably related to what was done in the radio.
A coincidence like this is incredibly rare. An accidental "new" fault is kinda common, even after a simple repair like the speaker socket. There is a jumper wire on the component side of the board that passes directly in front of the big modulator transistor at the rear corner of the radio just forward from the speaker socket. This jumper wire carries speaker audio from the speaker amplifier chip to the external-speaker socket. A very close look at this jumper wire and at the foil pad at each end of it may reveal the problem.
73
A fault that never appeared until a different problem gets fixed is probably related to what was done in the radio.
A coincidence like this is incredibly rare. An accidental "new" fault is kinda common, even after a simple repair like the speaker socket. There is a jumper wire on the component side of the board that passes directly in front of the big modulator transistor at the rear corner of the radio just forward from the speaker socket. This jumper wire carries speaker audio from the speaker amplifier chip to the external-speaker socket. A very close look at this jumper wire and at the foil pad at each end of it may reveal the problem.
73
Doesn't this radio have a roger beep? If it does and it still works you know the problem is in front of that and the echo board is in front of the roger beep. Audio goes through this board even when it's off. Check the plug in connections on the echo board. One may not be fully seated or have a bad connection from moving the radios wiring harness while working on it. If the roger beep does not work, the issue is in the later stages of the modulator. Is the AM carrier level normal? If it is higher than normal, you may have shorted out the series pass modulator.
Another helpful thing to know is where do you hear the buzzing sound coming from when you transmit? Is it through another receiver that you're listening on or is it coming from this radios speaker? If it is coming from this radios speaker, that is almost a sure sign the trouble is related to the speaker jack repair.
Another helpful thing to know is where do you hear the buzzing sound coming from when you transmit? Is it through another receiver that you're listening on or is it coming from this radios speaker? If it is coming from this radios speaker, that is almost a sure sign the trouble is related to the speaker jack repair.