China Cobra 29 "barks" when D104 is unkeyed. Need A Fix

[Wire Weasel]

Currently playing with a newer Cobra 29 & using a D 104 TUG8. Talks fine. When I unkey the mic a loud annoying POP-Bark comes across the speaker. This noise is not transmitted out. This also happens with another mobile I have that is of completely different manufacture but what they share in common is they have the circuit style whereby you have to have a mic plugged in radio for the Receive to play. - This does not ever happen to me with any D104 & any radio that has receive without having to have a mic attached.

Does anyone know of a fix - mod for this condition? Thanks !!

 

[Robb]

Did you try to clean to contacts on the mic switch first?

 

[midnight special]

clean contacts on mike switch and make sure they are aligned and not need adjustment
,,,the wear and sometimes bend or the screws that hold the contacts together come loose and will make and break contact too fast or slow,,,

 

[Wire Weasel]

Doesn't seem to be a problem with the mic. As I stated it doesn't do this on other radios …. just radio types where you have to have a mic plugged in to activate the receive.

 

[Robb]

Do other mics - other than the D104 - make a barking sound with that radio too?
If not; then it is the D104 ptt sw.
If so; then there is a disc cap in the mic transistor switching circuit that isn't working - first blush guess.

 

[midnight special]

the receive relay contacts then is out of adjustment i would think,,,, they are not used on the radios you mention which i would guess be galaxys or connexs,,,,,,

 

[RatsoW8]

Seems like the pop on un-key is a pretty common problem with some CB's and amplified microphones. I think a disk capacitor of a few microfarads across the speaker terminals might fix it. Could be wrong but I seem to remember that from my CB days working on a Lafayette Comstat 25B using a Turner +2.

 

[Wire Weasel]

Thanks guys. I"ll try a cap across the speaker later.

I have 3 different and good working D 104 TUG8's over here at the moment. They ALL do this on this radio. NONE of them do it on any radio where you don't have to have a mic plugged in to receive …. like any galaxy. This is why I'm saying it's something about the radio's circuit design rather than any problem with the mic. Also tried a good working Turner +3 …. same thing. So it's not a mic problem although being power mics are the source of the problem so to speak. No there is no POP with a hand stock mic. But the fix should be in the radio see ??

Want I'd like to do next is convert these radios from where the way they are now, with having to have a mic plugged in to receive - into one where you do not have to have a mic plugged in …. like all the Galaxy's and many others. Anyone know how to do this? Betcha money that will cure this problem ;-)

 

[Robb]

Thanks guys. I"ll try a cap across the speaker later.

I have 3 different and good working D 104 TUG8's over here at the moment. They ALL do this on this radio. NONE of them do it on any radio where you don't have to have a mic plugged in to receive …. like any galaxy. This is why I'm saying it's something about the radio's circuit design rather than any problem with the mic. Also tried a good working Turner +3 …. same thing. So it's not a mic problem although being power mics are the source of the problem so to speak. No there is no POP with a hand stock mic. But the fix should be in the radio see ??

Want I'd like to do next is convert these radios from where the way they are now, with having to have a mic plugged in to receive - into one where you do not have to have a mic plugged in …. like all the Galaxy's and many others. Anyone know how to do this? Betcha money that will cure this problem ;-)

I know that Xit13 posted that info somewhere on the forum awhile back.

 

[darklife]

I have a Teaberry Five by Five radio that does this when not using the stock mic. After some playing around I learned it is the way the original mic button is designed. There is a momentary gap of no connection in the original button when pressed/depressed. Slowly releasing the button has no pop, but a sudden release will make the radio pop a little. Newer mic buttons have an almost instantaneous switching with no momentary gap which causes the radio to make the loud pop sound because the internal radio circuitry can't keep up with the fast transition.
Only fix I have found is to play with the speaker, either adding resistance across it to quiet (therefore forcing the volume to be turned up to compensate), or a momentary speaker disconnect using a relay/capacitor timer.