It's the older superstar 3900. The schematics were posted above earlier. thanks

 

I would replace C145 and C146. Is this a down under radio? Does this radio require that the mic be plugged in to hear speaker? I heard this once before. I have never seen this. Why do they do that? I wouldn't give up on it, if everything else works. I like 10 and 11 meters.

 

they use electronic switching to not pay the price of a relay. the cobra 19 used electronic switching. I still say poen up the microphone and see if the contacts for recieve are closing before the transmit contacts open.

 

Thanks for the replies. I am not sure if the rec is cutoff when mic is unpluged i will check. Also i drive a truck and listen
to 11 meters everyday. Have been for 30 yrs. Do not appreciate #12 and the attitude in the above post. Thanks alot.

 

You may "drive a truck & listen to 11m",but that has very little to do with a "10 m" Radio.
If you are transmitting on "10 m"with that Radio without having the required licence,it is in fact an illegal act in virtually every country in the world.
As you have been very cagey about the licence question,posters may be very reluctant to help you further.

It's not "attitude" it is the fact that possibly helping you do something illegal would violate the spirit,if not the letter of the forum "terms of service",as published on this site.

 

Who said i was not licensed ?

 

You should check out alfacliff's suggestions first.

 

I did the radio recieve is still on with mic unplugged. Thanks

 

These radios have the TA7222 amp powered up on transmit or receive. Muting for transmit is applied at pin 5.
C145 may be leaky causing a DC voltage on the speaker but it could be caused in other places.
I see a lot of these low cost mobile radios and their major problem is solder connections or some tweaker has been into it.

 

These radios have the TA7222 amp powered up on transmit or receive. Muting for transmit is applied at pin 5.
C145 may be leaky causing a DC voltage on the speaker but it could be caused in other places.
I see a lot of these low cost mobile radios and their major problem is solder connections or some tweaker has been into it.

 

I Noticed pin 3 was open which is the muting pin. I tried a cap to ground on pin 3 with no effect . I dont guess a cap could be added at pin 5 on transmit correct ?

 

You are 100 % correct. Cheap design poor solder, the design flaw is almost impossible to fix. It would take someone on a very higher level than I . Maybe someone on a higher level will chime in. When the talkback is on the nasty pop is gone, if i could
just figure out how to stop the talkback to not be audible is the trick. Alan @ kobg.com hit the nail on the head, it should have been biased off rather than switched off Bad Design. Guess i am runnin in circles lol!! I had the audio ic replaced with a 3.5 watt Kemo audio amp module, bingo the pop was gone. Then the recieve was effected tremendously, very high pitch tinny sound
not a volume problem but a tone quality issue, sounded like off frequency but it wasn't. Keep prayin......

 

As for your question.......Pin5 has a cap on it.
Generally talkback is desirable. It allows you to hear if the microphone is breaking up.
If you were to remove D80 then talkback would be on all the time. TR36 supplies power to the transmit circuits while TR38 is used to supply power to the receive circuits. If you were to get power from the collector of TR36 with a resistor to the muting pin3 on the TA7222, you may get the muting you desire.
Or you may try replacing some of the capacitors connected to the TA7222, one of them may be defective and causing the problem.

 

As for your question.......Pin5 has a cap on it.
Generally talkback is desirable. It allows you to hear if the microphone is breaking up.
If you were to remove D80 then talkback would be on all the time. TR36 supplies power to the transmit circuits while TR38 is used to supply power to the receive circuits. If you were to get power from the collector of TR36 with a resistor to the muting pin3 on the TA7222, you may get the muting you desire.
Or you may try replacing some of the capacitors connected to the TA7222, one of them may be defective and causing the problem.

I agree,-some positive volts on pin 3 should mute the thing OK,as pointed out in the datasheet.
http://pdf.datasheetcatalog.com/datasheets/400/502310_DS.pdf
hardrock's original suggestion that it needed to be 'biased off" is very close to correct.

The question is,why don't these radios all have this problem?
Or maybe they do?

 

They all have this problem up until 2006 when they changed to the tda2003 ic.

 

What value resistor should be used off tr-36 to pin 3 ? I don't want to smoke the ic....

 

I would try a 1k and a .1ufd cap on pin 3

 

They all have this problem up until 2006 when they changed to the tda2003 ic.

I haven't known this popping to be common problem and I haven't seen the tda2003 used on these Ranger boards yet.

 

I was told this by radioshopsupply in ca. I have 3 of the radios they all do it. I will try the res/cap on
pin 3. thanks

 

Perhaps the popping is something I just haven't noticed. I'll check it out Tuesday when I return to the bench.