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Pro 640e no tx audio mic ok just a flat carrier rx ok on am-ssb front meters work fine swr reading ok no tx modulation on ssb or am audio amp ic ok no pa? audio

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How are you testing the audio out?
Are you using another radio?
If so, are you REALLY sure the other radio is ok?
If the other radio is ok, how do you know the mic is ok? have you tested it with another radio?
If the mic is ok, id have a look at the mic socket to check that all the pins are still there. Then open the radio up and check the socket is still connected to the main board.

Let me know how you get on..
M3ODQ

Posted on Feb 02, 2009

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What is Dead Key on a CB Radio?


Deadkey is slang it is CW or Carrier wave which is RF power produced before modulation/audio is mixed in which stimulates PEP wattage slang being SWING WATTS. A Watt Meter is used to measure it which is often a combination device Wattage/SWR/Modulation meter.

May 08, 2013 | Galaxy Radios DX-949 CB Mob ssb Swr...

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Radio quits after 15-30 seconds


without more detailed info, quick suggestion - thermal fault, if all TX audio works when in this fault condition, it may be fair to assume audio IC is ok and check electrolytic capacitors and dry joints.

Nov 28, 2011 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

NO AUDIO / NO TX


OK bare with me now i have no idea of your knowledge level with CB/ SSB radios.
Lets make sure our setting on radio face is correct before we decide this is an mechanical problem.
Set the following
  • Volume knob 12 o'clock
  • Dynamike knob 12 o'clock
  • Squelch full counter clockwise
  • Rf gain full clockwise
  • Select S/RF position on the SWR/CAL switch
  • Select AM position on the USB/AM/LSB switch
  • Select CB on the CB/PA switch
Now there will be some critics with opinions on the next instructions. Place a small screwdriver or test lead from a multimeter in center conductor of antenna jack listen for onair noise or radios operators to verify RX is working. Now remove the antenna/screwdrive/testlead. Then key mic just long enough to notice if the meter is swinging do not hold the mic button long this can damage the final. I tell you to do it this way rather that connected to your antenna system so we can eliminate the question if it is you antenna sytem or the radio.
If the LSB or USB was selected when you keyed the mic you would see no meter movement this is due to the lack of a deadkey or carrier for SSB which is a much more efficient method of transmitting on AM.
There are few things that affected the rx and tx together.

Aug 16, 2011 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer

Galaxy DX 959. SSB doesn't seem to work. The power meter needle moves in AM but not in SSB. I tried adjusting the bias between test points 7 & 9 to 50 mA via VR12, but can only get it down to 90...


on ssyou are some what familiar with working on radio's. just make sure before you pull your hair out aligning the radio that you made sure it definitely is not tx on ssb. b the.Mic gain will increase the modulation. it could just be a meter issue. confirm this by having some one on another radio on ssb the same channel listen for you. if he cannot hear you then the ssb is blown out.sounds likelike

Jun 19, 2011 | Galaxy Radios DX-959 40-Channels Base CB...

1 Answer

Cobra 29, no rx, no tx, pa dose not work, good mic, good ext. speaker, mic. gain all the way up, and you can see meter in face neddle moveing it rec. just no audio at alland no modulation.


Not sure which model you have as there are at least 13 cobra 29's. I am using the LTD as an example. You say good mic? Is it made for this model? If it is good then I would have to say the final audio stage is not working. The TA72222AP is the IC that is the final audio amplifier. Check pin 1 of the TA72222AP ic for 12 volts. If 12 volts is present then replace the audio IC TA72222AP. If 12 volts is not present then you have power supply problems that are internal. The conclusion I have made is based on no rx audio, ( could have been the jack at the pa and ext spkr) but you say they don't work either, also no meter movement during modulation check (that does not need a spkr to make the meter move) so yes I'm 99.99% sure its the final audio stage is a bad. If your model is not the LTD then the IC could be different but still the same audio final is bad. Replace the part which should be fairly inexpensive. If it uses a metal heat sink be sure to apply heat sink grease when installing new part.

Feb 26, 2011 | Cobra 29 LTD CB Radio

1 Answer

Magnum 257 HP , no problem at all on AM or FM , modulation OK. SSB is distorted with low modulation , higher modulation seems to make it better but not consistantly . Used dummy load , BK CB tester w/2...


Nope, your not the only one. Poor power regulation internally and maybe check your antenna swr. Higher wattage with even 1.9:1 i have seen exports have issues.. and then the magnum with there alc mod (compressor) on the op amp..

Dec 18, 2010 | Magnum 257 CB Radio

2 Answers

Cobra 18 wx st receives-wont transmit


Take the cover off, flip it over solder side up, check all solder joints for cracks, cold solder joints, check the safety diode where it comes in the radio, before I go further, can you pick up the weather channel?...Does the PA work?...need to check the pre-driver and finals,audio chip, hook up the power meter using a coax three foot jumper from the output from radio to the input of the watt meter, then the antenna, first check the SWR, on the scale on the meter to cal/swr mode,adjust it to spec, then while still keyed down turn the dial to SWR,if it is the safe range your ok,then turn the Dial to 10 or 20 watt scale and key the mic. Does it have any wattage? If not suspect the finals, they are located on the back rail, if it does have RF then its the audio chip, its located on the right side rail facing you,closest to you.remove it and replace it with same ....hope this helps....

May 21, 2010 | Cobra 18 WX ST 40-Channels Base CB Radio

1 Answer

I have a cobra 25 ltd and when i key the mic the gauge of the db barley goes up. is something wrong ? also the gauge says its measuring tx power what does that actually mean/ do


TX means transmit. There are 3 settings for the meter. The top one is to measure your TX/RX that's transmit and receive. CAL is to calibrate the meter to check your SWR.

Reasons your needle may not be moving much when you key while on TX/RX. The dynamic is probably all the way down. That is your mic gain. If you turn that up when you talk the needle will swing more. If the radio is stock and not modded, you can turn this all the way up and leave it.

Also there could be something wrong with the mic. If people can hear you then its not the mic.

If people can hear you fine when you transmit, it may just be a bad meter. Not a big problem, you will just need an external meter to make sure you swr is not high.this is important because if it is over 1.5 you run the risk of blowing the final transistor.

Oct 11, 2009 | Cobra 29 LTD CB Radio

2 Answers

When i key up the mike the tx/rx light and the ant


your swr setting are off wack fix your swr

Oct 02, 2009 | Cobra 29 LTD CB Radio

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