Question about Cobra 148 GTL 120-Channels Base CB Radio

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148NW ST No TX AM or SSB

Hiyas. Got a radio here with a problem: radio powers up and receives fine, but when mic is keyed, S/RF meter swings to the right, then drops back to the left. No TX, no modulation. Any idea as to what can cause this? Thanks

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Finals need to be replaced, as they are fried,, hence no output,,and if you are lucky you haven't fried the pre-amp as yet....as the pre amp is REAL EXPENSIVE....so stop keying it up

Posted on Jul 30, 2007

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Posted on Jan 02, 2017

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1 Answer

SSB dead key & TX frequency problems


Check C-144, c-149, c-153, c-154 using an ESR meter.

Dec 23, 2011 | Galaxy Radios DX-2547 40-Channels Base CB...

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

2 Answers

Cobra 2000 with a d 104 mic and a palomor tx100 bi linear amp...how can if possible make the amp key up with less than one watt on the ssb side..Radio has a 4 watt dead key on am and i have ajusted the...


Hi, my name is John. Adjust the radio to key 1 watt, then switch to SSB on radio,then switch to SSB on amp, key down and adjust to 1 watt on amp. enjoy !!!!!! ...hope this was very helpful....

Aug 31, 2010 | Cobra 148 GTL 120-Channels Base 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

2 Answers

How to adjust frequency on transmit??? Galaxy


hELLO THERE
hERE IS SOME MODIFICATIONS FOR THIS RADIO
Galaxy Mods DX 2527 - VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR11...Driver Bias, VR12...SSB ALC, VR13...Hi Power, VR14...AMC, VR15...AM Low Power, VR16...SSB Low Power, VC 1....10.240, VC 2....10.240. DX 2517- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5....FM Deviation, VR 6....SSB Carrier Balance, VR 7....TX Offset, VR 8....CW Beep Level, VR 9....RF Meter, VR10...Final Bias, VR11...Final Bias, VR12...Driver Bias, VR13...SSB ALC, VR14...AM/FM High Power, VR15...AM Modulation Meter, VR16...AM Modulation, VR17...SSB Power, VR18...AM/FM Low Power, VR601..13.8 Volt Power Supply. DX 22B- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR11...Driver Bias, VR12...SSB ALC, VR13...High Power, VR14...AMC, VR15...AM Low Power, VR16...SSB Low Power, VR21...TX Offset, VC 1....10.240, VC 2....10.240. DX 11B- VR 1....AM/FM S-Meter, VR 2....SSB/CW S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR10...Final Bias, VR11...Driver Bias, VR12...SSB ALC, VR13...AM/FM High Power, VR14...AM Modulation, VR16...CW Tone Level, VR20...Final Bias, VR21...TX Offset, VR601..13.8 Volt Power Supply, VR803..AM/FM Low Power. DX 77HML, DX 88HL, and DX 99V- VR 1....AM/FM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 7....SSB Carrier Balance, VR 8....RF Meter, VR10...Final Bias, VR11...Driver Bias, VR12...SSB ALC, VR13...AM/FM High Power, VR14...AM Modulation, VR16...AM/FM Low Power, VR20...Final Bias, VR21...TX Offset.
Unmarked VR in R189..AM/FM Medium Power for DX 77HML only. DX 33HML, DX 44V, DX 55V, DX 66V, and DX 73V- VR 1....AM/FM S-Meter, VR 4....AM/FM Squelch Range, VR 5.....FM Deviation, VR 8....RF Meter, VR12...Low Power AM Modulation, VR13...AM/FM High Power, VR14...High Power AM Modulation, VR16...AM/FM Low Power.
Unmarked VR in R188..AM/FM Medium Power (DX 33HML only)
Unmarked VR in C139..Med Power AM modulation (DX 33HML only) DX 949,DX 959- VR 1....AM S-Meter, VR 2....SSB S-Meter, VR 3....SSB Squelch Range, VR 4....AM Squelch Range, VR 6.....SSB Carrier Balance, VR 7....TX Offset, VR 9....RF Meter, VR10...Final Bias, VR12...Driver Bias, VR13...SSB ALC, VR14...AM High Power, VR15...AM Modulation Meter, VR16...AM Modulation, VR17...SSB Power, VR18...AM Low Power, VC1....10.240. DX 2517 and DX 2527-
Symptom:Buzzing or motorboating sound in either the transmit or receive.
Problem: TR602 is oscillating
Cure: Replace C602 with a .01uF cap {Cap is located in the power supply board}.
RG 66,99,DX2517 Replace Q54 2SB754 60watt 7A with a higher power 2SB817 100 Watt 12A. Derating of this component will cool operation, provide better voltage stability,decrease wobble, allow voltage increase to 14.5 volts comfortably. (replace 10 volt caps in this section of the radio to a minimum of 16 volts before increasing supply voltage to this level)and provide faster swing rise time, Replace Q37 2SA473 to a 2SA1012-0 or ECG153 this will improve the clarity and volume of the modulation and it will also run a lot cooler.

Nov 12, 2009 | Galaxy Radios DX-949 40-Channels Base CB...

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

Cb is Keying Down instead of keying up when trying to talk


if you are transmitting fine Don't worry about the meter. Get an external SWR meter, they are better anyway.

Also, make sure the the switch next to the meter is all the way up on s/rf setting. thats for signal power and receive strength.

Aug 30, 2009 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

When mic is keyed, TX light illuminates but power meter does not


make sure your s/rf switch is in the right place on the radio is the most common problem i have found

Feb 05, 2009 | Radio Shack TRC-447 CB Radio

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