20 Most Recent Cobra 25 LTD 40-Channels Base CB Radio - Page 7 Questions & Answers

I recall problems grounding the antenna on those kw's. May want to try a no ground antenna. Also the stock coax that comes with the truck sometimes gets broken or pinched. Go to a good shop, replace the cheap coax and grount the antennas.

the easiest thing to check first is the mic..........if the mic is broken cobras wont receive or transmit
hope this helps.......good luck!

so what your asking then if you can increase the signal strength so I goes farther? If so then you can go to any radio shack and buy a signal booster that hooks up through the anntena line.

I think this is a double post,, am I right Freddy??? Mechanic

Hello richf, With out a complete rundown of what you have, I'm sort of guessing here, but I'd say offhand that you are not using a base antenna. Most "full waves" are usually mobile fiberglass antennas. If this the case, Get the antenna above the metal siding, you might be getting a "reflection" back from the metal skin and causing a extreme high SWR which will cause damage to your radio, from a short period of talking. Either go higher up to clear the siding or put up a mast pipe and order or buy an Antron 1/2 wave base antenna. Those are a 3 piece fiberglass base ant. that is tunable for different situations. Run roughly about $50.00 but solves so many problems,,,Let me know more info and I'll try to help the best I can,,, Mechanic

Hello Darren, Yes it sounds like the mic is wired bass ackwards,,! A cobra 25 mic wiring is
PIN #1- Shield or ground wire
PIN#2- Audio or Transmit modulation
PIN #3- Transmit or Dead Key
PIN #4- Receive Audio.
When your keying the mic, the RX wires are being connected to make the RX work,,,
*** Let me know how you get along with it. Either buy a new mic wired for your radio or you or someone comfortable with soldering needs to resolder the correct wires back on the mic plug,,,Like I said, let me know and have a great day,, Mechanic is back quiet!

Assuming that you've tried another mike, the problem may lie in the speech amplifier circuit within the radio, something that will require someone with technical knowledge to repair.

No!

On the YD1022 the pinout is: Corresponding pins on the TA7222 :

1,5 & 6 are ground 3, 7 & 8
2 is audio input 4
3 is feedback 6
4 grounds through a capacitor for frequency compensation 5
7 & 8 are audio output 9
9 & 10 are +12VDC VCC 1

The TA7222 also uses pin 10 for feedback & freq. comp. The circuits are very different & would need to be redesigned to interchange these chips.

Not really enough info to help you, but you MUST check the SWR of your antenna system. I've seen many cases where the antenna studs were incorrectly installed, shorting the antennas to ground. Also, make sure the Dynamike control on the CB radio is turned fully clockwise.

Likely cause id the audio output circuit, centered on the TA7222AP integrated circuit.

Sounds like a "cold" or broken solder connection on the PC board.

Unless your using a Bird Wattmeter with proper frequency plugs your not seeing a true reading of power output. The radio manufacture presets the power output to a max. of 5 watts.

The Cobra 25 requires the mic to be working for any sound to come out. My suggestion is that you first try a new mic. If this doesn't work, look real close at the board on the soldered side ( around the if section, thats the area that right under the waxed area on the component side of the board ) for cold solder joints ( broken lead solder) You may need a magnifing glass. Good Luck
Ed
NC Electronic
Mills, Wyoming

Hi,

There are only a couple of components that could cause the fuse to blow. They are:
1. Reverse protection diode (D23)
2. filter capacitor (C123)
3. Outputs (TR14 & 15)
4. Audio Amp (IC4)
5. Zener Diodes (D22 & 19)
6. the fuse itself (it should be 2 Amps

Hope this be of help/idea. Pls post back how things turned up or should you need additional information.

Good luck and kind regards.

Thank you for using FIXYA.

I have the identical model and also had the same problem. I took it in to an appliance repair and they found a problem with the output circut something about a burnt transistor is what they said. I had them replace it and has been working fine since. Hope this helps.

First, is the radio new? As long as the mic, antenna, and coax work properly with another cb radio, I would start with two areas:

1. make usre the PA/CB Switch is set to CB. I have seen many people accidentally bump the switch to PA and not know it. I have done it myself.

2. Turn you Squelch all the way counter-clockwise and your RF Gain clockwise.

If these make no difference, please reply with a comment so we can further assist you.

have you checked your swr?

does it have an rf gain on it? if so turn it wide open

A manual link is at the bottom of this entry. Troubleshoot the problems you've described: Meter Not Working: The needle moving slightly to the right when you key the mic could be due to incorrect calibration. Make sure to recalibrate the meter according to the manual instructions. If you calibrated it differently, that might cause the needle to go against the right side of the meter. Recalibrating the meter should resolve this issue. Meter Light Problems: If the meter light isn't working, consider replacing the LED. Sometimes, a burnt signal meter light can occur. Replacing the LED should fix this. SWR Meter Not Working: Incorrect SWR calibration or bumping the calibrated knob might cause the SWR meter to malfunction. To check the SWR meter: Turn on the SWR calibrate knob until it keys up all the way at the end. Switch to SWR mode and key the mic. If the needle barely moves, turn down the Dynamike knob. Finally, switch back to S/RF mode. No Receiving Audio: If you're not receiving audio, check the following: Ensure the squelch knob is adjusted correctly. Start with the knob counterclockwise and turn it slowly clockwise until white noise stops. Verify that the microphone is working properly. You can try a different mic to rule out any mic-related issues. Make sure the radio is on the correct channel for transmitting and receiving. ========================================== Calibrating the SWR (Standing Wave Ratio) meter on your Cobra Classic 29zLtd CB radio is essential for optimal antenna performance. Follow these steps to calibrate it properly: Prepare the Setup: Park your vehicle at least 20 feet away from trees and buildings. Close all doors, hood, and trunk. Choose the Channel: Select the channel you want to check. It's recommended to test on channels 1, 20, and 40. SWR Calibration: On the radio, press the SWR/CAL button until the display shows "CAL." While pressing the transmit button on the microphone, turn the SWR CAL knob (the last knob on the right) until the meter needle aligns with the "CAL" mark. Release the transmit button. Switch to SWR Mode: Push the SWR/CAL button again until the display shows "SWR." Read the SWR: Press the transmit button on the microphone. Observe the SWR reading on the top scale of the meter. Ideally, the SWR should be below 3. Lower values are better. Remember that SWR is a measure of antenna performance, and poor SWR can be caused by the antenna, antenna cable, or installation. Adjust the antenna length to achieve similar SWR readings on channels 1 and 40 while keeping it below 3. Most antennas are adjustable; refer to the manufacturer's instructions for specific adjustments. cobra-29ltdclassic-cb-radio-user-manual.pdf (roadtrucker.com) MANUAL

See page 11 of user manual MRHH600B_ENG_MANL_REV_01522_NO_SEATOW.pdf (shopify.com)