Cobra 150 gtl keys up modulates then drops off about a second later. no carier no modulation.unplug the radio or turn it off wait 30 seconds try again does same thing .does anybody know what it is and if you do can you give detailed instructions what part it is and what the number location is on the pcb board.I dont have the schematic.Thanks for any help.

Most likely, you have no 'voice' signal coming from the microphone. The MODulation control did not turn itself.
Check for signal from the shielded or white wire from the mike.
A capacitor could have shorted in the modulation limiter circuit, limiting the modulation to 0%.

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.

The output stages were very poor on these radios and if it still has warranty I would contact Cobra for an upgrade or replacement....

make sure they didn't clip your mod resistor in the radio if they did soilder it back and try again.

Um... What?? This is hooked to a switch? CB radio by FCC regulations is only supposed to have a max of 4 watts total output. If you can flip it to 7 watts dead key, you are doing really good. It won't do much more then that. It sounds like its set up to run on a linear amplifier, which cannot have more then 3 watts dead key transmitting into it.

Dead key, and modulation are different. You may have a meter that only reads dead key, and won't see the modulation. This radio is probably swinging close to 15-20 watts. you need a meter that can read PEP, Peak envelope power. Cheap meters only read AVG, or average power, witch will only show your dead key.

7 watts dead key is really good for that radio.especially since stock only has 4 watts. you cannot get any higher then that without changing finals.

at 3 watt dead key, or 7 watt dead key, your modulation wattage is still swinging much higher.

Also, you will get more swing with a lower dead key any way, which is better if you want it to be loud.

Leave it alone. its probably set just right.

RV14,RV13,RV12anRV4 this will give you some tune up and modulation to.

they have a surface mount audio driver transistor. if replace with a to-220 version normally the warbling will go away. same for the 200gtl

RV12 is the modulation adjust for the 150. Check with cbtricks.com for physical location.

audio is clipping due to improper setting amount of modulation. should be set at 95% retune it ...docs cb shop ny

You never want to clip modulation limiters All youll get is a overmodulated splatterbox and it will sound like crap!! Try cbtricks.com and youll find the tuning info for that radio...Chia