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Re: new power chip
To my knowledge on a Cobra 29 board, replacing TR14 (2SC2029) with a 2SC1969 is supposed to improve/increase the TX power output. Additionally however, L12, 13 & 14 must also be adjusted while the 29 is hooked up to a dummy load/watt meter. Should you wish to try for experimental purposes only:
Modulation improvement - adjust VR4 to desired level or cut D11or max talkpower remove TR18 .
replace TR14 with 2SC1307 (or 2SC1969).
Hope this be of initial help/idea. Pls post back how things turned up or should you need additional information.
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is mic plugged into radio? put oin another 4 pin cobra mic and see if it still happens.make sure your squelch is wide open and rf gain is also.If you still have the problem it could be several things. Final , main IC, or audio chip.
You can try to replace the final transistor and see if that helps. Do you have receive? Plug an external speaker into the PA and switch the CB to PA and key down. If you hear yourself that eliminates the voice chip. Always make sure you check your SWR and maintain below 1:1.5 no higher than 2. Any further questions of comments let me know.
Just because the chip is warm doesn't mean it's bad, especially if it seems to work fine otherwise. Do however make sure that the device is properly heatsinked, and inspect the work done in the process of any modifications. If for some reason the device is self-oscillating it could do so at a frequency above hearing thereby going unnoticed. That will cause the device to overheat, and also make modulation weak and the RF to splatter out of band. You'll have lots of power on the RF wattmeter, but people can barely hear you if that's the case.