Cobra 25, 29 Uniden PC 66, 68, 78 Talkback Mod

This is a easy $1 mod to add talkback to your CB Radio.
This will work for the following radios with no problems.

Cobra 25
Cobra29
Uniden 66
Uniden 68
Uniden 76
Uniden 78
and many more.

All you need is a simple resistor added to the bottom of the board, near the Ext and Pa speaker jacks.

Find the 2 solder points, closest to the rear of the radio, directly above the EXT and Pa jacks.
These are going to be the Negative or Ground side for the audio.

Solder a 1/4 or 1/2 watt resistor between these two solder points. Make sure that the resistor itself does not short out anything on the board or touch anything else. You can wrap it in tape, heat shrink or just keep it lifted slightly above the board.




Use a 100-500 ohm resistor.
The Lower the resistance is, the Louder it will be.
A 100 ohm will be Louder than a 470 ohm.
I like to use a 220 for most mics, or a 470 for good power mics.
You can also wire up a 1K variable pot to adjust the volume level.
You can also use a switch to turn it on/off, just wire it in series.
Ive used the Norm/Ch9/Ch19 switch as a Off/Low/Hi with 2 resistors, to make it adjustable for different mics or volume levels.


Thats it! Just 2 solder points for basic talkback.

Cobra 148 GTL Audio and Power Mods.

A simple way to really increase the audio of a Cobra 148 GTL CB radio is to find R126 and jumper it. It is a 10K ohm resistor about 1" to the LEFT of the MIC jack.
Do NOT remove the TR25 Mod Limiter on this radio, as it will sound like crap later.

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To add extra channels install 2 switches in the radio, or use the HI/LOW and BRT/DIM switches on the front.
My friend wanted 2 new switches on the rear, so thats what I did with this radio.

You will need 2 SPST switches.

Find the PLL IC and find pins 10, 11 and 12 and the large Ground trace near pin 10.

Wire Switch 1 to Pin 10 (pin goes to nothing) and also to GND pad.
Wire Switch 2 to pin 11 and pin 12.
Be very careful to not use too much heat on the IC pins, and they are fragile and you can damage the PLL chip. Use a 30watt max solder pencil.