Cobra 200 GTL-DX Disable Talkback
The Cobra 200 GTL-DX has a built-in talkback function. Some models allow switching this function on or off as desired, others have the ability to adjust the volume. This particular version of the Cobra 200 GTL-DX has a fixed volume, which the customer doesn’t want.
Luckily, the service manual has details for a mod to adjust the preset level of the talkback function. The mod simply comprises of changing the value of a single resistor, in this case R109. The resistor is a 33K ohm SMD device, and located in a quite densly populated area of the PCB.
If the talkback function is to be maintained but a higher or lower volume is required, it’s simply a matter of changing this resistor to one of a different value.
The talkback audio path is taken from the path that runs from the ALC switch to the echo processor, this is then fed via a few more components into the audio amp.
By removing the resistor we are simply breaking the path to the audio amp, thus completely muting and disabling the talkbak circuit.
Hopefully you will appreciate just how tiny and closely spaced these components are and the extreme dexterity required to remove, or indeed to replace, these tiny modern SMD components.