Need Help With Cobra 29 Mod

[ChromeCobra]

Hi I'm new here and would like to do this mod to my Cobra 29 LTD Chrome AM/FM Cb. I can't find the jumper it is talking about in the photo.

 

[ChromeCobra]

Here is the image

 

[AudioShockwav]

Here is the image

I apologize, I can't make out the picture it's blurry.
NPC mod maybe?
Can you link to where you found the image?

73
Jeff

 

[ChromeCobra]

Let me post the original post

 

[ChromeCobra]

Here is the original post https://www.worldwidedx.com/threads/sweet-easy-variable-dead-key-for-cobra-29s.223406/ the jumper I am talking about is jp32 I have a old cobra 29 that doesnt work jp32 is the jumper he is talking about removing but it isn't in the radio I'm trying to do the mod to

 

[AudioShockwav]

Here is the original post https://www.worldwidedx.com/threads/sweet-easy-variable-dead-key-for-cobra-29s.223406/ the jumper I am talking about is jp32 I have a old cobra 29 that doesnt work jp32 is the jumper he is talking about removing but it isn't in the radio I'm trying to do the mod to

Ah
Yes now I get it.
I have no idea what the new AM FM Cobra radios are using for the board.
Give it a minute and see if anyone here has played with the new model.
Posting pictures of the board in your radio may help.
And welcome to the group.

73
Jeff

 

[ChromeCobra]

I just found jp32 in my radio but I don't know if it does the same thing as it does in the old radios thank you so much for the help here is the picture

 

[ChromeCobra]

I followed the trace and the left side of my jp32 connects to tr22

 

[ChromeCobra]

The point of my pen is the left side of jp32

 

[ChromeCobra]

Quick question the mod in question is just changing the voltage going to the driver to in turn change the dead key I'm still learning so if you laugh I understand I just love radios and would like to learn more you know not just doing a mod and not understanding what it's doing if you understand me but if that's what it does could we get the said voltage elsewhere?

 

[AudioShockwav]

Does anyone have one of these new Cobra's that have done the variable carrier mod?

73
Jeff

 

[nomadradio]

is just changing the voltage going to the driver to in turn change the dead key

Yep. A fixed resistor with an electrolytic capacitor in parallel with it permits the full peak audio voltage to reach the driver while holding the carrier down. A NPN transistor in place of the resistor makes it variable. I know we put a carrier control into one or another new radio like that. Had to cut a foil trace to interrupt the modulated B+ to the driver's collector circuit. Had to add a bypass cap, since the driver "shared" the one on the final's collector choke.

Might not be the one you have but I'll check our photo archive.

73