Swapped GTX330 transponder for 330ES and now have static in headset

[jd21476]

I bought a used 330ES transponder and had an avionics shop swap my GTX330 for the 330ES. I now have an annoying static in my headset and I know its from the transponder because when I turn it off the static stops. The shop claims they simply pulled the old and slid in the new and then ran a wire to my GPS so it would not cause the static. Any options?

 

[Jesse Saint]

Is it just static or is there a pulse to it?

 

[jd21476]

It seems to be static

 

[Elvin Wilkerson]

I would have the grounds rechecked at both ends of the antenna coax and recheck the antenna grounding.