cobra 148 gtl motorboating on ssb and am

[kb9ikh]

i have a 148 cobra that seems to have what sounds like ac ripple in the am/ssb audio.. i have swapped out power supplies with 3 different supplies and the 148 still has the rippling sound in the audio...it's more predominate in the ssb but is there on am as well...this is with a stock cobra mike as well..thought it may have been a grounding issue but not sure.. this issue has shown upon a rci 2950 and a emperor 5010 as well.ssb and am ...i have a courier 40d that when used on dc power with these power supplies shows no sign of distortion in ssb or am........and ideas??


john

 

[mrgumby]

how many amps is the power supply

 

[kb9ikh]

between 14 and 35 amps....i have used 3 different supplies

 

[ExitThirteen]

Replace the MB3756 SIP voltage regulator. That fixes the problem in most units. Wouldn't hurt to replace all the electrolytic caps too.



~Cheers~