loud crackling

[jetman]

GE Superbase has had this very loud crackling in the receive. I cannot tell where it is coming from. I replaced all of the elec. caps on the top board (which is 99% if not all of the RX and audio). I will be replacing the audio IC in this radio anyway. And i can't quit get the RX to open up anymore than it is. It's not as good as I think it can be. I installed the 2sc2999c in for the RF amp, but that actualy did worse. Is there a better gain amp than a c763 (stock amp)?
Back to the popping and crackle. It happens in both CB, CB/PA, but not straight PA. But that makes since that it's not in the mic or mic amps. I've also used different mics as well. The original tested just find on mic tester as well. Would the main power cap 4700uf be causing this issue even if it's ONLY in cb and cb/pa modes? I doubt it but thought i could ask anyway.

 

[Robb]

Does the crackling go away when you disconnect the antenna/coax?

 

[pittmantree1]

does it stop at night it may be sun I get it when its hot or mid day to nightfall had me checking everything.

 

[jetman]

Yes, it's still there when I unplug the coax. You can really hear it when I turn off the ANL. But still very audiable and annoying with it on. Can't hear anything similar on my bench radio though. So it's nothing from my equipment. Happens with both AC and DC power.

 

[wavrider]

Clean all pots with DE OXIT, sounds like dirt and dust in the knobs/ also if you have any of the trimmer style caps on the board this can cause that "Crackling" sound also if they get dirty.

 

[Shockwave]

If the PA works good by itself, you can rule out the audio chip. Rather than randomly replacing one part at a time, consider using methods that can troubleshoot down to the specific component level.

Even without a schematic and test equipment, lots of problems can be found using freeze spray, a hair drier and the back of a plastic pen. The freeze spray can be used to thermally shock parts like capacitors, transistors and IC's.

With the small straw on the can of freeze spry you can hit specific components to try and isolate the problem. The hair drier will reverse the process but is not local enough to hit one part at a time so you will have to go back to the freeze spray.

Not all parts respond to temperature change and may respond to mechanical shock. Tapping individual parts with a plastic rod can pinpoint this type of problem as well as bad solder joints.

 

[Captain Kilowatt]

does it stop at night it may be sun I get it when its hot or mid day to nightfall had me checking everything.

Been in radio for 36 years and this is new to me. :blink:

 

[Captain Kilowatt]

It could be a broken or loose connection almost any where.