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Cobra 75 Not Receiving!

Portager

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Messages
1,506
Location
Silverado
On the last off road trip my Cobra 75 CB was transmitting but not receiving. No sound comes out and the squelch has no affect. I've tried turning the volume up and down and every channel but I get no sound output and no Rx power on the LCD display. Can anyone think of something simple that might be causing the problem?

I called Cobra and I have to send it to Chicago and hope I get it back before Cleghorn. I tried the Warranty Service Center in Downey CA. (14.5 miles from my work) but they don’t service the Cobra 75.
 

Portager

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Messages
1,506
Location
Silverado
To the best of my knowledge, there is no RF gain adjustment on the Cobra 75. I searched the manual and nothing showed up.

It was working fine the run before, so the only thing I can think of is the people at the carwash might have change something, but I can't think of what could cause no sound (other than turning the volume all the way down).

Maybe the "Soundtracker" feature is over achieving?
 

06 H3

a.k.a. "The Jackal"
Messages
9,350
Location
Meridian, ID
I have been doing some more searching around. I would hook up an external speaker if its easily accessible to get to. I would also check all connections, kinked wires and other little things can mess with reception. I would start with the external speaker because that seems easiest.
 

Portager

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Messages
1,506
Location
Silverado
Yea, sounds like the same problem. When I called Cobra they just said send it back. Sounds like they knew it was bad. Since it is still under warranty, I'll return it.
 

alrock

El Diablo
Staff member
Messages
10,442
Location
Scottsdale
When you remove the cb take the time to go over your system, most importantly your antenna cable. Perhaps even put an SWR meter on before you remove to see if there are any obvious ground issues. A cut cable could create a ground problem which would blow out that speaker. Trust me, this comes from experience with this radio :emb:. My cable had a small tear which allowed the metal of the cable to hit the body of the truck. I don't think that tear always hit the body, meaning the issue would be intermittent and would not always show on an SWR meter.

I also replaced a cable when in Moab as my windshield installer "helped" me by rerouting the cable which created a sharp bend and ending up breaking the cable. I was coming across garbled to others (and no Scotch was involved.)
 

Portager

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Messages
1,506
Location
Silverado
The last time the CG was working I noticed that I was getting a loud noise when the doors locked and unlocked. I wonder if that is what damaged the speaker?

Maybe I need to change where I'm getting my power from or put an isolator on the power line?
 

Portager

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Messages
1,506
Location
Silverado
I talked to an Electrical Engineer at my work and he thinks the noise is due to electro-magnetic emissions from the door lock solenoids which is picked up by the CB radio. This may be impossible to filter out without degrading the reception. we agreed that the way to isolate the problem is to power the Cobra 75 from an external power source and see if the noise goes away or not.
 
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