Cobra 29 LTD Chrome No Transmit Help

[HavaV10]

I have a 2007 model 29 LTD Chrome that's in great shape, but it will not transmit. I have checked the driver and final and a few of the 2SC945 transistors and all have tested good. Also recapped almost all the electrolytics. The PA and talkback have audio so I don't think the audio IC is at fault. I have 13.8V at both ceramic disc caps C142 and C143. There is also receive but it is making a very faint squeal in the white noise. I don't have a schematic or high end test equipment. Just trying to fix this radio the poormans way. Also checked for cold solder joints and couldn't find any. I'm at a stand still here. Would someone might be able to help me out fixing this radio? I'm sure I have over looked something and still have a bad component somewhere on the board but I just don't know where to look for it. Thanks for any help.

 

[nomadradio]

Um, what tools do you have on hand?

I'll guess that an oscilloscope is not on the list.

How about a second radio to listen and see if any weak signal comes out of the Cobra 29 when you transmit?

There is also receive but it is making a very faint squeal

Does that mean you can hear channel noise, and people talking? You're not very specific about what the receive side will do or won't do.

A dummy load is useful, but not absolutely necessary if you have a proper antenna.

A frequency counter can be handy.

A Volts-Ohms-Amps multimeter can also be useful.

Are you sure the power pack you're using is delivering full DC operating voltage to the radio?

Have you ever seen this radio work before, or was it this way when you first encountered it?

Is there any chance that somebody else already tried to fix this radio? If so, it's incredibly common for new faults to be introduced to the radio during a failed repair attempt.

A radio that was working until it had "just one" failure in it will be a lot more straightforward to get working that a radio that has had several sets of fingers in it since it last worked properly.

73

 

[HavaV10]

Um, what tools do you have on hand?

I'll guess that an oscilloscope is not on the list.

How about a second radio to listen and see if any weak signal comes out of the Cobra 29 when you transmit?


Does that mean you can hear channel noise, and people talking? You're not very specific about what the receive side will do or won't do.

A dummy load is useful, but not absolutely necessary if you have a proper antenna.

A frequency counter can be handy.

A Volts-Ohms-Amps multimeter can also be useful.

Are you sure the power pack you're using is delivering full DC operating voltage to the radio?

Have you ever seen this radio work before, or was it this way when you first encountered it?

Is there any chance that somebody else already tried to fix this radio? If so, it's incredibly common for new faults to be introduced to the radio during a failed repair attempt.

A radio that was working until it had "just one" failure in it will be a lot more straightforward to get working that a radio that has had several sets of fingers in it since it last worked properly.

73

no one has been in the radio. Transmit is dead. I have tried everything. Replaced all electrolytic caps, tested some of the C945 transistors and a few diodes. No luck. Yeah I'm listening in on another radio when keying the mic. Nothing heard. Red/Green LED's do work. PA works, talkback works. Used freeze spray and pushed on the pcb board with little force checking for cold solder joints.