Cobra 2000 not transmitting, but DOES receive.

[Joshua Barry]

I have a 2000 that receives well, both in CB, and PA. I do not have any carrier on TX on AM, and no modulation on SSB. So transmit is dead. It doesnt project sound out on PA when I try either. It's just dead. But again, I can recieve sound on PA. My theory is the bad 1969 final, since none of my meters move when transmitting. Or, it could be a bad 10V cap in the audio circuit. I will perform a re-cap, and do have a replacement final on order, but would like to see if anyone may have any explanation as to the no TX.
I have tried 3 working mics, all with no change.
Any help would be greatly appreciated!

 

[nomadradio]

Does the "TX" light come on when you key the mike?

Didn't say.

Do you have another radio you can put on the same channel and a coax jumper to use as a "sniffing" antenna?

I would start with a 'scope, but if you don't have one, this would narrow down where to look next.

Do you have a voltmeter and probes? Not every fault in this radio will result in a meter reading that gives it away.

But some of them will.

73

 

[Joshua Barry]

Does the "TX" light come on when you key the mike?

Didn't say.

Do you have another radio you can put on the same channel and a coax jumper to use as a "sniffing" antenna?

I would start with a 'scope, but if you don't have one, this would narrow down where to look next.

Do you have a voltmeter and probes? Not every fault in this radio will result in a meter reading that gives it away.

But some of them will.


It does say OTA when I tx. But I dont get any emitting field strength. I've already tried sniffing for it. Nothing registers. I do have a multi meter but no scope. I've tested the final and I'm not getting nowhere near proper voltages upon TXing so that to me indicates a blown final.
When I first examined the unit before TXing I looked for burnt or visibley damaged components
I threw out a ssb carrier but nothing happened. So I switched to AM and threw out a very high carrier but no modulation. I was able to use the radios SWR meter to check my configuration and all was correct. Then nothing else after that would happen. No more AM carrier, and no movement from meters. Checked the finals, and it was supposed to be 5.6 volts AM, and 13.7 SSB. only getting like 300Mv so I'm trying it's the final

 

[sp5it]

Build RF probe, you'll find quickly where RF disappear.
Mike

 

[Unit 75]

You stated that your radio receives in PA mode. You should only receive in CB mode. Not PA mode. Look at schematic and check wiring at CB/PA switch to make sure it is first wired correctly. We can move on from there once you have fixed that problem.

 

[Chipper]

I have a 2000 that receives well, both in CB, and PA. I do not have any carrier on TX on AM, and no modulation on SSB. So transmit is dead. It doesnt project sound out on PA when I try either. It's just dead. But again, I can recieve sound on PA. My theory is the bad 1969 final, since none of my meters move when transmitting. Or, it could be a bad 10V cap in the audio circuit. I will perform a re-cap, and do have a replacement final on order, but would like to see if anyone may have any explanation as to the no TX.
I have tried 3 working mics, all with no change.
Any help would be greatly appreciated!

Following

 

[Joshua Barry]

I'm posting an update. I did discover this. More so by accident. The IC2, which is the UNIC-007 is erupted. The VCO for recieve and transmit. This could be why I'm not getting voltages at the final. And why it wont TX. I've ordered the UNIC-070. The replacement for the original 007 since its discontinued.