I have a cobra 29 classic when i got it it keyed up fine no one could hear me when i talked then all the sudden the rx/ tx light turns on when i key up

theres a shorted capacitor .. c 68 i think. thats causing this issue.
the radio will work on RX, but when you TX the lights go out and will not key up.
would have to look at a raido to see what the exact cap # is ..

if a mod has been done to the cobra 29 (all 29,s)the light will come on just find vr6 audio the radio as it comes on adjust vr6 untill it goes away,,,,always trust your watt meter(s.w.r scale)over the flashing light its really easy to do it beats paying a shop $10-$15

all functions of the radio are performed by the main IC 2816c . The frequency is controlled by this also and if it is blown you will loose your frequency and the problem that emits is in your statement.

Check speaker and plug external one in if you have it.

swap mic could be a broke wire or bad switch in handset.

check antenna and coax connections.

i know checks sound basic but they could save you a lot of headaches later

That will need an oscilloscope to get it back right. we can fix for you. wouldn't cost much if all it is just out of alignment and nothing is broken...

TX means transmit. There are 3 settings for the meter. The top one is to measure your TX/RX that's transmit and receive. CAL is to calibrate the meter to check your SWR.

Reasons your needle may not be moving much when you key while on TX/RX. The dynamic is probably all the way down. That is your mic gain. If you turn that up when you talk the needle will swing more. If the radio is stock and not modded, you can turn this all the way up and leave it.

Also there could be something wrong with the mic. If people can hear you then its not the mic.

If people can hear you fine when you transmit, it may just be a bad meter. Not a big problem, you will just need an external meter to make sure you swr is not high.this is important because if it is over 1.5 you run the risk of blowing the final transistor.

Hi and welcome to FixYa,

Based on your description, a possible drift in the local oscillator.  Check the 10.24Mhz crystal filter and its local oscillator for output and consistency.

Good luck and thank you for asking FixYa.

What happens if you "key up" and "let off" and the transmitter "hangs", you remove the microphone plug from the Cobra ?
Will it still be transmitting or will it stop ?
If it stops, the problem is in the microphone with a "hanging" switch which you can easily clean or replace.
Iif it keeps transmitting while the mike is disconnected, there is a problem with the Rx/Tx switching circuit. This needs further investigation by use of a circuit diagram.

Had fixed the same problem yesterday. My cobra worked when it wanted to, when it didn't it looked like you explained. I found out that on my cobra the blue wire on the mike connector was broken. When it disconnects, no sound. after soldering, everything works fine.

For the money,the Cobra 29 nw/st is just as good if not better than a Galaxy. Cobra is more durable by far. I have had 3 of these cobra's in the last 30 years. Only had to replace the last one because the tractor got hit by lightning.
Sure would not pay big money for a name.