Question about Cobra 29 LTD CB Radio

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Not transmitting or receving (transistors burnt out)

How do i figure out the codeing on the transistors to replace them with the proper ones

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  • Wes McKay
    Wes McKay May 11, 2010

    do you mean the model transistor or what the legs are?


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If its not transmitting or receiveing its probably a problem in the power supply or antenna/coax.The big transistors you see inside are the output transistors for the transmitter section and would not effect the receive. Does it pick up static with the squelch is open? if so the audio section probably works ok.Have you tried a watt meter with a dummy load to see if the transmitter is working?Before you change components you have to narrow down what section is not working and know why its not working otherwise the new transistors could just blow too if its transistors that are bad.more information is really needed to diagnos the problem.

Posted on Jan 15, 2009

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One radio transmits the other does not

Connect a small 12volt lamp across the antenna output socket.
if the lamp glows when the transmit button is pushed the problem is in the aerial.
If the lamp does not glow the output transistor in the cb radio is blown and requires replacement by qualified person ..

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1 Answer


Can you see the s-mete if it has one moving up and down on any channel? Do you hear any audio at all? could be a couple of things. Bad mic switch or mic cable, bad antenna or coax, bad audio amp. To check the audio amp plug in a speaker to the PA jack, put the PA switch on PA then press the mic to talk. If it works the audio is fine the mic is good and the mic cable is good. Noiw plug the speaker into the speaker jack, do you hear anything? If not then your antenna or coax has a problem, fix or replace antenna or coax.

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It could be small transistors--in the back where the light and transmit hook up. One small transistor will shut down transmit & possibly receive. Get it serviced at a radio repair shop. if you know how do it yourself. Change all small transistors to 2sc3904 or 2sc 3906 at "Radio Shack."

Apr 30, 2011 | Cobra 29 LTD CB Radio

1 Answer

I have a realistic TRC-418C.B. Model#21-1511A I can recieve but not transmit. What should I be looking for??? I let some one barrow it and they FLEW home. could the airport scanner done some thing?? Also...

Sounds like it burnt a final out. Its a 3 prong transistor near antenna out. Its mounted on a heatsink. Look for 2sc2078. Radio Shack will sell these or order them. If you want to solder in a new one. Disassembling the antenna can cause SWR which will burn up your transmitter. Make sure antenna is put together properly.

Apr 15, 2011 | Radio Communications

1 Answer

The wire broke off my aerial and the transmit button was pressed with no proper aerial, mended the aerial, now I get an SWR reading on my meter of 1.2 but no power output reading and no reply's to calls !!...

it sounds like u fried your final.. Its only your driver/buffer transistor that's working right now..
if u can identify them usually large square transistors close to the aerial conn,
look for # on front of transistor buy replacement and replace . if your handy with the iron it should be a cake walk.

Dec 22, 2010 | Midland 77-099 CB Radio

1 Answer

I can't hear people

Make sure you don't try to transmit without a proper CB antenna, it will damage & blow out the power transistors! If you have another CB close by, try listening without the antenna attached If you even faintly hear whats transmitted by the other CB, your antenna cable is probably shorted out... AGAIN don't try to transmit with no antenna or a shorted cable it will damage the unit!

Oct 22, 2010 | Cobra 29 LTD CB Radio

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Im installing a west marine vhf500sc on my tugboat. I have all the power, ground, and antenna hooked up properly but yet it still wont produce power. What should i do...

try replacing the microphone, some radios will not even show power with a faulty microphone. also, check that you have power to the hot wire and the ground is grounded by use of a multi-meter.

Jan 07, 2010 | Radio Communications

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