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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1 Answer

R58 and driver smoked.


Could be that the PA is also shot. ALSO, check your antenna switching diodes, they quite often open and/or short which can cause lots of problems. Check your current drain in transmit. It should be 2 to 3 amps in transmit, and about 1/2 an amp in receive.
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1 Answer

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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 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,
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1 Answer

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