Re: Cobra 29 NW ST No Sound, litesup, keys up, needle...
It sounds like it may have been hooked up backwards when hooked up to the battery charger. If so it probably blew the polarity diode (D23) (1N4004) and with no sound it probably blew the audio IC (TA7222AP) mounted to the case of the radio. Also look at all of the large capacitors and make sure that the tops are not swollen or busted open if so they need replaced also.
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If you have reversed power leads you may have blow the protection diode and fuse. Well I am sure the fuse is blown if this is the case you may have been lucky and only popped the fuse if you replace the fuse an it blows also you will know for sure but be sure you don't use a larger fuse. Now we will assume the worst that the diode is blow. Remove the speaker side cover and with a pair of side cutting wire cutters cut D23. If you have trouble finding it its the second component from speaker jack next to a cylinder electrolytic capacitor it is a black component. This will stop your fuse blowing problem that was created when reversing polarity but unless you replace the diode you have disabled your protection if it happens again. It is a good practice to turn on/off switch to off position before connecting power. Take care .....hope this was of help.
first of all you are going about it wrong. To set your SWR you check it on channels 1 , 19 , and 40. If you reading is higher on 1 than on 40 you have to shorten your antenna . if its higher on 40 than on 1 then you have to lengthen it. before you do any adjustments to it ,loosen the set screws and let the antenna fall to the bottom then bring it up 1/4 " and tighten the screws. You should also use an external SWR meter not the one on the radio. Thats good for making checks every once and a while. With the meter you key the mic and have the needle go to set then put it on for and key the mic to obtain you reading . Anything under a two is good .
The symptom sounds like a bad Microphone connection or a bad microphone!! The Cobra has a built in circuit that wont allow you to hear anyone until the microphone is plugged in and the no transmit part will also do the same. Try another microphone that is wired right for that radio before you do anything else!! let me know!!
Sounds like you may have a leaky or shorted capacitor somewhere in the power circuits, or a defective transistor in the same circuits since it affects both the transmitter and receiver. Common problems with receive and transmit intermittance can also be the antenna or its connections. The fact that it goes away if the radio is turned off, then on again after a short time points to something common in the power supply section. Unless you have test equipment and a working knowledge of electronics it will be difficult for you to troubleshoot on your own.