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My 2000 gtl keys up but has no audio or modulation.i tryed my mike off my 2010 & same thing. i replaced the 1969 final w/ a mossfet 510.it came up slighty,but the finals are getting very hot...any ideas?
Get rid of the mosfet finals and go back to the 1969! What modes does the modulation fail? Could very well be the AM power driver. Unless the radio is tuned improperly or a bad antenna the output stages of the Cobras are very long lasting.Get rid of the mosfet finals and go back to the 1969! What modes does the modulation fail? Could very well be the AM power driver. Unless the radio is tuned improperly or a bad antenna the output stages of the Cobras are very long lasting.
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Re: My 2000 gtl keys up but has no audio or modulation.i...
Yuo need to set the milliamps on the pre driver,and all finals,or you will quickly burn them up, anytime you replace finals, you have to readjust the milliamps...or a tune-up.....hope this helps you........
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Most likely, you have no 'voice' signal coming from the microphone. The MODulation control did not turn itself.
Check for signal from the shielded or white wire from the mike.
A capacitor could have shorted in the modulation limiter circuit, limiting the modulation to 0%.
If theres no carrier its either the finals or driver. If theres no audio its the white wire in the plug that screws into the radio..its either broke or most likely come unsoldered. It keys but no audio.
Hook up a speaker to the PA jack on the back of the radio. Put the CB into PA mode and see if any audio is coming out of PA jack. This will tell you if the AUDIO AMP IC TA7222 is good.
That's usually a defective amc stage that produces RX audio and TX modulation. It's an integrated circuit that will require a tech fixing it. You will have a transmitted carrier with no modulation, and no sound in your speaker. However, make sure you have a good mike plugged in first, and substitute a known good mike to verify it's not the mike.
you may have to scope the finals circuit on the modulation to see if all the "inline" caps are
installed correctly...
be sure your pc board is grounded in all areas as required by specs in your manual.
Make sure there is no bleedover and you are sheilding your crystals from the modulation platform.
al
Get rid of the mosfet finals and go back to the 1969! What modes does the modulation fail? Could very well be the AM power driver. Unless the radio is tuned improperly or a bad antenna the output stages of the Cobras are very long lasting.
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