I have a early 80 model 148gtl, on AM with mic gain turned all the way down it will only dead key 3/4 of a watt but when the mic gain is turned up it squeals to a constant 2 watts no matter how high the carrier is set. PA function works but it squeals with just the mic gain cracked open. was able to touch the board between the 8719 and big crystal witch seemed to ground it down until the PA worked like it should. Any ideas?
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148 gtl squeal
- Thread starter blueridge
- Start date
The mic gain is not how you adjust the carrier. With the PA engaged, you will get squeal if the PA speaker is too close to the mic. If you're getting 3/4 of a watt with the mic gain off,then that is your true carrier reading - when the mic gain is turned up you're radio is picking up background noise and modulating it slightly.
Obviously - the squeal is a result of the mic circuit as well. Check the mic plug for a broken wire. Is there a mic gain setting that won't squeal? Is it a power mic with a weak battery? Try another mic?
i am adjusting the carrier with internal pot. no matter how much I turn it to increase carrier it will only do 3/4 of a watt (or back it off down to zero.) Guess I need to get the carrier problem fixed first then worry about it not modulating. All it will modulate is a medium pitched squeal nothing at all from the mic on AM. With PA function mic gain is way to sensitive. maybe they are related in some way and i just can't see how. thanks for your help
I would suggest starting by taking some voltage measurements at the various output stages. Whats the history of the radio?
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