Galaxy 44v squealing

[smokinjoe]

I have a Galaxy 44v main board #360014b that when you key the radio up it wants to squeal even with the talk back turned off. I noticed that if i remove the top cover on the radio it stops squealing and soon as i replace cover it starts squealing again. Could something be leaking RF's inside the radio causing this. I also noticed that if i turn the RF power up to about a 4 watt carrier it will stop squealing Not sure where to start. Also forgot to mention that it doesnt matter how i adjust the mic gain it still squeals. Thanks

[Rick]

Jack,
Check the choke on the Mic jack board also check the insulator plates on the Driver and Final they must be ceramic insulator types.

[smokinjoe]

Thanks for the reply Rick i have checked the chokes and the insulators are the ceramic type. Also i noticed that when i have the radio keyed i can turn the volume knob and the squeal will go from like a faint mic squeal with the volume turned up to a bad feed back squeal with the volume turned all the way down. As i said in the first post it also goes away when i change the carrier from 1 watt to 4 watts i have also tried different mics with no luck . Thank you for your time.

[Rick]

It sounds like the audio chip (IC8) is not going in mute in the TX mode. Check pin 5 in TX it should be about 5 to 6 volts, you can check if this is the fault by soldering a 10K resistor from pin 5 to the collector of TR38, if the problem go away then check TR39 and D80. I have come across D80 o/c quit a few times.

[smokinjoe]

Thanks for your help Rick when i checked the insulators on the final the first time i just glanced at them to confirm they were the ceramic type but upon closer inspection of them found that it was cracked and seperated a little so i replaced it and every thing is fine now. Thanks again