President Washington noise on transmit

[Lkaskel]

Hey Gang,
I have a President Washington (858 board) that I was told has a little A/C hum on transmit. I tried a few mics and the was told the hum is still there. I put it on the bench and hooked it up to the scope. When I key on LSB the RF is almost non-existent. When I add the smallest amount of modulation the radio will then emit a small RF signal. I can see it on the scope but it is not enough to show on a modulation/watt meter. If it touch the metal case the RF signal drops to nothing. The mic is plastic.

Any thoughts?

 

[walterjn]

Touching the metal case causes the rf to vanish, maybe a ground issue? Just spitballing there... pretty sure that those with more experience will be here shortly to give you a better answer that proves my answer is wrong.

 

[nomadradio]

Need another mike.

Any 4-pin mike wired for a Cobra or Galaxy radio will work.

73

 

[Chevboy0167]

Check the onboard power supply for proper voltage and amperage. Then hook up an external supply or 12v battery and compare results.