[TenTec] Omni-D with an Annoying 1khz Tone

[forum4ll at verizon.net]

Well, I finally used an external power supply to power Omni-D frequency counter and see if the whining tone would go away. On the first three bands, no whining could be heard, hooray. However, at 10mhz and above, the whining is more of a faint tone which is  -12db down from the problem which I think I can live with. So with that, is it safe to assume the source of this whine is coming from some other board that is sharing the 13.8V supply?

I made a list of all the boards sharing that supply but I'll probably look at the audio side tone board first since that is closest to the speakers and work my way backwards with an oscilloscope checking all the bypass caps to ground.

Lyman KK6LPW