On Apr 16, 8:06 am, "mikem" wrote:
I can hear the transmission in addition to the buzz. The buzz is
affected by the volume control. I don't have a squelch control for the
radio that I know of. However, pressing "test" (removing squelch)
doesn't affect the problem.

Ok, assuming the radio is "normal" (not buzzing), if you tune the
radio to a quiet channel where no-one is transmitting, with the
squelch switch in the TEST position, what do you hear?

When the radio is buzzing, tune the radio to a quiet channel where no-
one is transmitting, with the squelch switch in the TEST position,
what do you hear?

While it's buzzing, have you every tried pushing on the MX170's front
panel so as to seat it into its tray? I could be that the tray is
poorly mounted, and one-or-more pins in the tray connector are making
intermittent contact.

Does the buzzing follow engine rpm? While its buzzing, what happens if
you turn on/off heavy electrical loads, like nav/taxi/landing lights
and pitot heat?

What about turning off the right mag/left mag briefly in flight?

I'm trying to determine if the buzzing is RFI being received by the
MX170 as an on-channel radio signal (which open's the receiver's
squelch), or if it is something that is originating inside the MX170.

Ok, I'll try that. I know the unit is on its last legs. I've tried to
have it serviced but the one guy that is authorize by the FAA to open
the unit just wants to sell new units and flat our refuses to offer
any serivce/support/parts/etc (makes you want to buy his new unit,
doesn't it ).

-Robert