[R-390] Distortion in MGC on strong signal

[Barry]

When tuned to strong stations in MGC mode, my R390A is driven into
distortion.  Monitoring the Diode Load, I'm seeing approximately -60V when
tuned to a strong station.  Backing the RF Gain control to where the Diode
Load reads more around -30V causes the signal to sound normal again.
Switching to AGC (any AGC speed) causes the Diode Load to drop to about -30V
and the signal sounds normal as well.

I can reduce the IF Gain to almost zero and cause the Diode Load in MGC mode
to be around -30V with the RF Gain at "10", but I'm sure this is too low of
a setting for the IF Gain Control.  I've followed the manual's procedure
(150mV into the IF deck and set for -7V Diode Load) as well as backing it
off slightly for Chuck Rippel's procedure so setting it far enough back to
keep the Diode Load down to an acceptable level when the RF Gain is at "10"
is not the correct solution.

I assume the radio should not be acting this way, right?  If not, any
suggestions on where to look for problems?

Thanks,

Barry - N4BUQ