[ICOM] 765 receive problem

[Glen Rosenthal]

There's a problem with the receiver in my 765 that is somewhat perplexing 
and it is more noticeable on CW, especially when the CW narrow filter is 
selected and moreso when the 250Hz filter is selected during the first 20 
minutes or so of warm-up. It is barely noticeable when in one of the 
sideband modes.

For lack of a better description, it sounds as though the IF shift is 
changing by itself in a warbling fashion. When this is occurring, I can turn 
the IF Shift knob to duplicate the sound and the effect it has on the 
desired signal in the passband. It does not mitigate the problem. It happens 
whether or not the PBT mod is engaged or disengaged by way of the IF Shift 
button. When this is occurring, the unit will not receive briefly, then it 
pops back to normal. After about 20 minutes or so of warm up, the receiver 
performs perfectly. When the unit is first turned on after it's been powered 
down for the night, it does not happen - only during the warm up period.

The receiver is perfectly aligned to specifications, the trimmer caps have 
been replaced, and the PBT mod has been done, but none of these has 
prevented the unit from doing this.

I hope I've described this accurately enough to get some direction as to 
where to look.

Thanks for any suggestions.

Glen