[R-390] Image problem solved

[Tony Casorso]

I was using an BNC to twinax adapter which grounds one side of the balanced connection. When I remove this and run the signal generator or antenna two the balanced pins without tying one side to the chassis, I can see nothing on the spectrum analyzer. That is, With thereceiver tuned to 3 Mhz and the sig gen at 1.5MHz, I see nothing at the input to the RF amplifier. 

Looking at the schematic, they show a field change which grounds one side of the balanced input but SWAPS J105 AND J106. They were not swapped in my receiver. Swapping them and then going back to my adapter gives much improved performance. I don't hear the 1650KHz broadcast station at 3.3MHz any more but I can again see some a 1.5 MHz signal at the RF amp input when the receiver is tuned to 3 MHz. But it is way down from before. The best performance for the preselector seems to be with J105 and J106 not swapped  and neither side of the balanced input grounded to the receiver chassis.