I am modifying one of IC-471A for weak signal work. I replaced the all caps with the ceramic ones and 3SK48 on the receiver chain is replaced with the BF981, 2SK125's are also replaced with J310s. When I was checking the circuit I find 2 capacitive diode on the gate of the first amplifier (3SK48) as far as I know this radio does not re-tune the input and it is directly getting it's voltage (which is fix) from R8V point. These two cap-diodes are 1S2090 which very well known with high noise characteristics. Is any one has a good explanation for this diode pair.
Thanks and 73