Tuning steps change for all mode Icom IC-275/475/575/1275
The IC-275/475 FM-Step selectmatrix use these diodes on the front unit:
(type 1SS53) D41, D42, D43, D44, (D45), D46
Note: diode D45 is not present but solder holes exist for it on the board
just between D44 e D46
installed diodes are marked with X :
D41 D42 D43 D44 D45 D46 D48 Steps DB4 DB5 DB6 DB7
. . . . . . . 10.0 Hz
. . . X . . . 100.0 Hz 1 0 0 0
. X . . . . . 1.0 KHz 0 0 1 0
X . X . 5.0 KHz 1 0 1 0
. . . . X . . 10.0 KHz 0 1 0 0
. . . (*) X X . 12.5 KHz (*) 1 1 0
. . . . . . X 25.0 KHz 0 0 0 1
X . X . . . . 1.0 MHz 0 1 0 1
To set a step of 12.5 KHz in FM mode (TS button off) it is not
necessary disconnect the diode D44, just insert the diode D45
(IN4148 or similar) near D44 and "voil? les jeux sont faits".
Unscrew the two lateral screws and unlock the front panel.
Remove also all the connectors of the front board and after that
unscrew ALL the screws of the metallic shield covering the front board.
It seems too much complicated insert the diodes from the component
side of the front board, so it is better insert D45 from the solder side.