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Icom IC-751 (IC 751 IC751) Switch Matrix
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This following chart was generated by shorting out the matrix points and
watching the function that is performed. Some are intuitive already from the
schematic. There are only a couple of "extra" functions in the matrix (ie, USB
and LSB, Reset 100&10 Hz [The TS switch does this as well]). The KEY? GENE
switches (Y0) are accessed by the RC-10 controller, but I noticed that some
"removed" circuitry in the rig was designed to switch the digit switches
on the RC-10 controller to the KEY? HAM array (Y3), effectively making the
switches directly access each band. However, the removed circuitry (a set of
switching transistors) is replaced by a solid jumper to Y0 :-(. The "empty"
slots in the following table showed no perceivable function.
The Y5 matrix, acted like it was shorting some other behavior out causing
the rig to switch to the specific memory channels (you can observe a
binary + 1 selecting behavior) temporarily.
IC-751A Switch Matrix (W/ Function)
DB0 DB1 DB2 DB3 DB4 DB5 DB6 DB7
+-------+-------+-------+-------+-------+-------+-------+-------+
| KEY0 | KEY1 | KEY2 | KEY3 | | | | |
Y0 | GENE | GENE | GENE | GENE | SCAN | | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
| MHZ/ | MHZ/ | | | VFO | VFO/ | HAM/ |Disable|
Y1 | BAND | BAND | | | A/B |Memory | GENE |RIT/XIT|
|__Up___|_Down__|_______|_______|_______|_______|_______|_______|
| | | | Clear | A=B | | | |
Y2 | FUNC | | |RIT/XIT| (B=A) | |MWrite |M->VFO |
|_______|_______|_______|(->VFO)|_______|_______|_______|_______|
| KEY0 | KEY1 | KEY2 | KEY3 | | | | |
Y3 | HAM | HAM | HAM | HAM | | | | |
|__BAND_|__BAND_|__BAND_|__BAND_|_______|_______|_______|_______|
| | | AM | CW | RTTY | SSB | | |
Y4 | LSB | USB | (FM) | (NAR) | (NAR) | (REV) | FM | LSB |
|_______|_______|_______|_______|_______|_______|_______|_______|
| M2 | M3 | M5 | M9 | M17 | M33 | M65 | M29 | Danger
Y5 | Prio. | Prio. | Prio. | Prio. | Prio. | Prio. | Prio. | Prio. | Will
|or_M1__|_______|_______|_______|_______|_______|_______|_______| Robinson
| MODE | Reset | Change| | | |Disable| Scan |
Y6 | Scan |100&10 |Memory | | | |RIT/XIT| OFF |
|_______|__HZ___|On_Dial|_______|_______|_______|offset_|_______|
| I/O | I/O | HOLD |Altern-|Band W/| | | |
Y7 |Option | Option| Scan |ate VFO|DB6&DB7| | | |
|___RP__|___WP__|10_Sec.|_______|or_TS__|_______|_______|_______|
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