no malfunction in the process no 1 this is to check the switching function by the switch operating part 3 and a checking switch is set first firstly the switch s 1 is set and the lamp l 1 is set and is alternately turned on and off to indicate the checking designation of the switch s 1 when the switch s 1 is pushed the on and off operation of lamp l 1 is changed to continuous lighting and then the diagnosing operator knows that the switch s 1 is functioning when the switch s 1 is released the checking switch s 2 is set and the lamp l 4 is alternately turned on and off to indicate the checking designation of the switch s 2 in the same way the subsequent switches s 3 s 10 and the switching functions of the dials 5 6 are checked and confirmed thus the process no 2 is completed and the program advances to the sequence no 3 in the process no 2 if the operation of any switch does not change the on and off of the lamps to the on condition then something is malfuncting with the switch and the print board a is replaced if then the switch is still malfunctioning then.