Technics SX-KN1400 - Precautions before Servicing the Main Circuit

PRECAUTIONS BEFORE SERVICING THE MAIN CIRCUIT
Note: In the initial production (over several months) of this model (Type A), FLASH ROMs (EEPROM) were used for the PROGRAM
ROMs. In models produced thereafter (Type B), FLASH ROMs were not used. If changing any of these ICs, service the MAIN
CIRCUIT as explained here following.
@ About the FLASH ROM
The FLASH ROM can be electrically erased and rewritten. This model is designed so that the repair technician can easily write
and change programs and data in the FLASH ROM, by using a floppy disk.
Block Diagram of MAIN CIRCUIT CPU and peripheral ICs
y y i i
PROGRAM || PROGRAM DATAROM || DATAROM os
ROM (ODD) || ROM (EVEN) (ODD) (EVEN)
8M bit 8M bit 16M bit 16M bit
FLASH ROM || FLASH ROM MASK ROM || MASK ROM
(IC2)
(IC4) (IC5) (IC7)
* FLASH ROM contents
1C2: MAIN CPU program (ODD)
IC4: MAIN GPU program (EVEN)
TYPEB . as
MAIN CPU
(IC6)
i i i i
Socket Socket MASK ROM MASK ROM mee
(ODD) (EVEN)
16M bit 16M bit
(IC2) (IC4) (IC5) (IC7)
i How to distinguish Type A from Type B
While pressing PANEL MEMORY buttons 1, 2 and 3 at the same time, turn the power on. The model type can be determined from
the resulting display.
For Type A, “DEVICE=FLASH ROM” is shown on the display.
For Type B, “DEVICE=MASK ROM’ is shown on the display.