Oki 3321, 3320 specifications Figure C-3-3

A

Yes Are ALE, PSEN, RD, WR, signals as specified in Figure C-3-3?

542ns

180ns

ALE

			PSEN		271ns				542ns
		RD/WR
						Figure C-3-3
No		Replace the Q3.
Yes	Are (T1) SELECT and (INTO)						BUSY	signals low level?
No		Check Q501 on the SDDV board.
Yes	Are +9V and -9V input to Q1?
No		Replace defective component in +9/–9 volt control circuit.
Yes	Is pin 1 SSD signal of Q3 High level?
No		Replace the Q3.
Yes	Is pin 11 SSD of Q1 low level?
No		Replace the Q1 or the CN1?
Yes	Is the RxD of Q3 as specified in Figure C-3-4?
RxD
				ST bit						SP bit

SSD

Figure C-3-4

No Replace the Q2.

Yes Replace the Q3.

5V

0V

5V

0V

5V

0V

5V

0V

5V

0V

C – 9