Bally 5000 Plus, Manual

Page: 209 / 388

Troub l eshoot i ng ( con t ' d )
OUTPUT PORT S 2A , 4 , & 5 B I T FA I L U R E F L OWCHART
O U T P U T P O R T S
2 A , 4 , 6 5
B I T F A I L U R E
R E P L A C E B 3, B 5 , B6
ON PORT
A S S O C I AT ED W I T H
F A I L I N G B I T
S t . N o I , ,
R E P L A C E
A2 T h r u A 6
A S S O C I ATED W I T H
PORT B I T FA I L I N G
GOOD
E X T E R N A L
O U T P U T L O A D
F A I L U R E OR
F A U LTY T R A C E
NOTE 1 : These i nputs shou l d have good l og i c l eve l s 0-5 VDC .
NOTE 2: These outputs shou l d have good l og i c l eve l s 0-5 VDC .
NOTE 3 : These are open co l l ector trans i stor packs . A l og i c h i gh i nto them turns
them on and dr i ves the outputs to GND .
Port 2 I s d i v i ded i nto two 4 b i t ports , 2A & 28 . Port 2A goes through
the ULN281 3 ' s . Port 28 goes out stra i ght from the 74HC273 ' s .
A reset pu l se w i I I pu l I a l I outputs o f the 74HC273 ' s t o GND .
*
Data at i nputs must be va l i d at the fa l I i ng edge of the WPx . Look for fau lty
propagnant de l ays .
*
Good l og i c l eve l s 0-5 VDC - l ook for d i storted waveforms .
Poss i b l e f i nds
wou l d be 1-0 VDC pu l ses or 4-5 VDC pu l ses .
4 . I /O BOAR D
4-4 1