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APRIL 1981
Williams
C8363 MASTER DISPIAY BOARD
TROUBl£SHOOTING PROCEDURES
INTRODUCTION
This section provides test procedures for the C8363 Master Display Board (7-digit). The
procedures assume that the fault has been isolated to the Master Display or CPU Boards
by substitution or disconnection of slave displays. Separate procedures are provided for
the strobe circuits, the segment drivers, and the blanking circuit. Refer to the figure on page 7.
SEGMENT DRIVER
Set the AUTO-UP/MANUAL-DOWN switch to MANUAL-DOWN and depress
ADVANCE to enter the Display Digits Test (depress twice with green-labeled flipper
ROMs and depress once with blue labeled flipper ROMs). Depress ADVANCE to step
through all digits and compare the inputs to IC3 (Al-Dl) and IC4 (A2-D2) and individual
outputs of IC3 and IC4 (segments a-g) against the required signals as shown in the figure
and the chart below.
With blue-labeled flipper ROMs, comma segments are produced. The Al-Dl and A2-D2
BCD signals produce segments for decimal numbers with the following levels:
BCD
O
1
2
3
4
5
6
7
8
9
Al (A2)
Bl (B2)
Cl (C2)
D 1 (D2)
Low
Low
Low
Low
High
Low
Low
Low
Low
High
Low
Low
High
High
Low
Low
Low
Low
High
Low
High
Low
High
Low
Low
High
High
Low
High
High
High
Low
Low
Low
Low
High
High
Low
Low
High
With a display of all 8' s, all segments should be on. With a display of all I's, only segments
b and c should be on and segments a, d, e, f, and g can be checked for the off condition.
Displaying all 2' s allows a check of segment c for the off condition and displaying all 5' s
allows a check of segment b.
ADVANCE in manual to a display of all 8' s and if any segment is out, check corresponding
ICl and IC2 output for the correct voltages for the on condition (as shown in the figure).
Next, ADVANCE in MANUAL to the all I's display and check segments a, d, e, f, and g (if
any are on) for the off condition; then ADVANCE to all 2' s and check segment c (if on) for
the off condition; finally, ADVANCE to all S's and check segment b (if on) for the off
condition.
STROBE DRIVERS
Use the Display Digits Test. Check the input, driver input, and strobe driver output for the
waveform and/or voltages shown in the figure. Note that the de voltages indicated in this
diagram represent average values with the circuit activated 1/16 of the time and will vary
depending on the test equipment used and the present load determined by the number of
segments illuminated for the current digit displayed.
BlANKING CIRCUIT
The blanking circuit checks the BLANKING timer output from the CPU Board. If
BLANKING goes low, the input (inverted by ICl 1) will inhibit the segment decoders IC3
and IC4. To check for proper blanking levels, depress the DIAGNOSTIC pushbutton on
the CPU Board with the coin door closed.
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