Basic HTML Version
The 4 "quarter hour" optos are broken by the minute hand as it passes the quarter hour marks.
The "hour" optos change as the minute hand is near the 30 minute opto. The 4 "hour" optos
are examined when the minute hand passes through the "00 minutes" opto.
The following table shows how the hour optos are decoded into the "derived" hour. If this is a
different value than the clock shows (with the minute hand near "00") then use the table to find
the faulty opto:
Hour
Hour
Hour
Hour
Derived
4
3
2
1
Hour
X
X
12
X
1
2
X
3
X
X
4
X
X
X
5
X
X
6
X
X
X
7
X
X
8
X
9
X
X
10
X
X
X
11
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Twilight Zone 1-19