TB 9-4920-454-24
(11) If % RPM indicator does not indicate between 99.9 and 100.1, perform b (4) and
(5) below.
b. Adjustments
(1) Connect frequency counter to TP6 (+) and TP3 (-) on tachometer board (fig. 6). If
frequency counter does not indicate between 97 and 103 s, adjust R71 (fig. 6) for a 100 s
indication.
(2) Connect oscilloscope CH2 input between TP1 (+) and TP3 (fig. 6). If a
symmetrical square wave is not on oscilloscope, adjust R26 (fig. 6) for best symmetrical
R71 TP6
R67 R63 R64 TP4 R59
R26 TP1
TP3
R41
R44
R45
Figure 6. Tachometer circuit board.
(3) Adjust R41 (fig. 6) for .0 on % RPM indicator (R).
(4) Adjust R44 and R45 (fig. 6) for 100 on % RPM indicator (R).
(5) Repeat a (1) through (11) above until no further adjustments are required.
11. Standard Day
a. Performance Check
(1) Set STD DAY switch to ON and TEMPERATURE switch to OPERATE.
(2) Connect equipment as shown in figure 7.
(3) Adjust audio analyzer for a 1.0 V, 70 Hz (14.286 ms) output. (Note: Set up 1.0 V
output with multimeter.)
(4) Adjust AMB TEMP (oF) control to 49. If % RPM indicator does not indicate
between 100.4 and 101.3, perform b (1) and (2) below.
(5) Adjust AMB TEMP (oF) control to -41. If % RPM indicator does not indicate
between 110.7 and 111.7, perform b (3) below.
