TB 9-6625-1866-50
18. 500-Volt Range and Stability
a. Performance Check
(1) Position UUT A, B, C, D, and E dials to 4.9, 9, 9 and 10 and RANGE switch to
500.
(2) Turn OPERATE-CALIBRATE switch to CALIBRATE and hold.
Adjust
CALIBRATE control for null on meter. Release OPERATE-CALIBRATE switch. The
CALIBRATE control will be within 90 degrees of midrange. If not, perform b below.
(3) Adjust dc voltage standard (A2, table 6) to 500 volts.
(4) Turn NULL switch to 10, 1, and .1 while adjusting dc voltage standard for 0
(zero) indication on UUT meter. Dc voltage standard will indicate between 499.75 and
500.25 volts. If not, and no adjustment was made in (2) above, perform b below.
(5) While maintaining null on UUT with dc voltage standard, vary autotransformer
(A1, table 6) from 105 to 125 volts (wait 1 minute at 105 and 125 volts). Dc voltage
standard output will remain between 499.75 and 500.25 volts. If not, and no adjustment
was performed in (2) or (4) above, perform b below.
(6) Adjust autotransformer output to 115 volts.
(7) Turn UUT NULL switch to VTVM.
(8) Adjust dc voltage standard for 0 (zero) indication on UUT meter.
b. Adjustments
(1) Turn NULL switch to VTVM and CALIBRATE control to midrange. Adjust dc
voltage standard for 500.000 volts.
(2) Turn NULL switch to 10, 1, and .1 while adjusting R121 (fig. 2) (rear of
AN/USM-98B). Continue adjustment until NULL is obtained in .1 NULL switch position.
(3) Turn OPERATE-CALIBRATE switch to CALIBRATE and hold. Adjust R318
(4) Release OPERATE-CALIBRATE switch.
19. 50-Volt Range
a. Performance Check
(1) Turn VOLTS RANGE switch to 50.
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