TM 11-6625-298-14
volts dc, check the output directly at the
generator. If the output is still below 500 volts dc,
a. Indicator Scale Test. The indicator scale test
replace the generator.
may localize a faulty meter indication to the in-
NOTE
dicating instrument. Proceed as follows:
Low output voltage that cannot be ad-
(1) Connect LINE and GROUND terminals to
justed may be caused by an open current
known resistances.
coil in the indicating instrument.
(2) Operate hand generator crank. Note any
(c) If generator output is above 500 volts
dc, replace the controller.
the values indicated on the test set.
(3) The deviation from any marked point
three resistors R1, R2, and R3 (fig. 5-4) and Check
should not exceed 1/32 inch.
each separately with Multimeter ME-26/U. The
b. Output Voltage Test. The output voltage
resistors should check to within one percent of
test may show that the generator is defective or
their marked values. Normal values are given in
that the controller requires replacement. Proceed
as follows:
(1) Connect Multimeter ME-26/U to the
circuit, point-to-point, with Multimeter ME-26/U.
ground and guard terminals.
Check for possible short circuits in the same
(2) Turn hand generator crank until maximum
manner.
voltage is obtained Note the output voltage.
e. Intermittent Trouble. In all tests, the
(3) The output voltage of the generator should
possibility of intermittent trouble should not be
be between 500 and 550 volts dc.
overlooked. If present, this type of trouble may
often be made to appear by tapping or jarring the
volts dc; replace the controller.
equipment.
6-6. Replacement of Parts
6-7. Replacement of
Meter
a. Repair of
Ohmmeter ZM-21(*) /U
shall be
a. Remove the chassis from the case according
accomplished by competent personnel supplied
with proper tools and equipment (listed in ap
b. Unsolder the
connections to the
meter ter-
pendix C).
b. All parts are easily reached when the chassis
replaced properly.
assembly is removed from the case.
c. Remove the mounting screws and bushings
c. When removing wiring from terminals, tag
from the meter magnet, and remove the meter (fig.
each wire to be sure of correct reassembly.
5-5).
d. Take care not to damage adjacent parts when
d. Install a new meter, using the same screws
removing, installing, or connecting new parts.
and bushings that were used to mount the old
e. Replacement parts shall be identical to the
instrument. Resolder the equipment wiring to the
original parts and shall be installed in the same
meter terminals.
physical position as the original.
e. Replace the meter scale plate (fig. 6-2) with a
f. When replacing wiring, each new piece of wire
blank scale plate. Calibrate and mark the new scale
shall be the same length as the wire being
plate as shown in figure 6-4 according to directions
replaced.