e. Troubleshooting of an inoperative magneto timing light should begin with
a battery check. If the battery checks out OK, a multimeter should be used to make
primaries. Vibrator operation should then be checked if the battery, switch, and
transformer primaries check out OK. Glow lamps and transformer secondaries are
checked out next. The small capacitors connected across each glow lamp provide a
leakage path and cause both lamps to glow. When a capacitor is open the associated
lamp will not light. If only one lamp lights switch the bulbs to determine that
both lamps are OK. If both lamps are OK, then the capacitor across the inoperative
circuit is open. Following this troubleshooting sequence will find the problem
quickly and the malfunctioning component can be replaced. All leads and
interconnecting wires should be checked for continuity during this troubleshooting
MAGNETO TEST STAND MAINTENANCE.
a. The magneto test stand (fig. 4) is designed to functionally test
various ignition magnetos over a variable speed range of 0-4,200 RPM (revolutions
per minute). Connection to a 220/440-volt, 3-phase, 60-hertz, electrical power
source is required. All test stand components are housed within a steel cabinet
assembly. Magneto mounting adaptor and instrument and control panel components are
conveniently located and clearly nameplated for ease of operation. The removable
cover completely encloses the instrument and control panel when the instrument is
not in use. Magneto ignition capacitors, including feed-through types, can be
checked for capacitance, series resistance, ground, and leakage resistance on the
in figure 5. This schedule is intended as a guide and should be adjusted to meet
specific local conditions. Top speed (4,200 RPM) will decrease as the drivebelt
wears. When this occurs, maintenance men will have to make the variable speed
drive high speed stop adjustment listed in the technical manual. A check for top
speed can be done quickly by the supervisor during his regular inspection of the
equipment. This check, plus a visual inspection of the test stand, can help the
supervisor in determining the quality of maintenance being performed by his unit.
c. A regular schedule for calibrating the capacitor tester section of the
frequency of use will have a bearing on what time interval is appropriate. The
procedure for calibrating the capacitor tester section is in the technical manual.
Small adjustments are normally required during calibration. The need to make large
adjustments would indicate that the frequency of calibration should be increased.
DISTRIBUTOR TESTER MAINTENANCE.
a. The distributor tester (fig 6) is an electrically operated device for
testing battery ignition distributors removed from the engine. Using the tester,
maintenance personnel can determine if a distributor will meet specific tolerances
required for satisfactory operation when installed on an engine. A variable speed
device, consisting of a belt-driven cone, movable idler, and disk, is used to
control the speed and direction of rotation of the distributor under test. The
variable speed device is driven by an electric motor which operates from 115 volts,
60-Hz, single-phase, line power. Manifold vacuum is simulated by a vacuum pump
which is an integral part of the variable speed device. A stroboscope is provided
for accurately checking cam angle, spark advance, and cam lobe accuracy. Both
single and dual breaker point distributors can be tested. A tachometer measures
the revolutions per minute of the distributor shaft.
OS 010, 8-P6