electrical shock. When testing, take
Do not replace the following parts unless they are
care to prevent physical contact with
found to be defective following the cleaning and in-
bare end of the ignition cable.
e. If the filter (9) must be replaced, disconnect the
When checking spark, do not allow the
yellow lead from the terminal block and unsolder the
spark gap to exceed 1/8 inch. Greater
red lead from the terminal strip on the cover (6).
gap will cause excessively high poten-
Remove the screws (7) and lock washers (8), and remove
tial resulting in insulation breakdown
the filter from the power supply case (18).
either internally or in the ignition ca-
f. To remove the resistors (10 and 11) and diode (12),
unsolder them from the terminal strip on the cover (6).
g. If the transistors (15) must be replaced, remove the
When checking the ignition power supply, make sure
screws (13) and nuts (14) securing each transistor to the
that the input power is applied in the proper polarity.
cover (6). Unplug the transistors and remove them and
The unit will not operate when polarity is reversed.
the insulators (16) from the cover. The insulating
b. To check the operation of the ignition power sup-
washers (17) need not be replaced unless they are defec-
ply, connect it to a 28 vdc source of power. Connect the
negative to an unpainted ground and connect the posi-
tive to the yellow primary lead. Hold the end of the ig-
8-3. Cleaning and Inspection.
nition cable near an unpainted portion of the power
supply case and check for a hot spark when power is ap-
Clean all parts in a well-ventilated
plied to the primary circuit. If a hot spark does not
a r e a . Avoid inhalation of solvent
jump across an 1/8-inch gap, the power supply is defec-
fumes and prolonged exposure of skin
to cleaning solvent. Wash exposed skin
c. If the power supply fails to operate properly, dis-
thoroughly. Dry cleaning solvent (fed.
connect it from the power source, remove the four
spec. P-D-680) used to clean parts is
screws (4, fig. 8-1) and lock washers (5) and lift off the
potentially dangerous to personnel
cover (6) as far as the interconnecting wires will allow.
and property. Do not use near open
This will provide access to the interior components. Use
flame or excessive heat. Flash point of
solvent is 100°F (38°C).
(1) Check the resistance through filter FL1 (9).
a. Wipe the exterior of the ignition power supply
Refer to the ignition power supply wiring diagram,
with a cloth dampened with dry cleaning solvent (fed.
figure 8-2. Resistance from test point A to test point B
spec. P-D-680). Take care to prevent solvent from enter-
must be 0 ohms. With the meter + probe at point A and
ing the interior of the unit.
- probe at point C, resistance must be infinite. With +
probe at C and - probe at A, resistance must be 700 to
The output of the ignition power sup-
800 ohms. Replace the filter if it is open or grounded.
ply is high enough to cause severe