If the regulator still does not function correctly it
will be necessary, if local skills permit, to test
each component. All the parts should be checked
Transistors Q4 and Q5 can be checked
with an ohmmeter and the capacitors checked with
fairly accurately without removing them
a capacitance meter. The circuit board traces
from the circuit.
should be checked with an ohmmeter to ensure
that there are no cracked traces. Traces with hair-
(1) Check transistors Q4 and Q5, (see fig.
line cracks will show good at lower temperatures
and will tend to show open circuit at higher tem-
peratures. If the board seems good at room tem-
perature, but the regulator still fails, this could
Due to the connection of Q4 in the cir-
be the cause.
cuit, omit the emitter to collector check
in figure 4-2.
Table 4-1. Replacement Parts List-
Leland Airborne Model
(2) If other readings are obtained, replace
transistors Q4 and Q5.
e. Circuit Board. If no faulty components were
detected after performing tests a, b, and c, replace
the circuit board.
f. Functional Check. Check the performance of
the regulator on the test stand and make final
voltage adjustments. Voltage output should read
28 volts. If the regulator does not function prop-
erly, perform the following:
(1) Check wires and connections.
(2) Replace circuit board.
(3) Perform bench test procedures.
After final repair, check regulator on the