Table 4-1. Replacement Parts List Leland Airborne Model

TB 9-2920-225-34-1

d. Transistors.

If the regulator still does not function correctly it

will be necessary, if local skills permit, to test

NOTE

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

4-3), inaccordance with figures 4-l and 4-2.

and will tend to show open circuit at higher tem-

peratures. If the board seems good at room tem-

NOTE

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

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.

NOTE

After final repair, check regulator on the

test stand.

4-4