Power Distribution Circuits and Components

TM 11-5820-509-35

(3) Power Distribution Circuits and Components

Item

Indication

Probable trouble

Procedure

XMTR OUTPUT meter M101

+26.5-volt dc lamp circuit

Check continuity from K1-7 to

does not read in the banded

defective.

POWER-LIGHTS switch S1-6:

portion of its scale when

to antilock relay K6- 1, to in-

BATTERY TEST switch is

ductor L3, and resistor R23.

pressed.

Repair circuit as required.

Resistor R23 defective.

Check resistance of R23

(normal 681K ohms). Replace if

defective.

BATTERY TEST switch S2

Check continuity from R23 to

(fig. 3-87) defective.

S3A (NO) to S3A (COM) with

switch pressed: replace S3 if

defective.

PA filter box FL2 (fig. 3-5)

Check continuity from S3A

defective.

(COM) to FL2-11. Repair circuit

if open. Check resistance be-

tween FL2-11 and FL2-24

(normal 29.0 ohms). Repair FL2

if abnormal reading.

Caution:

Before continuing this procedure, disconnect the lead from the positive ( + ) terminal of XMTR OUTPUT meter M101. Do not

attempt to measure the meter movement resistance.

e. PA filter box circuit shorted to

e. Check for short to ground at

ground.

FL2-11 and FL2-24. Repair

circuit C216, C203, L203, as

required.

Meter bypass circuit defective.

Check continuity from FL2-24

to lead removed from + meter

terminal. Repair if open. Check

C107 for short; replace if

necessary.

Note:

Reconnect the positive ( + ) meter lead removed above before proceeding to the next procedural step.

g. XMTR OUTPUT meter

g. Remove and replace M101.

defective.

Panel lamps in main compartment

a. Panel lamps DS1 and DS2

a. Replace burned out lamp bulbs.

(DS1 and DS2) (fig. 3-87) fail to

burned out.

light when POWER-LIGHTS

b. Lamp circuit defective.

b. Check continuity from S1-10 to

switch is rotated to LIGHTS

each lampholder; check con-

Hl.

tinuity from each lampholder to

ground. Repair any defective

circuits.

c. POWER-LIGHTS switch (lamp

c. Replace switch S1.

circuit) defective.

Panel lamps in power amplifier

a. Panel lamps DS101 and DS102

a. Replace burned out lamp bulbs.

compartment (DS101 and

are burned out.

DS102) (fig. 3-87) fail to light

b. Lamp circuit defective.

b. Check continuity from S1-10 to

wheat DS1 and DS2 are lighted.

FL2-9; repair circuit if defective.

c. PA filter FL2 (gig.. 3-5) defec-

c. Check resistance from FL2-9 to

five.

FL2-22 (normal 29 ohms}.

Repair circuit C218, C229, C206,

and L205 as required.

d. Lampholder or circuit to FL2

d. Check continuity from FL2-22

defective.

to each lampholder, and from

each lampholder to ground.

Repair any defective circuits or

replace lampholder.

Panel lamps remain bright or go

Dimming resistor R6 is defective.

Check resistance of R6 (normal

out when POWER-LIGHTS

180 ohms; replace if necessary.

switch is rotated to LIGHTS

Check continuity from S1-9 to

LO.

S1-6; replace S1 if defective.

3-77