TM 55-4920-414-13&P
4-23. Test Box Circuits.
ON. Digital voltmeter will indicate between 27.5 and 28.5 V dc.
lf not, perform troubleshooting Table 4-8, see FO-3.
a. DC Power Circuit.
(4) Set TRIM switches to OFF. Digital voltmeter will
indicate O vdc. If not, replace trim switch S3.
(1) Position controls as listed in (a) through (f) below:
(5) Set DC POWER switch to OFF.
(a) AC POWER switch to OFF.
(b) DC POWER switch to OFF.
c. SAS Shut-off valve voltage test.
(1) Disconnect leads from J466R and connect to J468R pin
1(+) and pin 2(-).
(C) TRIM switch to OFF.
(d) SAS switch to OFF.
(2) Set DC POWE R switch to ON. Digital voltmeter will
indicate between 27.5 and 28.5 Vdc. If not, do continuity checks
on SAS Switch S2, FO-1, Terminal board TB1, and connector
P468R, FO-2.
(e) BOOST switch to OFF.
(f) POWER AC and DC circuit breakers to IN.
(2) Connect autotransformer to AC POWER connector,
using cable supplied with test box.
(3) Place SAS switch to ON, Digital voltmeter will indicate
O vdc. If not, replace SAS switch S2.
d. Boost DC power valve voltage test.
(3) Connect autotransformer to a 115-V ac, 60-Hz power
source and adjust for 1 15-V ac output.
(1) Place DC POWER switch to OFF
(4) Connect dc power supply positive terminal to DC POW-
E R connector pin B and negative terminal to pin A, using two
leads.
(2) Disconnect leads from J468R and connect to J469R pins
1(+) and 2(-).
(3) Place BOOST switch to OFF.
(5) Connect digital voltmeter to dc power supply, using
leads.
(4) Place DC POWER switch to ON. Digital voltmeter will
indicate between 27.5 and 28.5 vdc. If not, perform
troubleshooting Table 4-8, see FO-3.
(6) Adjust dc power supply for a 28-V dc indication on dig
ital voltmeter and then disconnect digital voltmeter from equip-
ment setup.
(5) Place BOOST switch to ON. Digital voltmeter will in-
dicate O vdc. If not, replace BOOST switch S1.
(7) Set DC POWER switch to ON. DC power green light
shall come on. If not, replace lamp. If lamp does not light, go
to Troubleshooting Chart, trouble No. 1, FO-3 and FO-1.
e. SAS Pressure Indicator Test:
(8) Push in AC POWER switch to ON position.
(1) Place DC POWER switch to OFF.
(9) Place AC POWER switch to ON. AC power red light
shall come on. If not, replace lamp. If lamp does not light go
to Troubleshooting Chart, trouble No. 2, FO-3 and FO-1.
(2) Connect jumper lead between pins 1 and 2 of cable con-
nector J467R.
(3) Place DC POWER switch to ON. SAS PRESS OFF
green light will light. If not, replace lamp. If lamp does not
light; see troubleshooting Table 4-8, see FO-1.
(10) Place AC POWER switch to OFF. AC POWER red
light goes off. If not, replace AC power switch S5.
b. Trim valve voltage circuit:
(4) Place DC POWER switch to OFF and remove jumper
lead from pin 2 and reconnect to pin 3.
(1) Set AC POWER and DC POWER switches to OFF.
(5) Place DC POWER switch to ON and SAS PRESS ON;
green light will light. If not, replace lamp. If lamp does not Iight
check cable assembly J467R and TB1.
(2) Connect digital voltmeter to connector J466R pin 1 (+)
and pin 2 (–), using two leads.
(3) Set AC POWER, DC POWER and TRIM switches to
(6) Place DC POWE R switch to OFF.
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