TM 55-4920-413-13&P
e. Fuel Quantity NO 1 and NO 2.
(1) Connect digital voltmeter to connector NO 1 pins G
(HI) and H (LOW), using two leads.
(2) Set FUEL QUANTITY NO 1 CAL/NOR switch to
CAL and HI/LO switch to HI.
(3) Set ON-OFF-SIM ONLY switch to SIM ONLY. Dig
ital voltmeter will indicate between 6.08 and 6.18 vdc. If not,
perform Troubleshooting Table 4-8.
(4) Set FUEL QUANTITY NO 1 HI/LO switch to LO,
Digital voltmeter will indicate between -0.1 and +0. 1 vdc. If
not, perform Troubleshooting Table 4-8.
(5) Set FUEL QUANTITY NO 1 CAL/NOR switch to
NOR and adjust variable control fully CCW. Digital voltmeter
will indicate between –0.1 and +0.1 vdc. If not, perform
Troubleshooting Table 4-8.
(6) Adjust variable control fully CW. Digital voltmeter
will indicate .63 vdc minimum. If not, perform Troubleshoot-
ing Table 4-8.
(7) Set ON-OFF-SIM ONLY switch to OFF.
(8) Disconnect leads from T1 connector NO 1 pins G (HI)
and H (LOW and connect to connector NO 2 pins G (HI) and
H (LOW).
(9) Repeat (2) through (7) above, except use FUEL
QUANTITY NO 2 controls.
Table 4-8. Troubleshooting FUEL QUANTITY NO 1 or NO 2 (AVIM).
NOTE
Before performing troubleshooting, remove DC simulator A4 board and reconnect using extender board.
Trouble
Probable Cause
Remedv.
Fuel Quantity
CR1, C3, Ul, R8, T2, R9, Cl,
First check loops 7 (+) and 8 ( -) for
No HI-CAL VOLTAGE
NO 1 – (R2) or
input 15 vac ±.5 vat. Check T2 if no
NO 2 – (R5)
voltage. Replace defective compo-
nents, Figure 4-6, 4-7, FO-2, FO-5 or
replace A4 board.
HI-CAL VOLTAGE
Trim Resistors
Remedy, use decade resistor box,
Indication out of tolerance
NO 1 – (R3)
and replace malfunctioning
NO 2 – (R6)
components, Figures 4-6,4-7, FO-2,
FO-5 or replace A4 board.
HI-CAL VOLTAGE
NO 1 – (R56) or (R9)
Output of U1 should read between
Indication out of tolerance after trim
NO 2 – (R55)
11.9 and 12.1 at TP1, Figures 4-6,
resistors checked or replaced (R3)
4-7, FO-2, FO-5 or replace A4 board.
or (R6)
LO-CAL VOLTAGE
NO 1 – (S26)
Replace malfunctioning components,
Indication out of tolerance
NO 2 – (S28)
A4 Board, Figures 4-6,4-7, FO-2,
FO-5.
LO-CAL VOLTAGE
NO 1 – (R12)
Replace malfunctioning component
Indication out of tolerance in
NO 2 – (R13)
A4 Board, Figures 4-6,4-7, FO-2,
NOR-FULLY CCW
FO-5
In NOR-FULLY
NO 1 (R1) (R12)
Replace malfunctioning components
NO 2 (R13) (R55)
A4 Board, Figures 4-6,4-7, FO-2,
FO-5
NOTE
Voltage checks are also listed on figure 4-7.
4-13
