S 815-123
(24)
If the problem continues do the check at the FQPU, M7860.
J.
Densitometer Test (at the FQPU)
S 655-125
(1)
Make sure the fuel level is fully above the densitometers (transfer fuel if it is necessary) (AMM 28-26-00/201).
S 865-119
(2)
Open these circuit breakers and attach DO-NOT-CLOSE tags:
(a)
On the main power distribution panel, P6:
1) 6D5, FUEL QTY 1
2) 6D6, FUEL QTY 2
(b)
On the DC power distribution panel, P180:
1) 180M9, FUELING PWR - HOT BAT
2) 180C25, FUELING LTS PANEL
3) 180C26, FUELING LTS RECP
(c)
On the left power distribution center, P414:
1) 414F22, FUELING PWR
S 015-120
(3) Open the electronics access door (125B) to get to the fuel quantity processor unit (FQPU), M7860.
NOTE: The FQPU M7860, is immediately forward of the access
____
door.
S 035-121
(4)
At the FQPU, M7860, loosen the eight captive screws on the access panel assembly.
(a)
Move the panel down.
S 215-130
(5) Make sure the LED indicator light on the applicable IFQC card is not on.
S 415-131
CAUTION: YOU MUST CAREFULLY DO THE STEPS IN THE TASK BELOW TO REMOVE THE
_______ IFQC CARD. A FAILURE TO TO DO THE STEPS CORRECTLY CAN CAUSE DAMAGE TO THE EQUIPMENT.
(6) Do this task to remove the applicable IFQC card from the FQPU card file: ESDS Circuit Card Removal (AMM 20-41-02/201).
EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù. ú
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BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
747-400 MAINTENANCE MANUAL
S 485-124
(7)
Do these steps to install the PSD747-21 circuit card adapter. (Fig. 505).
(a)
Install the PSD747-21 circuit card adapter into the slot of the removed IFQC card.
(b)
Make sure the PROCESSOR arrow on the circuit card adapter points up when you install the adapter in the FQPU.
(c)
Push the card extractors to engage the adapter with the mating connectors.
S 485-135
(8)
Make sure that the DENSITOMETER switch is set to the OFF position.
S 485-278
(9)
Connect the test equipment.
(a)
Use the PSD747-20 interconnect cables and connect the PSD747-21 circuit card adapter with the PSD747-2 SIGNAL connectors.
(b)
Attach the PSD60-1 or PSD60-2 cables to these connectors (Fig. 505):
NOTE: Make sure you attach the PSD747-2 test set and the
____ PSD60-1 or PSD60-2 to the same aircraft ground. You could cause stray capacitance values if you do not ground the cables correctly.
1) LOZ and the HIZ connectors on the PSD747-2 test set 2) LOZ and HIZ connectors on the PSD60-1 or PSD60-2 field calibration unit.
S 815-137
(10)
Set the DENSITOMETER switch to the DENSITY position.
S 815-279
(11)
Make sure the BAT indicator is not on.
(12)
After a short time, look at the DENSITY GOOD/BAD indicators.
S 815-138
NOTE: The BAD indicator light for the R1-R8 resistors will come on
____ when the DENSITOMETER switch is in the DENSITY position. This does not show that the R1-R8 resistors are BAD.
S 815-139
(13)
If the GOOD indicator is on, continue with the test.
S 815-280
(14)
If the BAD indicator is on, stop the test.
(a)
Put the DENSITY switch to the OFF position.
(b)
Remove the test equipment.
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