COMP COAXIALSTRUCTURE F72731
FUEL QUANTITY INDICATOR
TO COMPENSATOR AND TANK UNITS
DO NOT CONNECT
SIMMONDS PSD40-1 SYSTEM TESTER WITH THE F72731 CABLE
Test Equipment Set-Up for Resistance Measurement
Figure 504 (Sheet 3)

EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù.
 AIRPLANES WITH ANALOG FUEL QUANTITY ú 28-41-00
 INDICATORS  ú  CONFIG  2
 ú  01A  Page 522
 (SIMMONDS SYSTEM TESTER)  ú  Jul 15/93 

BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
C40121
A
737-300/400/500MAINTENANCE MANUAL
 (k)  
If you have a PSD40-1 system test unit, set the FUNCTION SEL switch to EXT CAP.

 (l)  
Set the FUNCTION MEASURE switch (PSD40-1) or SELECT switch (PSD60-1) to TU.

 S 415-064-002
 (2)  
Do this procedure: "Fuel Summation Unit Installation" (AMM 28-41-81/401).

 S 825-043-002

 (3)  
Set the capacitance trimmer.

 NOTE: This step sets the airplane wiring to a standard
____ capacitance value of 16 pf. This will make it easier to find problems with the capacitances of the equipment in the fuel tank.
 (a)  
Get access to the bussing plug installed on the spar for the applicable tank (Fig. 501).

 (b)  
Disconnect the electrical connector from the bussing plug.

 NOTE: Do not disconnect the bussing plug from the receptacle
____
 installed on the spar.

 (c)  
Get access to the capacitance trimmers on the right side of the control stand, above the hand microphone receptacle.

 (d)  
Turn the applicable capacitance trimmer with a screwdriver until the test unit shows 16.0 pf.

 (e)  
If it is not possible to set the trimmer so that the test unit shows 16 pf, examine the airplane wiring between the bussing plug and the indicator.

 (f)  
Connect the electrical connector to the bussing plug installed on the spar.

 S 975-044-002
 (4)  Measure the empty tank capacitances.
 (a)  Measure the capacitance of the tank units.
 EFFECTIVITYùùùùùùùùùùùùùùùùùùùùùùùùùùùùùù.
 AIRPLANES WITH ANALOG FUEL QUANTITY ú  28-41-00
 INDICATORS ú CONFIG 2 ú 02A Page 523 (SIMMONDS SYSTEM TESTER) ú Jul 12/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 (b)  The capacitance must have these values with the applicable tolerance: TANK CAPACITANCE (pf) TOLERANCE (pf)
 No. 1 and 2 506.6 |7.8 Center 180.2 |2.7
 1)  If the capacitance is out of the correct range of values, do this task "Tank and Compensator Units Test" (AMM 28-41-21/501) to find a bad tank unit or wire harness.
 (c)  
Set the FUNCTION MEASURE switch (PSD40-1) or the SELECT switch (PSD60-1) to COMP.

 (d)  
Measure the capacitance of the compensator. 1) The capacitance must be 40.2 pf with a tolerance of |1.2 pf.

 2)  If the capacitance is out of the correct range, do this task: "Tank Unit and Compensator Test" (AMM 28-41-21/501) to find the problem with the compensator or the wiring.
 S 825-063-002
 (5)  Adjust the capacitance trimmer.
 (a)  
Get access to the capacitance trimmers on the pilot's instrument panel, P1, above the hand microphone receptacle.

 (b)  
Turn the applicable capacitance trimmer until the system test unit shows the applicable capacitance value from this table: 1) Turn the trimmer with a screwdriver. 2) Remove the screwdriver. 3) Let the value on the test unit become stable. 4) Continue this procedure until the test unit shows the

 correct capacitance. 5) These are the applicable capacitance values:
 TANK  CAPACITANCE (pf) No. 1 and 2 506.6 Center 180.2
 S 825-045-002
 (6)  Adjust the test unit to give the capacitances equivalent to a full fuel tank (Fig. 503).
 (a)  
Set the FUNCTION SEL switch on the test unit to INT CAP (PSD40-1) or set the FUNCT switch to MEASURE INT (PSD60-1).
　
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