BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
(h)
Disconnect the UNSHIELDED wire bundle of the test harness from the INSULATION LO-Z receptacle on the test unit.
(i)
Connect the COMP probe to the INSULATION LO-Z receptacle.
(j)
Set the INS TEST POINTS switch to LO-Z/HI-Z.
(k)
Read the resistance of the compensator.
(l)
Make sure the resistance on the test unit display is more than 250 megohms.
(m)
Set the TEST FUNCTION switch to CAP BRIDGE.
(n)
Turn the D.F.CONTROL knob counterclockwise to the 12 o'clock position.
NOTE: Some Barfield testers have a stop at this position,
____ but some testers do not have this stop.
(o)
Disconnect the COAXIAL wire bundle of the test harness from the INSULATION HI-Z receptacle on the test unit.
(p)
Connect the COAXIAL wire bundle to the HI-Z COAX receptacle.
(q)
Disconnect the COMP wire bundle from the INSULATION LO-Z receptacle.
(r)
Install a shorting cap on the COMP wire bundle.
(s)
Remove the shorting plug from the UNSHIELDED wire bundle.
(t)
Connect the UNSHIELDED wire bundle to the LO-Z TANK receptacle.
(u)
Install a shorting cap on the COMP receptacle on the test unit.
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(2)
Do this procedure: "Fuel Summation Unit Installation" (AMM 28-41-81/401).
S 825-060-003
(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 on the spar.
(c)
Get access to the capacitance trimmers on the pilot's instrument panel, P1, above the hand microphone receptacle.
(d)
Set the TANK CAP PF thumbwheels on the test unit to 16.0.
(e)
Turn the applicable capacitance trimmer with a screwdriver until the test unit shows a minimum capacitance value.
(f)
Connect the electrical connector again to the bussing plug installed on the spar.
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AIRPLANES WITH ANALOG FUEL QUANTITY ú 28-41-00
INDICATORS ú CONFIG 3 ú 01A Page 516 (BARFIELD SYSTEM TESTER) ú Nov 12/99
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
S 975-042-003
(4) Measure the empty tank capacitances.
(a) Push the PRESS TO MEASURE switch on the system test unit and hold it.
(b) Turn the TANK CAP PF thumbwheels until the meter shows the minimum value.
NOTE:____ If you turn the thumbwheels to a position farther than the correct position, the value on the meter increases.
(c) Turn the D.F. CONTROL knob until the meter shows the minimum value.
NOTE:____ If you turn the knob to a position farther than the correct position, the value increases. The D.F. CONTROL has very little effect for capacitances below approximately 50 pF. The test unit is more sensitive to adjustment of the D.F. CONTROL for larger capacitances.
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