(c)  
Advance either engine thrust lever full forward.

(d)  
Move stabilizer in leading edge up (airplane nose down) direction. Check that warning horn sounds when dimension B is within the range for horn sounding (Table 1, Detail C, Fig. 502) for upper switch. Use trammel bar to measure dimension B, as shown. If horn does not sound within the required range of dimension B, adjust upper takeoff warning switch as follows: 1) Open LIGHTS and AURAL WARN circuit breakers on P6 panel. 2) Set dimension B as required for switch adjustment in Table 1 (Detail C). 3) Loosen but do not remove locknut securing switch arm to switch.

CAUTION:  IF LOCKNUT IS NOT LOOSENED, DAMAGE TO WORM GEAR MECHANISM CAN OCCUR DURING ADJUSTMENT.
4)  Loosen worm gear locking screw, and turn worm gear on opposite side until
switch actuates. 5) Tighten and lockwire worm gear locking screw; then tighten locknut. 6) Close LIGHTS and AURAL WARN circuit breaker on P6 panel.
(e)  Move stabilizer in leading edge down (airplane nose up) direction. Check that warning horn sounds when dimension B is within the range for horn sounding (Table 1) for lower switch. Use trammel bar to measure dimension B, as shown. If horn does not sound within the required range of dimension B, adjust lower takeoff warning switch in same manner as upper takeoff warning switch in previous step.
501 
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(5)  Adjust speed brake arming switch (S276) and takeoff warning switch (S129) (Detail D, Fig. 502), as applicable.
NOTE:  Takeoff warning switch (S129) is not installed on all airplanes (See Detail D for effectivity). When installed, it is adjusted in the same way as the arming switch, which is installed on all airplanes.
The takeoff warning and arming switches are installed with common attachment screws and actuated by common cam. On some airplanes, an autobrake off ramp switch (S585) is also installed with the same common screws, but actuated by a different cam. Check adjustment of the other switches if attachment screws are loosened.
(a)  
Place speed brake control lever in ARMED position so that lever arm roller is centered in ARMED detent on cam.

(b)  
Open lower nose compartment access door and locate switches.

(c)  
Place 0.18-inch thick feeler gage between switch actuator roller and cam on speed brake quadrant. Check that continuity does not exist between common and normally closed contacts of takeoff warning and arming switches.

(d)  
Place 0.08-inch thick feeler gage between switch actuator roller and cam. Check that continuity exists between common and normally closed contacts of takeoff warning and arming switches.

(e)  
Adjust switch as necessary to meet actuation requirements. Bend switch tab + 1/4 degree, if necessary. Ensure that switch attachment screws are tightened.

(f)  
Return speed brake lever to down position.

(g)  
Close lower nose compartment access door.

(6)  Adjust Takeoff Warning Switch S651 (Detail D, Fig. 502, Sheet 4)
(a)  
Open circuit breaker LANDING GEAR LIGHTS on panel P6.

(b)  
Disconnect electrical wiring from switch terminals.

(c)  
Place speed brake lever in DOWN position.

(d)  
Loosen attachment fasteners and lower switch until clear of lever mounted switch actuator.

(e)  
Connect ohmmeter across terminals C and NC of switch and check that switch is not actuated (continuity through switch).

(f)  
Adjust switch upward against lever mounted switch actuator until switch actuates (no continuity through switch).

(g)  
Tighten attachment fasteners.

(h)  
Remove ohmmeter and connect electrical wiring to switch terminals.

(i)  
Close circuit breaker LANDING GEAR LIGHTS on panel P6.

Jun 20/89  31-26-0
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.

(7)  Adjust Autobrake Off Ramp Switch S585 (Fig. 502, Sheet 4), as applicable.
NOTE:  The autobrake off ramp switch S585 is not installed on all airplanes. It is installed by common fasteners with the speed brake arming switch S276 and, on some airplanes, takeoff warning switch S129. If adjustment screws are loosened, check adjustment of other switches.
(a)  
Check that switch attachment screws are tightened.

(b)  
Set speed brake lever to DOWN position.

(c)  
Connect ohmmeter across terminals C and NO of switch and check for continuity between switch terminals.

(d)  
Move speed brake lever aft and check that open circuit between switch terminals is obtained when speed brake lever is 3.28 to 3.84 inches aft from DOWN position.
　
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