Document 9913
Rev. V
Instruction Manual
Style 3
Runway Centerline Light L-850A & Touchdown Zone Light L-850B
8
9.6
Lens Replacement
If a lens is broken, leaks or is badly pitted or scarred, it must be replaced. It is highly recommended that this
task be performed in a clean shop environment. Use Lens Replacement Kit P/N 21126-C for clear lenses, and
kit P/N 21126-R for red lenses.
Remove and secure power to the fixture.
Separate the Optical Assembly
from the outer ring by removing the two bolts. There are two pry slots in the optical housing to help separate the
Optical Assembly from the support ring. Turn the Optical Assembly upside down and remove the four screws
holding the inner cover to the light housing. Remove the two lens retaining bracket screws from the light housing.
Remove the lens-retaining bracket and discard the lens-retaining gasket. Firmly push the lens/boot assembly from the
outside of the light housing; discard the old lens and boot. Thoroughly clean the lens opening with denatured alcohol
and allow to dry. Inspect the lens opening for scratches or pits, a damaged lens opening surface will not seal properly.
Place a new lens boot (P/N 21103) over the replacement lens (P/N 21102-C or 21102-R). Apply a thin coat of
Dow Corning FS 1292 grease over the entire outside surface of the lens boot. Align the lens/boot assembly in
the lens opening and press it into place. Verify that the lens boot is not pinched in the lens opening. Using a new
lens retaining gasket (P/N 21101), fasten the lens retaining bracket (P/N 21100) to the light housing. Torque the
mounting screws to 55-60 in-lbs. Assembly the inner cover onto the light housing. The screw hole patterns in
the inner cover and light housing are offset to insure proper alignment. Torque the mounting screws to 30 in-lbs.
Perform a pressure test per paragraph 9.8. Clean the mounting flange area of the support ring. Place the Optical
Assembly into the support ring. Secure per section 8.2
9.7
Feed-thru Replacement
Remove and secure power to the fixture.
Separate the Optical Assembly from the outer ring by
removing the two bolts. There are two pry slots in the optical housing to help separate the Optical Assembly
from the support ring. Turn the Optical Assembly upside down and remove the four screws holding the inner
cover to the light housing. Disconnect the lamp leads from the feed-thru terminals. Remove the feed-thru by
unscrewing the retaining collar. Clean the mounting surface with Isopropyl Alcohol and allow to dry. Apply a
thin coat of Dow Corning FS 1292 grease to the mounting flange of a new feed-thru (P/N 21121 for 2 lamp/ 1
plug, or P/N 21122 for 1 lamp/ 1 plug). Apply a drop of Loctite 242 to the feed-thru adapter threads. Screw the
feed-thru retaining collar onto the adapter; refer to Figure 6 for proper inner cover/ feed-thru orientation. Torque
the retaining collar to 30 in-lbs. Assembly the inner cover onto the light housing. The screw hole patterns in the
inner cover and light housing are offset to insure proper alignment. Torque the mounting screws to 30 in-lbs. .
Perform a pressure test per paragraph 9.8. Clean the mounting flange area of the support ring. Place the Optical
Assembly into the support ring. Secure per section 8.2
9.8
Pressure Test
A light fixture should be subjected to a 20-psi air pressure test to verify that it is waterproof whenever it has
been opened or components have been replaced. A tire valve style pressure fitting is located on the bottom of
the inner cover. Pressurize the fixture to 20-psi then place it in a tub of water or use a soap solution to locate
escaping air bubbles. Carefully inspect the areas around the lens, inner cover seal, and feed-thru adapter for
leaks. Relieve the internal air pressure before installing the fixture or attempting to repair a leak.
