TM 1-6625-476-30
2-5
2-6. TEST DESCRIPTION. (CONT)
i.
SYSTEM INTENSITY TRANSFER FUNCTION NFOV (SITN), MFOV (SITM), AND WFOV (SITW)
TESTS.These are depot level tests. They check the FLIR ratio or output video signal to input signal
video signal to input thermal signal in all three FOV with the FLIR gain adjusted to maximum and
minimum. During these tests, control unit assembly 1A1 in the electronic station is programmed to 11
different temperatures to ensure that the TADS NSA can detect and follow these temperature changes. If
a test is out of tolerance, the operator is directed to perform channel balance.
j.
ELECTRO-OPTIC NOISE (EON) TEST. This is a depot level test. It checks the video output for dark
shading when an even temperature noise mask is used. If the test fails, you are directed to perform
channel balance. Note that you should run this test when the AVUM work request and supporting
documents have identified a TADS NSA as having excessive noise or dark shading problems.
k. CHANNEL BALANCE TEST. This procedure is used to detect dead or noisy channels on the video
monitor. Routines built into the procedure direct you to perform replacements and/or adjustments as
necessary. Perform channel balance as follows:
(1)
Perform the full channel balance on all 180 channels when cooler/dewar A29/A30 has been
replaced.
(2)
Perform a partial channel balance on affected channels when dead or noisy channels have
been identified on the video monitor. Also perform a partial channel balance when preamplifier or
postamplifier CCAs have been replaced or moved.
Channel balance will only pass if the first and last channels adjusted are good channels. The program
will keep track of any bad channels that are encountered during adjustment, and will provide applicable
replacement instructions.
2-7. PRETESTING DATA.
Awareness of the following information will help you to successfully test the TADS NSA, and may
prevent unnecessary termination of the test.
a. Noise. When power is applied to the scanner assembly and cooler/dewar assembly, they make a
considerable amount of noise. This is normal operation, and the program should not be terminated. Also,
the scanner assembly does not start at the same time as the cooler/dewar. This increases the operating
noise.
b. Lens Movement. During testing of the FOV assembly, the lens rotation is very quick and slams into
the stop positions. This is normal operation and the program should not be terminated.
c. Test Program Delays. At times, the UUT test program will appear to have stopped for up to 20
minutes. This is because some portions of the program require this amount of time to execute. During
these times, a prompt will appear on the VDT explaining that a program delay is in progress.
d. Cables and Meter Leads. Avoid hanging cables or meter leads in back of the TADS NSA during
testing. They could get tangled in the optics assembly and damage to the TADS NSA could result.
