TB 9-6625-2316-35
(10) Set POWER switch to OFF.
(11) Remove the A3 measurement circuit card, insert the extender card, then insert
measurement card on to the extender card.
(12) Gain Setting for IR Tests. In IR tests, the gain of the instrumentation
amplifier U64 (INA 101SM) is set at 40. With system power off, adjust R50 so that the
total resistance between pin 4 and pin 1 of U64 is 1025.6Ω (R).
(13) Gain Settings for Crosstalk Tests. In crosstalk tests, the detected crosstalk
signals are magnified by 17.78 times (equivalent to 25 dB) and then compared with the
exciting signals. The gain of the instrumentation amplifier U31 (INA 101SM) is set by
adjusting R20. With the system power off, adjust R20 so that the resistance between pin 1
and pin 4 of U31 is 2383.9Ω (R).
(14) Crosstalk Stimuli Waveform Adjustments. The crosstalk test stimuli (1000
U55 (MC54HC4060J) output, which is 1000 Hz square wave. It goes througoh a wave-
shaping circuit to become a trapezoidal wave then througoh an active filter circuit to
provide sine wave stimuli. R30 is the potentiometer used to shape the trapezoidal wave so
adjusting the trapezoidal waves.
(a) Turn on the system power and set the FUNCTION switch to XTALK.
(b) Observe the wave form at pin 1 of U55. Note that a 1000 Hz square wave is
observed.
(c) Observe the waveform at pin 14 of U35.
Note that the waveform is a
trapezoidal wave (1000 Hz).
(d) Adjust R30 so that the wave has 0.167 ms wide flat top (or flat bottom) (R).
(e) Check for sine wave at pin 6 of U 15 and its complementary sinewave at pin
6 of U16.
(15) When the procedures are completed, turn off the system power, remove the
extender card/cable, and insert the measurement card back into the card cage.
12. Final Procedure
a. Deenergize and disconnect all equipment.
b. Annotate and affix DA label/form in accordance with TB 750-25.
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