ARMY TM 5-6675-308-34
MARINE CORPS TM 08837A-34/2
Table 4-11. CDU Testing and Troubleshooting Continued
Malfunction
Test procedure
Normal indication
indication/corrective action
2f. Press each CDU button and
TTY printout corresponds to push-
No or incorrect TTY printout:
observe TTY printout
button pressed
Example: CDU KEY DIST
Replace keyboard and control
circuit card assembly A3; check
wire harness continuity from P 1;
replace front panel assembly
Measure voltage between K1-X1
(+lead) and KI-X2 (-lead). If
greater than +20V: Check C 1;
replace K1. If less than +20V:
Check CR1; check continuity
between K1-XI and J1-39 and
K1 -X2 and XA01 -77; replace
display logic circuit card A 1
Pushbutton backlight does not light
at full bright intensity: Set display
intensity to full bright and measure
voltage between P1 -20 and PI -21
If greater than 105 VAC, replace
front panel assembly. If less than
105 VAC, measure voltage between
K1-X1 (+lead) and KI-X2 (-lead).
If greater than +20V, replace
display logic circuit card Al. If
less than +20V, check:
Kl; R1; continuity between J 1-35
and P1-21, E017 and P1-20, and
J1-20 and K1-B2. Repair as
necessary
NOTE
NOTE
comes out HA on TTY. "TAZ" CDU LAMP will not print out.
does not print. "OFF" does not print.
2g. Press CDU LAMP button and
Same as step 2e for first 2 seconds.
Intensity does not vary:
hold. Release LAMP pushbutton
Display then blacks out and slowly
increases in intensity in 9 steps
control to hold desired display
Replace computer power supply
brightness level
(approximately 1 see/step)
Audible alarm does not sound:
Measure voltage between EO 15
(+lead) and E014 (-lead). If it is
about +5V momentarily during
each intensity cycle, replace
audible alarm. If not, check con-
tinuity between EO 14 and XA02-77
and E015 and J1-10. Repair as
required. Replace display logic
circuit card A2
4-75
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