3-4
GTX 327 MAINTENANCE MANUAL
Rev B
190-00187-05
Table 3-2. Key Matrix Test
ACTIVE
ROW
OUTPUT
INPUT COLUMN ASSIGNMENT
KEY COL 1
(R218)
KEY COL 2
(R219)
KEY COL 3
(R220)
KEY COL 4
(R221)
KEY COL 5
(R222)
KEY ROW 1
(J103-16)
1
2
6
START/STOP
NOT USED
KEY ROW 2
(J103-17)
0
3
7
CLR
NOT USED
KEY ROW 3
(J103-18)
VFR
4
\/ 8
FUNC
NOT USED
KEY ROW 4
(J103-19)
IDENT
5
/\ 9
CRSR
NOT USED
Perform the following tests with reference to components on the main board. (Figure 3-2):
If the ON, STBY or ALT KEY fail, verify the following:
1.
D507-3 and Q302-3 go LOW when the ON key is pressed.
2.
D509-3 and Q302-3 go LOW when the STBY key is pressed.
3.
D508-3 and Q302-3 go LOW when the ALT key is pressed.
If the OFF KEY fails, verify the following:
4.
D506-3 goes LOW when the OFF key is pressed. Approximately 2 seconds later Q302-1 goes LOW.
If the DISPLAY DIMMING fails, verify the following:
5.
Verify the signal on Q501-4 has a 4 kHz pulse width modulation (PWM) as shown in figure 3-1.
TRACE 1: BACKLIGHT (Q501-4)
TRACE 2: KEY BACKLIGHT COMMON (Q501-5, -6)
Figure 3-1. 4 kHz PWM Signal on Q501
6.
Verify that as the display dims, the PWM duty cycle decreases.
The document reference is online, please check the correspondence between the online documentation and the printed version.