TM 11-6625-3145-14
Maintenance: Troubleshooting-318/338 Service
When the MPU writes at I/O address E0
hex
the WR and CS signals are sent to U070 (DAC V1) to latch the data. WR and
CS for U080 (DAC V2) are caused by the MPU’s access at I/O address E1
hex
. The WR signal is delivered from U150C
(quadruple 2-input positive NOR gate, 74LS02) on the A05 board, which comes from U214 (octal buffer/line driver with tri-
state output, 74LS240) on the A06 board. CS for these DACs are generated by U092B (dual 2-line to 4-line
decoder/demultiplexer, 74LS139) on the A05 board.
A number less than 80
hex
programs the DAC for positive output, and a number more than 80
hex
progarms it for negative
output centered on GND (80
hex
) in 0.1V steps. The actual output of these DACs is 1/4 of that specified in the Threshold
menu.
The settings and expected data are shown in Table 7-24.
Table 7-24
338 THRESHOLD TEST DATA VALUES
V1
V2
V3
Expected
+0.3V (83
hex
)
- 0.1 V (7F
hex
)
+ 0.2V
1
+0.7V (87
hex
)
-0.5V (7B
hex
)
+0.2V
1
+1.1V (8B
hex
)
- 0.9V (77
hex
)
+ 0.2V
1
+1.9V (93
hex
)
-1 .7V (6F
hex
)
+ 0.2V
1
+3.5V (A3
hex
)
-3.3V (5F
hex
)
+0.2V
1
+6.7V (C3
hex
)
-6.5V (3F
hex
)
+0.2V
1
-0.3V (7D
hex
)
+0.1V (81
hex
)
--0.2V
0
-0.7V (79
hex
)
+0.5V (85
hex
)
-0.2V
0
-1.1V (75
hex
)
+0.9V (89
hex
)
-0.2V
0
-1.9V (6D
hex
)
+1.7V (91
hex
)
-0.2V
0
-3.5V (5D
hex
)
+3.3V (A1
hex
)
-0.2V
0
-6.7V (3D
hex
)
+6.5V (C1
hex
)
-0.2V
0
V3 is calculated by (V1 + V2)/2 using two resistors, R 110 and R1 15 (4.99 K
Ω
) on the A05 board. V3 is selected by U1 14
(differential 4-channel multiplexer, 4052BP) on the A04 board and sent to U216 (ultra fast dual comparator, SP9687) and
the Comparator U232 (dual comparator, uPC393C) on the A02 Input-B board through the A08 board. In the A02 board,
V3 is compared with ground by the U232 Comparator and its output is sent to U252B (quad 2-input NOR gate, 10102) on
the A02 board. U252B is enabled by U234 (hex D master-slave flip-flop, 10176) on the A02 board when the MPU writes
X0XXXX
binary
into it at I/O address 03
hex
. U252B (10102) on the A02 board outputs the Threshold TEST signal to U144
(quad 2-input multiplexer, 10158) on the A04 board via the A08 board.
7-120
Summary of Contents for 318
Page 119: ...318 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 182: ...338 VERIFICATION AND ADJUSTMENT PROCEDURES ...
Page 253: ...318 ___________________ TROUBLESHOOTING TREES ...
Page 344: ...338 TROUBLESHOOTING TREES ...
Page 517: ...TM 11 6625 3145 14 318 338 4434 923 318 Block Diagram ...
Page 518: ...TM 11 6625 3145 14 318 338 4434 924 338 Block Diagram ...
Page 519: ...TM 11 6625 3145 14 318 338 4434 925 318 Acquisition Module Wiring Diagram ...
Page 520: ...TM 11 6625 3145 14 318 338 4434 926 318 338 Mainframe Wiring Diagram ...
Page 521: ...TM 11 6625 3145 14 318 338 4434 926 338 Acquisition Module Wiring Diagram ...
Page 522: ...TM 11 6625 3145 14 318 338 4434 928 Figure 9 1 318 A01 Input A Board Component Locations ...
Page 526: ...TM 11 6625 3145 14 ...
Page 528: ...TM 11 6625 3145 14 Figure 9 3 318 338 A03 ACQ Control Board Component Locations ...
Page 532: ...TM 11 6625 3145 14 ...
Page 536: ...TM 11 6625 3145 14 ...
Page 538: ...TM 11 6625 3145 14 ...
Page 539: ...TM 11 6625 3145 14 ...
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Page 541: ...TM 11 6625 3145 14 ...
Page 542: ...TM 11 6625 3145 14 Figure 9 8 318 338 A10 CRT Board Component Locations ...
Page 544: ...TM 11 6625 3145 14 Figure 9 9 318 338 A11 Inverter Board component Locations ...
Page 546: ...TM 11 6625 3145 14 Figure 9 10 318 338 A12 Regulator Board Component Locations ...
Page 551: ...TM 11 6625 3145 14 Figure 9 12 338 A01 Input A Board Component Locations ...
Page 553: ...TM 11 6625 3145 14 318 338 SERVICE ...
Page 554: ......
Page 555: ...PIN 058584 ...