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Maintenance— 2440 Service
Table 6-6 (cont)
1.
LDCOUNT might not be strobing the data into Display Counters U220 and/or U211 (schematic
diagram 17).
2.
U414A may not be resetting, or U323 pin 3 might be HI due to a failure.
3.
Address Multiplexers U221, U212, and U210 may not be operating properly.
4.
Ramp Buffer U130 (schematic diagram 16) may be defective.
Set up the test scope as in Step 1 of the 2110 troubleshooting procedure.
Now using the CH 2 probe:
1.
Run test 2230 in CONTINUOUS mode and verify the LDCOUNT strobe pulse at pin 11 of U222,
U220, and U 211.
2.
Verify that after LDCOUNT strobe, that the outputs of U222, U220, and U 211 are stable and of
the correct level for the test selected.
3.
Verify that U323 pin 3 is LO.
4.
Verify the outputs of U221, U212, and U210 are stable and correct after the LDCOUNT strobe to
the previous bus.
5.
Verify the chip enable to U130 pins 1 and 15 is LO. If ok to here, replace U130.
2340
Readout Buffer U140 (diagram 16):
U140
Testing Method:
If run from this level, all four tests are selected in turn, or one may execute any one test by selecting
2341 to 2344.
This test requires the display state machine to be operative. There is no ‘‘good” way to insure that it is
functional and there have been no previous tests. Therefore, if this test fails, it could be for several rea
sons other than U140.
Initialization:
DISCON = 01100000. Significant bits are b2, b5, b6, and b7 (STOPDIS, enable " Q ” bus, not
ENVELOPE mode).
MODECON = 00001000. Significant bit is b3 (U140 lower half).
M ISC = 00100000. Significant bit is b5 (ZAXIS OFF).
The test result = PASS.
The test is to load a pattern into the display counters, U220 and U211, with the LDCOUNT strobe. The
counter outputs are switched to the Q bus through U221, U212, U210 by holding U414A in the reset
mode (PRESTART + DISPLAY is LO). The inputs to U140 (lower half) are the bits Q6 through Q8
where Q1 through Q3 = 0. Q4 and Q5 are the bO and b l data of the pattern. To read back properly,
one shifts the pattern left 3 bits and use bits 4, 5, and 6 of XDIAG (U243); the test result is set to FAIL
if the test fails.
6-63
Summary of Contents for 2440
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Page 91: ...Theory of Operation 2440 Service 3 49 Figure 3 5 Simplified CCD architecture ...
Page 120: ...Theory of Operation 2440 Service Figure 3 10 DC Restorer 3 78 ...
Page 130: ...Theory of Operation 2440 Service 3 88 ...
Page 136: ...Theory of Operation 2440 Service Figure 3 15 PWM Regulator and Inverter 3 94 ...
Page 138: ...Theory of Operation 2440 Service Figure 3 16 PWM switching waveforms 3 96 ...
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Page 423: ...2440 Service Figure 9 4b 2440 Block diagram part 2 6330 27 BLOCK DIAGRAM PART 2 ...
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Page 428: ...2440 Service WAVEFORMS FOR DIAGRAM 1 6 2 8 5 3 2 ...
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Page 432: ...2440 Service WAVEFORMS FOR DIAGRAM 2 BUS ISOLATED 6 6 0 3 4 9 ...
Page 433: ...WAVEFORMS FOR DIAGRAM 2 ...
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Page 450: ...2440 Service WAVEFORMS FOR DIAGRAM 8 6603 27 ...
Page 455: ...W A V EFO R M S FOR D IAG RAM 11 WAVEFORMS FOR DIAGRAM 11 6603 29 ...
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Page 471: ... C N i u i t e x r 4 j u J l i 1 i 6 28 5 44 WAVEFORMS FOR DIAGRAM 18 ...
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Page 512: ...A12 2440 Service F IG 3 C IR C U IT BOARDS ...
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Page 517: ...10 16 R E V J U L 1993 Replaceable Mechanical Parts ...
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