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Maintenance— 2440 Service
Table 6-6 (cont)
Test 1. 10100101 is loaded and read back via U 243. Test result is set to fail if not a match on bits 0
through 5.
Test 2. 01001011 is loaded and read back via U 243. Test result is set to fail if not a match on bits 0
through 5.
Test 3. 10010110 is loaded and read back via U 243. Test result is set to fail if not a match on bits 0
through 5.
Test 4. 00101101 is loaded and read back via U 243. Test result is set to fail if not a match on bits 0
through 5.
Then M ODECON is set to 00010000 to select the top half of U 140 and the pattern is shifted left 2 bits.
YDIAG (U 141) bits 4, 5, 6, and 7 are tested, and the test result is set to FAIL if the test fails.
Test 1. 10100101 is loaded and read back via U 141. Test result is set to FAIL if not a match on bits 0
through 5.
Test 2. 01001011 is loaded and read back via U 141. Test result is set to FAIL if not a match on bits 0
through 5.
Test 3. 10010110 is loaded and read back via U 141. Test result is set to FAIL if not a match on bits 0
through 5.
Test 4. 00101101 is loaded and read back via U 141. Test result is set to FAIL if not a match on bits 0
through 5.
NOTE
OO through 0 4 = 0. Q4 through Q11 map to DO to D7. i.e., Q7
=
D3. By knowing which
test FAILS and the bit pattern one may easily determine the problem bit(s) (look for the bit
column in the failed tests that are the same).
If 2 or 3 tests fail, then there is a bus problem of some sort, and the busses must be exam ined. If all
four tests FAIL, then the problem can be in several locations.
1.
LDCOUNT might not be strobing the data into U 220 and/or U211 (Display Counters, schematic
diagram 17).
2.
Flip-flop U414A may not be resetting, or O R -gate U 323 pin 3 might be HI due to a failure.
3.
The busses into or out o f Address Multiplexers U 221, U 212, U 210 may not be operating properly.
4.
Readout Buffer U 140 may be defective.
Troubleshooting Procedure:
Set up the 2430 test scope as in Step 1 of the 2110 troubleshooting procedure.
Now using the CH 2 probe:
1.
Run test 2340 and verify the LDCOUNT strobe pulse at pin 11 of U 222, U 220, and U 211.
2.
Verify that after LDCOUNT strobe, that the outputs of Address Multiplexers U 222, U 220, U211
are stable and of the correct level for the test selected.
6-64
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 ...
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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 ...
Page 518: ...2440 Service ...
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