6-60
2. Verify that after LDCOUNT strobe, that the outputs of Address Multiplexers U222, U220, U211
are stable and of the correct level for the test selected.
1. Run test 2340 and verify the LDCOUNT strobe pulse at pin 11 of U222, U220, and U211.
Now using the CH 2 probe:
Set up the 2430 test scope as in Step 1 of the 2110 troubleshooting procedure.
Troubleshooting Procedure:
4. Readout Buffer U140 may be defective.
3. The busses into or out of Address Multiplexers U221, U212, U210 may not be operating properly.
2. Flip-flop U414A may not be resetting, or OR-gate U323 pin 3 might be HI due to a failure.
1. LDCOUNT might not be strobing the data into U220 and/or U211 (Display Counters, schematic
diagram 17).
If 2 or 3 tests fail, then there is a bus problem of some sort, and the busses must be examined. If all
four tests FAIL, then the problem can be in several locations.
NOTE
00 through 04
=
O.04 through 011 map to 00 to 07. i.e., 07
=
03. 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).
Test 4. 00101101 is loaded and read back via U141. Test result is set to FAIL if not a match on bits 0
through 5.
Test 3. 10010110 is loaded and read back via U141. Test result is set to FAIL if not a match on bits 0
through 5.
Test 2. 01001011 is loaded and read back via U141. Test result is set to FAIL if not a match on bits 0
through 5.
Test 1. 10100101 is loaded and read back via U141. Test result is set to FAIL if not a match on bits 0
through 5.
Then MODECON is set to 00010000 to select the top half of U140 and the pattern is shifted left 2 bits.
YDIAG (U141) bits 4, 5, 6, and 7 are tested, and the test result is set to FAIL if the test fails.
Test 4. 00101101 is loaded and read back via U243. Test result is set to fail if not a match on bits 0
through 5.
Test 3. 10010110 is loaded and read back via U243. Test result is set to fail if not a match on bits 0
through 5.
Test 2. 01001011 is loaded and read back via U243. Test result is set to fail if not a match on bits 0
through 5.
Test 1. 10100101 is loaded and read back via U243. Test result is set to fail if not a match on bits 0
through 5.
Table
6-6
(cont)
Maintenance-2430 Service
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