6-58
If 2 or 3 tests fail, then there is a bus problem of some sort and they must be examined. If all four
tests FAIL, then the problem can be in several locations.
NOTE
00 through 03
=
O.04 through 011 map to DO through D7; i.e., 04
=
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).
Troubleshooting Procedure:
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.
The test is to load a pattern into the display counters, U220 and U211, with the LOCOUNT strobe
(data loaded to U222 is fixed). Their outputs are selected by U221, U212, U210 holding U414A in the
reset mode and not PRESTART. Since the STOPDIS line is LO, the display counters are selected as
the source to the 0 bus (U210, U212, U221). The inputs to U130 are the bits
01..05
where
01..03
=
O. and
04,
05 are the bO, b1 data of pattern. To read back properly, shift the pattern left 3 bits and
use only the lower 5 bits of XDIAG (U243).
The test result
=
PASS.
MISC
=
00100000. Significant bit is b5 (ZAXIS OFF).
MODECON
=
00001000. Significant bit is b3 (U140 lower half).
OISCON
=
01100000. Significant bits are b2, b5, b6, and b7 (STOPDlS, enable
"0"
bus, not ENV
mode).
Initialization:
This test requires the display state machine to be operative. There is no "good" way to ensure that it
is functional, and there have been no previous tests to help to find that out. Therefore, if this test fails,
it could be for several reasons other than U130. If the power-on Self Test starts to run but halts at
test level 3000 or test level 6000 (as indicated by the lighted Trigger LEOs), the problem may be in the
Display State Machine circuit (schematic diagram 17) or the DISON signal path to the System ILPInter-
rupt circuit. Use the Display Troubleshooting Chart to troubleshoot the Display State Machine and
check that the DISON signal at U414 pin 5 is correct.
If run from this level, all four tests are selected in turn, or one may execute anyone test by selecting
2331 to 2334.
Testing Method:
Ramp Buffer A11U130 (schematic diagram 16):2330
U130
Table
6-6
(cont)
Maintenance-2430 Service
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