6-57
4. Check U243 pins 1 and 19 for the XDIAG pulse after clock pulse to U441. If ok, replace U243; if
not present, replace U550 (schematic diagram 17).
3. Select one pattern and check each output relative to the REF1 clock pulse for the proper level for
that bit/pattern. If incorrect, replace U441.
2. Check U441 pin 11 (TCURS) for clock activity (save to REF1 and display for timing).
1. Check U441 pin 1 to be LO (TCURSEN).
If test
=
FAIL for all test then look for failure using the following steps:
Troubleshooting Procedure:
If run from this level, all four tests are selected in turn, or one may execute anyone test by selecting
2321 to 2324. The test involves writing four unique patterns (see test 2200) to U441 and reading them
back from U243. The four patterns test for all stuck-at(s) and for lines shorted to other lines. By know-
ing which test fails and the bit pattern, one may easily determine a bus problem by observing which
bits are the same in the failed tests.
The TCURS test checks two ICs; U441 is a latch and the read back is Diagnostic Buffer U243. The
test result is set to PASS, any failure sets it to FAIL.
Testing Method:
Time Cursor Register All U441 (schematic diagram 16):
2320
TCURS
4. 'Check U141 pins 1 and 19 for the YDIAG pulse after the clock pulse to U241. If ok, replace U141.
If not present, replace U550 (schematic diagram 17).
3. Select one pattern and check each output relative to the REF1 clock pulse for the proper level for
that bit/pattern. If incorrect, replace U241.
2. Check VCURS clock to U241 at pin 11 for activity (save to REF1 and display for timing).
1. Check U241 pin 1 to be LO (VCURSEN).
If test
=
FAIL for all tests then look for failure using the following steps:
Troubleshooting Procedure:
If run from this level, all four tests are selected in turn, or one may execute anyone test by selecting
2311 to 2314. The test involves writing four unique patterns (see test 2200) to U241 and reading them
back from U141. The four patterns test for all stuck-at(s) and for lines shorted to other lines. By know-
ing which test fails and the bit pattern, one may easily determine a bus problem by observing which
bits are the same in the failed tests.
The Volts Cursors Register test checks two components; latch U241 readback is via Diagnostic Buffer
U141. The test result is set to PASS, any failure sets it to FAIL.
Volts Cursors Register A11U241 (schematic diagram 16) Testing Method:2310
VCURS
Table
6-6
(cont)
Maintenance-2430 Service
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