Tektronix 2440, Руководство пользователя

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Maintenance— 2440 Service
Table 6-6 (cont)
2310 Volts Cursors Register A11U241 (schematic diagram 16) Testing Method:
VCURS
The Volts Cursors Register test checks two components; latch U241 readback is via Diagnostic Buffer
U 141. The test result is set to PASS, any failure sets it to FAIL.
If run from this level, all four tests are selected in turn, or one may execute any one 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.
Troubleshooting Procedure:
If test = FAIL for all tests then look for failure using the following steps:
1. Check U241 pin 1 to be LO (VCURSEN).
2. Check VCU RS clock to U241 at pin 11 for activity (save to REF1 and display for timing).
3. Select one pattern and check each output relative to the REF1 clock pulse for the proper level for
that bit/pattem . If incorrect, replace U 241.
4. Check U141 pins 1 and 19 for the YDIAG pulse after the clock pulse to U 241. If ok, replace U141.
If not present, replace U550 (schematic diagram 17).
2320 Time Cursor Register A 11U441 (schematic diagram 16):
TCURS
Testing Method:
The TCU RS test checks two ICs; U441 is a latch and the read back is Diagnostic Buffer U 243. The
test result is set to PASS, any failure sets it to FAIL.
If run from this level, all four tests are selected in turn, or one may execute any one test by selecting
2321 to 2324. The test involves writing four unique patterns (see test 2200) to U441 and reading them
back from U 243. 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.
Troubleshooting Procedure:
If test = FAIL for all test then look for failure using the following steps:
1. Check U441 pin 1 to be LO (TCURSEN).
2. Check U441 pin 11 (TC UR S) for clock activity (save to REF1 and display for timing).
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 U 441.
4. Check U243 pins 1 and 19 for the XDIAG pulse after clock pulse to U 441. If ok, replace U243; if
not present, replace U550 (schematic diagram 17).
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