Tektronix 2440, User Manual

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M a in te n a n c e —2 4 4 0 Service
Table 6-6
2440 Troubleshooting P ro cedu res (cont)
4722 U644BT:
Check A12U664 pin 28 (Vcc) for a voltage in the range 4.75 V to 5.25 V (5% power supply accura­
cy). If voltage is below, problem is in the low-voltage power supply. Otherwise, if the voltage is
correct, then replace A12U664.
4723 U350BT:
Check A12U350 pin 28 (Vcc) for a voltage in the range 4.75 V to 5.25 V (5% power supply accura­
cy). If voltage is below, problem is in the low-voltage power supply. Otherwise, if the voltage is
correct, then replace A12U350.
5000 WP U470
Waveform
jji
P A12U470 (schematic diagram 2):
Testing Method:
The nature of these tests is such that all tests must be executed in order and may not be individually
executed. Therefore, any attempt to execute one test will result in all tests being executed.
The Waveform Processor test first sets all test results to NULL. Any failures will be fatal in terms of
instrument operation; however, the last test that was executed will be set FAIL and should help in
diagnosing the cause of the problem.
The Waveform p.P command memory has been checked out by this time as well as the bus struc­
ture that permits the System pP to control the Waveform pP bus.
5100 RUN-TASK Testing Method:
Loads a task into Command Memory U440 and tells the Waveform (xP to execute it. A 30 ms time­
out is executed; and then, INTREG (bit 0) is tested for WPDN. If it has not been set, the task did not
execute and terminate properly. If 5100 fails, it could be the Waveform Processor code ROMs, or the
Waveform pP itself (U470). In any event, the Waveform Processor Kernel tests will need to be run to
diagnose the source of the problem.
Troubleshooting Procedure:
Use the Waveform pP Kernel test in Procedure 8 to troubleshoot for a pP fault or a fault on the
Waveform pP address or data bus.
5200 BUSGRANT
Testing Method:
This test executes a bus request by setting bit D5 (pin 14) of PCREG U860 (schematic diagram 1)
HI, delaying 10 ms, and checking bit D6 of INTREG (Interrupt Register) U654 to see if a BUSGRANT
has occurred.
Troubleshooting Procedure:
Set up the 2440 test scope as in Step 1 of the 2110 troubleshooting procedure.
Run test 5200 in CONTINUOUS mode. Using the CH 2 Probe:
1. Check U860 pin 15 for LO-to-HI transition. If not occurring, replace U860.
2. Check U332D (schematic diagram 2) pin 13 for LO-to-HI transition. If not occurring, replace
Waveform pP U470.
3. Check U332D pin 11 for LO-to-HI transition. If not gating, replace OR-gate U332.
6-82
REV JU N 1991