6-73
4. Check the data
1/0
pins U432 (pins 9,10,11,13,14,15,16,17) for activity. If no activity (stuck HI
or LO) when output enable is LO, suspect U352; otherwise suspect U432.
Using the CH 2 probe:
2. Check for activity on the write enable line of U432 (WRR, pin 21), and note that it is LO at the
same time as the chip select signal. If no activity, work backwards through U5428 and find the
problem.
3. Check for activity on the output enable line of U432 (WRD, pin 20). If not active, work backwards
through U5428 and find the problem.
1. Check for activity on the chip select line of U432 (pin 18), and trigger the scope on the signal if
active. If no activity, work backwards through U250D and find the problem.
Using the CH 1 probe:
Run test 3810 in CONTINUOUS mode.
If test
=
FAIL then look for failure and correct, using the following steps:
Troubleshooting Procedure:
NOTE
If tests 3400, 3700, and 3800 a/l fail, the most likely faults are: a stuck data line to
Waveform Data Buffer
A
12U352, a bad select signal to
A
12U352, or Buffer
A
12U352itself.
COEFFICIENT RAM A12U432 (schematic diagram 2):
3800
A12U432
4. Check the data
1/0
pins of U440 (pins 9,10,11,13,14,15,16, and 17) for activity. If no activity
when output enable is LO, then suspect U352; otherwise check U440.
3. Check for activity on the output enable line of U440 (WRD, pin 20). If not being enabled, work
backwards through U5428 to find the problem.
2. Check for activity on the write enable line of U440 (WRR, pin 21), and note that it is LO at the
same time as the chip select line. If no activity, work backwards through U5428 and find the
problem.
Using the CH 2 probe:
1. Check for activity on the chip select line to A12U440 (pin 18), and trigger the scope on the signal if
active. If no activity, work backwards through U250C and find the problem.
Using the CH 1 probe:
Run test 3710 in the CONTINUOUS mode.
If test
=
FAIL then look for failure and correct, using the following steps:
Troubleshooting Procedure:
Table 6-6 (cont)
Maintenance-2430 Service
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