Texas Instruments 990 Manual page 121

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945424-9701
Step
2
3
Table 2-S. VDT Controller Troubleshooting Procedure
Procedure
Install VDT controller into
hot mock-up system.
Apply power to hot mock-up
system.
Load and execute diagnostic.
Normal Indication
Blank CRT screen
Test LED off
Sync(s) LED on rear of
display unit lighted.
Dark margin around
raster of horizontal lines
which appear fixed in
position. Bright, angular
retrace. Dark margin
may not appear surround
raster.
Clock oscillator frequency
=
11 .004 MHz.
No error messages
2-19
If Abnormal
Perform step 1, table 2-6.
Perform step 2, table 2-6.
Perform step 3, table 2-6.
Perform step 4, table 2-6.
Perform step 5, table 2-6.
Proceed to tables 2-7
through 2-14.
Digital Systems Division