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HYDRA
Service Manual
5-30
While the instrument is scanning, check that data is being stored correctly. Use an
oscilloscope to monitor activity on the 7 outputs of the Byte Counter (A6U3) and the 11
outputs of the Page Register (A6U1 and A6U4). Since the repetition rate is fairly low, it
may be necessary to use a storage oscilloscope to capture the activity. If either of these
circuit elements is not functioning, check the Address Decode circuit (A6U2, A6U5,
A6U8) for activity at the end of every scan.
If the outputs of the Page Register and the Byte Counter are showing reasonable activity,
verify that these signals are also being received by the Nonvolatile Memories (A6U6 and
A6U7). Check CS*, WR*, and OE* inputs on A6U6 and A6U7 for proper activity.
There may also be a problem in reading data back from the Memory PCA. After
allowing the Memory PCA to fill with scan data ("F" annunciator on the display lit), turn
off scanning (press SCAN). Now press the LIST button and select the "StorE" entry in
the menu. While the Hydra is formatting and sending the Memory PCA contents to the
RS-232 interface, again monitor the circuit areas described above for reasonable voltage
levels and activity.