Diagnostic Testing and Troubleshooting
Troubleshooting the Instrument
5
5-31
8.
If a segment under each of several (or all) grids fails to be turned on (or off)
properly, one of the anode drive signals may not be connected properly from A2U1
to A2DS1. When an anode signal is at Vcc, and a grid signal is at Vcc, the
corresponding segment on the display is illuminated.
9.
If the Microprocessor has difficulty recognizing front-panel button presses, the
switch scanning signals SWR1 through SWR6 should be checked. When no switch
contacts are being closed, the switch scanning lines should have about 20 k
Ω
of
resistance between each other (through two 10 k
Ω
pull-up resistors to Vcc). Unless
one of the switches is closed, none of the switch scanning lines should be shorted
directly to GND at any time.
Variations in the Display
5-29.
Under normal operation, the display presents various combinations of brightly and dimly
lit annunciators and digits. However, you may encounter other, random irregularities
across different areas of the display under the following circumstances:
•
After prolonged periods of displaying the same information.
•
If the display has not been used for a prolonged period.
This phenomenon can be cleared by activating the entire display and leaving it on
overnight (or at least for several hours). Use the following procedure to keep the display
fully lit:
1.
With power OFF, press and hold the left arrow key, then press power ON.
2.
Wait a moment for the instrument to beep, then release the key. The entire display
will now stay on until you are ready to deactivate it.
3.
At the end of the activation period, press any button on the front panel; the
instrument resumes the mode in effect prior to the power interruption (Active or
Inactive.)
A3 A/D Converter PCA Troubleshooting
5-30.
The following paragraphs provide troubleshooting hints for the A3 A/D Converter PCA.
Use this material in conjunction with Chapter 2, “Theory of Operation.”
WARNING
To avoid electric shock, disconnect all channel inputs from the
instrument before performing any troubleshooting operations.
Summary of Contents for NetDAQ 2640A
Page 14: ...NetDAQ Service Manual x...
Page 46: ...NetDAQ Service Manual 2 4...
Page 106: ...NetDAQ Service Manual 2 64...
Page 108: ...NetDAQ Service Manual 3 2...
Page 164: ...NetDAQ Service Manual 4 42...
Page 206: ...NetDAQ Service Manual 6 2...
Page 218: ...NetDAQ Service Manual 6 14 2645A 1601 Figure 6 2 A1 Main PCA Assembly...
Page 220: ...NetDAQ Service Manual 6 16 2620A 1601 Figure 6 3 A2 Display PCA Assembly...
Page 230: ...NetDAQ Service Manual 6 26 2645A 1603 Figure 6 5 2645A A3 A D Converter PCA Assembly...
Page 234: ...NetDAQ Service Manual 7 2...
Page 242: ...2640A 2645A Service Manual 7 10 Figure 7 2 A2 Display PCA Assembly 2620A 1602...
Page 243: ...Schematic Diagrams 7 7 11 Figure 7 2 A2 Display PCA Assembly cont 2620A 1002...
Page 251: ...Schematic Diagrams 7 7 19 2645A 1603 Figure 7 4 2645A A3 A D Converter PCA Assembly 2645A 1603...
Page 258: ...2640A 2645A Service Manual 7 26 Figure 7 5 A4 Analog Input PCA Assembly 2620A 1604...
Page 260: ...2640A 2645A Service Manual 7 28...