Chapter 9 475
Controller Section
Display Problems (8560E)
Display Problems (8560E)
NOTE See page page 621 for information on troubleshooting 8560EC display
problems.
Line Generators
Refer to function blocks D and I of A2 controller schematic diagram
(sheet 1 of 4) in the
HP 8560 E-Series Component Level Information.
The line generators convert the digital display information to an analog
output suitable to drive the A17 CRT driver assembly. These circuits
change the digital words into vectors, or lines, which move the beam of
the CRT. The vectors are each 6 µs long (width of the INTEGRATE
pulse) followed by a 1 µs SAMPLE pulse. When characters of text are
being drawn, the vectors are 3 µs long.
1. On the HP 8560E press
PRESET.
2. On the HP 8560E, press
CAL, MORE, and CRT ADJ PATTERN. If the
display is blank, press the bottom softkey and then the top softkey.
3. Set an oscilloscope to the following settings:
Amplitude scale ........................................................3V/div
Sweep time ............................................................. 1ms/div
Triggering ..............................................................External
4. Externally trigger the oscilloscope off the signal at A2U207 pin 8
(LBRIGHT).
5. Compare the signals at the following test points with those
illustrated in Figure 9-2 on page 476.
X POS: A2J202 pin 14
Y POS: A2J202 pin 3
Z OUT: A2J201 pin 3
BLANKING: A2J202 pin 15
NOTE Waveforms displayed on an analog scope may show considerably more
spikes. This is normal and is due to the wider displayed bandwidth.
6. Troubleshoot the circuits associated with any bad waveforms.
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