HP 8560A, Service Manual

Page: 332 / 450

5. Compare the signals at the following test points with those illustrated in Figure 9-2.
X A2J202 pin 14
Y pin 3
Z OUT: 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.
3 . 0 0 0 . 0 0 v 1 . 0 0
0 . 0 0 0
Y
z
B L A N K
Figure 9-2. Line Generator Output Waveforms
Blanking
See function block J of A2 Controller Schematic Diagram (sheet 1 of 4) in the
Component-Level Information binder.
1. Using an oscilloscope, check for blanking pulses at pin 15. pin 6 should be
at a TTL high. Blanking pulses turn the CRT beam off during the sample time of the line
generators and when moving the CRT beam to a new position for drawing the next vector.
2. Set an oscilloscope to the following settings:
Amplitude Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Amplitude Offset
. . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . V
Sweep Time . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . 20
Triggering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..External
3. Externally trigger the oscilloscope off the signal at pin 8 (LBRIGHT).
Controller Section 9-5