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Monitor Fault Isolation
Procedures
Have the monitor sync-locked to a signal, if possible,
before starting this procedure.
Always reference the DVM or oscilloscope to DC (cold)
ground unless instructed otherwise.
A 10X probe is recommended for use with the oscillo-
scope.
1. With a DVM, measure the voltage at pin 2 of con-
nector 3V3 on the main board (see Figure 4-11).
If + 150 VDC is present, proceed to step 2.
If + 150 VDC is not present, replace the main
board.
2. With a DVM, measure the voltage at pin 2 of con-
nector 3F3 on the main board.
If the voltage is from + 4.5 VDC to + 12 VDC,
proceed to step 3.
If the voltage is less than + 4.5 VDC, replace the
main board.
3. With a DVM, measure the voltage at pin 2 of con-
nector 3D3 on the main board.
If the voltage is from + 12 VDC to + 26 VDC, pro-
ceed to step 4.
If the voltage is more than + 26 volts, replace the
main board.
Page
4-4
4. With a DVM, measure the voltage at pin 2 of con-
nector 3G3 on the main board. A value of + 0.3
VDC should be observed. Observe this point with
an oscilloscope and verify the presence of horizon-
tal drive pulses.
If the pulses are present, proceed to step 5.
If the pulses are not present, replace the main
board.
5. With an oscilloscope, measure the supply voltages
at connector 3D3 on the main board. The voltages
should be:
Pin 1
Pin2
Pin3
PinS
Pin6
170 volts peak-to-peak
+26 volts DC
Ground
60 volts peak-to-peak
140 volts peak-to-peak
If all voltages are correct, proceed to step 6.
If any voltage is not correct, replace the sweep
assembly.
6.
Use a high voltage probe to verify the presence
of 26 kV on the CRT anode lead.
If + 26 kV is present, proceed to step 7.
If + 26 kV is not present, replace the sweep as-
sembly.
7. Apply a white field on the entire CRT. This can
be done with a video source or, with a Z-100 or
Z-100 PC computer, by using the Z-BASIC or GW-
BASIC command:
PAINT (0, 0)" 7
Servicing
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