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Video (Signal) Only
If only the video information is incorrect, suspect A4 IF Section, A3A8, or A3A9. To
eliminate the IF, connect the rear-panel SWEEP and VIDEO RECORDER OUTPUTS to an
oscilloscope. If the video is correct, then either A3A8 or A3A9 is defective.
Remove cable 96 from A3A9Jl. Then jumper A3A8TPl to A3A9TP3 and push Instrument
Preset. This substitutes the sweep ramp for the video input. The CRT display is similar
to Figure 7 in the A3A8 tab. If the ramp is incorrect, remove A3A9, jumper A3A8TPl to
Troubleshooting procedure. If ramp is incorrect, suspect ADC on A3A8. See the A3A8
Troubleshooting notes to verify this.
Don't rule out the sweep system, especially the ramp converter on A3A8, when
troubleshooting video failures. Some ramp converter failures produce CRT displays that are
similar to those caused by ADC failures.
All CRT Information Blank or Distorted
Check X, Y, and Z DISPLAY OUTPUTS on rear panel. If these are correct, the fault is most
likely with the X/Y Deflection Amplifiers or Z Axis Amplifier (or AlA XYZ Deflection
Amplifier). The following program, which places a dot at the center of the display, is helpful
when troubleshooting the Deflection Amplifiers. It balances the voltages in both halves of the
circuitry. Press Instrument Preset and key in the following:
Blank Trace A, (%K), Recorder Lower Left, 0 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . .DSPL ADRS
1090 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vector Command
512 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..X coordinatesforcenter screen
512 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Y coordinates for center screen
1092 Hz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . End of display
If the X, Y, and Z DISPLAY OUTPUTS produce either distorted or no output, Digital
Storage must be tested. Connect a jumper from A3A6TP3 to A3A6TP6 and push A3A7Sl.
The Digital Storage Test Pattern (Figure 1 of the A3 Digital Storage Troubleshooting tab)
results. Refer to the Digital Storage Troubleshooting procedures. If the test pattern is correct,
start with the system ROMs check.
If the test pattern is incorrect, verify operation of A3A3 Line Generator and A3A2 Intensity
Control. Refer to the troubleshooting information included with the schematics. If A3A3 and
Whenever the display is blank, and the left INSTR CHECK LED is off, check the AlA
Regulator. The power supply LEDs indicate the presence of voltage but not regulation. Verify
operation of A3A2 Intensity Control and AlA Z Axis Amplifier. If these are all working
properly, carefully examine the AlA High Voltage Regulator assembly.
If the CRT is blank, check the CRT oscillator to see if it is turned off. Measure AlA6TP6
with a DVM. If TP6 is a digital high, the CRT will not operate since the oscillator is turned
off. Troubleshoot AlA to check for bad components, shorts, and so forth. If the AlA is
operating correctly, check the CRT disable line from A4A9U14. If the IC is damaged, it
2
Al
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