6-45
Check the ACQDN signal at A11U670 (Time Base Controller).
1. "Running Self Test" message is displayed, but nothing else is occurring.
Test 8000-plus
(+)
LED on and Self Test has halted.
Problem is probably in the Display State Machine circuitry (schematic diagram 17) or the DISON signal
path to the System JLPInterrupt circuit. Check that the DISON signal is correct at U414 pin 6
(waveform 126 on schematic diagram 17); if not, troubleshoot the Display State Machine (see NO
DISPLAY troubleshooting chart in the "Diagrams" section for typical Display State Machine
waveforms). If the DISON signal is ok, check the DISON signal path to U580 pin 4 for continuity.
Test 3000- TRIG and READY LEOs on or Test 6000-READY and ARM LEOs on, and the 2430 Self
Test has halted.
SYSTEM JLP
HALTS IN
POWER-UP
TEST
6. Check the DISON signal at U414A pin 6 and the PRESTART + DISPLAY signal at U323A pin 3
for correct operation (schematic diagram 17). If not correct, troubleshoot the Readout State
Machine (see the "No Display" troubleshooting tree at the back of this manual).
5. Check the suspected DAC outputs at the points indicated in the FORCE DAC test table. If DAC
outputs are ok, troubleshoot Intensity multiplexer A10U811 (schematic diagram 6) and its select
signals, and the Z-axis signal amplifiers (A1OU810 and A1OU812).Troubleshoot DAC circuit if the
DAC outputs are bad (see the DAC System troubleshooting procedure).
4. If the INTENSITY pot changes the DAC settings in the FORCE DAC test, the pot and pot-
scanning circuitry are ok; if not, troubleshoot the Front Panel.
3. Check the ZINT signal on pin 2 of U227. Does it vary correctly with the DISP INTENSITY control?
If yes, suspect U227. If no, then use the FORCE DAC test to verify the INTENSITY pot and the
DAC SYSTEM.
2. If the signal at U227 pin 13 does not vary with the DISP INTENSITY control, check CR135 for
open or short.
1. Check signal output of U227 at pin 13. Is the waveform correct (see waveform 145 on schematic
diagram 19), and does its amplitude vary with the DISP INTENSITY control? If yes, then check the
signal path components to the junction of CR442 and R546 for continuity.
No Intensity Control
8. If all ok in the crt and Z-Axis circuitry, go to the "No Display" troubleshooting tree at the back of
this manual. Also, check that the Power-on Self Test completes without hanging. (See "System
JLPHalts in Power-up Test" following "No Intensity Control.")
7. If ZON not present, troubleshoot the Z-Axis Logic circuitry, U223C and input gates and signals
(schematic diagram 17).
6. Check input to U227 ZON on pin 3. If input ok, check supply voltages to U227. If all ok, change
U227.
5. Does intensity vary with the Grid Bias Adjust? If not, troubleshoot the DC Restorer circuit. If it
does, check the signal from U227 at pin 13.
4. If crt voltages are good, and still no intensity, turn off the 2430 and check the crt heater for con-
tinuity from pins 1 to 14. If open, change the crt.
Table 6-6 (cont)
Maintenance-2430 Service
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