REV JUL 1987
6-41
2. The first and second bezel buttons are used to select through the DAC values to be tested. The
INTENSITY knob sets the values.
3. Test suspected DAC circuits for correct voltage limits over the control range using the test points
and values given in the following Force DAC Ranges table.
The SPECIALmenu choicesare normallydisabledto the user and press of the SPE-
CIAL menu button calls up the display"DISABLED-SEE MANUAL", To enable the
choices for servicing,the cabinet must be removed and Jumper A 13J156(EXT CAL
DIS on diagram
13)
must be removed.
NOTE
1. Press the SPECIAL menu choice under Extended Functions and then press FORCE DAC.
Force DAC Test
6. Use the FORCE DAC test to check suspected output ports for correct control range.
5. Check that only one DAC MUX enable at a time from U272 is LO.
4. If the levels at TP650 and TP660 are bad, check DAC multiplexer U651, the DAC inputs (U800
pins 1 through 12), and current-to-voltage converter U661. Should see U661 having an output of
32 dc levels, switching from one to the next each 2 ms, and then repeating. The maximum output
level is
±
1.36 V. This output signal should be present at the input to each of the DAC multi-
plexers (pin 3), and each multiplexer output pin should have a steady dc voltage level present.
3. If the test point voltages are good, the DAC SYSTEM is operating normally to this point. Trouble-
shoot the DAC multiplexers (U831, U821, and U830) and the individual DAC output ports
(schematic diagrams 5 and 6).
2. Check TP660 (also on the Main Board) for
+
1.25 V.
1. Check TP650 (found on the Main Board) for 0 V.
Symptoms are CCD and Peak Detectors gain fails SELF CAL, and Trig Level fails SELF CAL.
DAC System (schematic diagrams 5 and 6):
DAC SYSTEM
FAILURE
3. Verify that the flex connector at the back of the A12 board is installed correctly. If ok, then the
WORD RECOGNIZER probe is possibly defective. Try the probe on another 2430 to verify its
operation.
2. Select TRIG POSITION to 1/8, SEC/DIV to 100
IlS,
and VOLTS/DIV to 2 V. Probe A12U754 pin 5
for clock pulses. If not present, verify A12U754 pin 1 (RESET) is HI and A12U754 pin 11 has clock
pulses. Replace A12U754 if the signals at pins 1 and 11 are ok.
1. Make sure the Word Trigger probe connector is properly installed (connector is on the 2430 rear
panel).
Word Trigger (schematic diagram 20):
WORD
TRIGGER
If TV triggers are selected and the menu says not installed, then the diagnostics have detected a prob-
lem (if the option is installed). See Table 6-7, the Video Option troubleshooting table.
Video Option (schematic diagram 21):
VIDEO
OPTION
Table 6-6 (cont)
Maintenance-2430 Service
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