Troubleshooting
Getting Started with Troubleshooting
1-14
Symptom: RPG Knob Not Functioning
Ensure that the signal generator is powered-on and the front panel green LED is on. If the green LED is not
on refer to “Power Supplies” on page 1-17 for troubleshooting. When the RPG is functioning properly DS1 on
the A18 CPU will blink when the RPG knob is rotated.
Check P13-12 for +5.2 Vdc. If the voltage is not present, refer to “Power Supplies” on page 1-17 for
troubleshooting. Press the Frequency hardkey on the front panel. Using an oscilloscope monitor P13-14 and
P13-10 while rotating the RPG knob. The display frequency value should change and both signals at P13
should pulse to a TTL high. If either signal does not pulse then replace the A1 Keyboard.
If the signals are pulsing at P13 then check the signal at P221 pins 57 and 17 of the A31 Motherboard. If the
signals are pulsing, replace the A18 CPU.
Symptom: Screen Saver Not Functioning
The screen saver delay may be set for any integer from 1 to 12 hours. The A18 CPU controls the screen saver
by pulling the LIGHT_EN line low. If the delay time has elapsed and the display hasn’t gone dark, check the
LIGHT_EN signal at P12-3. If the signal is a TTL low then replace the A4 Inverter. If the signal is a TTL
high, then check it at P221-16 of the A31 Motherboard. If the signal is high at P221, replace the A18 CPU.
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