E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
1-11
Brightness
The A2 Display brightness can be adjusted from 50 (high brightness) to 1 (low brightness) using the RPG, arrow keys,
or the numeric keypad.
Other display features located under the
Utility > Display softkey, include a screen saver and inverse video.
Display Tests
The following two screen tests are available for the LCD:
• the Black Pixel Screen Test turns the display dark
• the White Pixel Screen Test turns the display bright
Softkey Location:
Utility > Display > More (1 of 2)
To exit the test, press any front panel key.
Symptom: Dark display
1. Ensure that the front panel green power on LED is on. If not, refer to “Power Supply Troubleshooting” on
page 1- 14.
2. Press any front panel key to disable the screen saver.
3. If the display is still bad, check P12 on the A31 Motherboard for the following signals:
• If the 5.2 Vdc line is bad, refer to “Power Supply Troubleshooting” on page 1- 14.
• If either the LIGHT_EN or VDISP are bad, check them at P221−16 and P221−55 respectively on the
A31 Motherboard. If either signal is bad at P221, replace the A18 CPU.
• If all the above signals are good, check the output of the dc to ac inverter as follows:
a. Remove the front panel from the frame, and lay the front panel face down.
b. With CN2−1 open, there is typically a 160 Vrms 40 kHz signal. If not, replace the dc to ac inverter.
If the signal is there, replace the LCD.
Symptom: Bright display without characters
1. Ensure that the front–panel green power on LED is on. If not, refer to “Power Supply Troubleshooting” on
page 1- 14.
2. Try adjusting the contrast controls.
3. Check the connection of the ribbon cable at J9 of the power switch/flat panel interface board.
4. If the display is still too bright, use an oscilloscope to check P11 of the A31 Motherboard for the following signals:
Signal State
P12−15.2 Vdc
P12−3 LIGHT_EN >3 Vdc
P12−4 VDISP Brightness = 50, VDSP < 50 mV
Brightness = 1, VDSP = 3 Vdc
Signal State
P11−4 VLCD
approximately 19.5 to 21 Vdc
a
a
If >21V check the power supplies. If the power supplies are good, replace the motherboard.
P11−6 LCD_ENABLE_H >3 Vdc
P11−9, 10, 12, 13, 15, 16, 18, 19, 21, 22, 24, 25, 27, 28, 30, 31, 33,
34, 36, 37, 39, 40
Refer to Figure 1- 1.
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