48 E8257D/67D, E8663D PSG Signal Generators Service Guide
Troubleshooting
Troubleshooting Assembly–Level Problems
Symptom: amber standby LED not working properly
With the instrument plugged in and the power turned off, the front panel
amber standby LED should be on, as well as the green +15 Standby LED on the
motherboard. This is controlled by the +15 Standby line supplied by the power
supply, which is routed via the motherboard to the front panel.
To troubleshoot, turn the instrument off and follow the signal path.
Symptom: front panel green LED not working properly
When the front panel power switch is turned on, the amber LED should go out
and the green LED should come on. Also, the fan should start rotating and the
front panel display should illuminate.
Troubleshooting:
— Verify the supply voltages at P11 of the A31 Motherboard.
— If the supply voltages are correct, replace the Power Switch/Flat Panel
Interface Board.
Symptom: fan not working
The fan is connected to the motherboard, and is audible when the instrument
is on. The fan voltage is +14V.
To troubleshoot, verify that all supplies are working; disconnect the fan from
the rear panel assembly at P6 and check the fan voltage at P6–2. If the fan
voltage is correct, replace the fan.
Symptom: Instrument does not power up; power supply LEDs not on
Checking Power Supplies
Each of the power supplies has an LED on the bottom of the motherboard (see
Figure 1-4 on page 50 and Figure 1-5 on page 51). When the power supply is
functioning, the green LED lights. Use a DVM to measure the supplies on the
motherboard, and ensure they meet the following power supply specifications.
Supply
Voltage
Acceptable
Voltage
(Vdc)
Maximum
Ripple
(mVpp)
Supply
Voltage
Acceptable
Voltage
(Vdc)
Maximum
Ripple
(mVpp)
+32 32 ± 1.0 10 +5.2VDF 5.2 ± 0.15 10
+15 15 ± 0.5 10 +3.4 VD 3.4 ± 1.0 10
+15
Standby
15 ± 0.75 20 –5.2 –5.2 ± 0.1 10
+10 10.2 ± 0.2 10 –6 –6 ± 0.12 10
+9 9 ± 0.18 10 –7 –7 ± 0.1 10
+8 8 ± 0.5 10 –15 –15 ± 0.5 10
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