Agilent Technologies PSG Series Service Manual page 35

Troubleshooting
Troubleshooting Assembly Level Problems
assemblies may be loading down the supply. Refer to the Power Supply vs. Assembly Matrix
(Table 1-13 on page 1-18) to find out where each supply is being used. To isolate the defective assembly, power
down the signal generator and remove one of the assemblies being biased by the faulty supply.
It is important to have only a minimum number of assemblies removed at one time.
NOTE
The power supply expects to see a minimum load, otherwise the supply voltage will
increase until an overvoltage condition exists.
Turn the signal generator ON and check the faulty supply. If it is still bad, power down the signal generator
and re-install the first assembly removed. Remove the next assembly and see if the problem is alleviated.
Continue this process until the supply is functioning properly. Replace the last assembly that was removed.
Power Switch On/OFF Line
If the control line (ON/OFF) from the A3 Power Switch located in the front panel goes to a TTL low state or if
the line impedance is less than 500 ohms, the power supply will shutdown. This signal can be measured on
the A31 Motherboard at pin 79 of P241.
To troubleshoot, turn the front panel switch on. Make sure the +15 Vdc Standby voltage is good. The ON_OFF
control line should be >3.5 Vdc. The A3 Power Switch located in the front panel controls this signal.
Front Panel Green LED Not Working and Power Supply LEDs on Motherboard Not Blinking
Overvoltage or Overcurrent Conditions
The individual supplies in the signal generator are not fused but do have the capability of shutting down if an
overvolatge condition exists. When either of these conditions exist, the front panel green LED and the power
supply LEDs blink at approximately a 2 Hz rate. The power supply is attempting to revive itself but if the
overvoltage or overcurrent condition hasn't cleared, the signal generator will remain in this mode. In some
cases, the condition may be cleared by cycling the power off and on.
To troubleshoot, isolate the defective assembly by powering down the signal generator and removing one of
the assemblies being biased by the faulty supply.
NOTE It is important to have only a minimum number of assemblies removed at one time.
The power supply expects to see a minimum load, otherwise the supply voltage will
increase until an overvoltage condition exists.
Turn the signal generator ON and check whether the overvoltage or overcurrent condition still exists. If it is
still bad, power down the signal generator and re-install the first assembly removed. Remove the next
assembly and see whether the problem is alleviated. Continue this process until the supply is functioning
properly. Replace the last assembly that was removed.
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