Troubleshooting Unlocks; 508 A6 Frac-N Loop Unlock; 513 1 Ghz Out Of Lock; 514 Reference Oven Cold - Agilent Technologies PSG Series Service Manual

Troubleshooting

Troubleshooting Unlocks

Troubleshooting Unlocks
The phase lock loop refers to part of the frequency generating circuit used to maintain the phase relationship
between the frequency generation loop and a reference frequency. By maintaining the phase relationship the
frequency accuracy of the signal generator is guaranteed.
To maintain frequency accuracy the phase lock loop compares the phase of a signal from the reference
assembly to the phase of the frequency loop signal. If the signals are slightly out of phase, the phase
comparator circuit adjusts the frequency loop signal until the two signals are in phase. If the phase
comparator circuit cannot adjust the phase of the frequency loop signal to agree with the reference signal, the
phase comparator rails and generates an unlocked message. The unlock message is immediately displayed on
the front panel display.
There are four phase lock circuits in the frequency generation loop that can generate error messages. These
phase lock loops are located on the A6 Frac-N, A5 Sampler, and A7 Reference. There is also one other phase
lock loop on the A11 Pulse/Analog Modulation Generator that can generate an error message when the signal
generator is in phase modulation mode.

508 A6 Frac-N Loop Unlock

A 508 Frac-N unlock message indicates a failure of the A6 Frac-N.
1. Check P33-15 on the A31 Motherboard for the 10 MHz sync. approx. 2 V .
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2. If the signal is present replace the A6 Frac-N.
3. If the signal is not present, troubleshoot back to the A7 Reference.

513 1 GHz Out of Lock

A 513 1 GHz Out of Lock message indicates a failure on the A7 Reference.
1. Replace the A7 Reference.

514 Reference Oven Cold

The Reference Oven Cold Error message indicated the reference has not been connected to electrical power
for 30 minutes. This message appears when the signal generator is unplugged or the reference assembly is
removed. The message is controlled by a timer and should turn off after 30 minutes. This is not a failure
unless the message does not go off after 30 minutes. If it continues to be displayed after 30 minutes, replace
the A7 Reference.

515 10 MHz Signal Bad

A 515 10 MHz Signal Bad message indicates a problem on the A7 Reference.
A7 Reference (Standard)
1. Replace the A7 Reference.
A7 Reference (Option UNJ)
1. Check the 10 MHz signal into the A7 Reference from the 10 MHz standard.
2. The signal should be 10 MHz 1.8 V into 1 MΩ.
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