Agilent Technologies 856290216 Manual Probe Troubleshooting, LO Control Check, RF Low Band Check

LO Control Check

The LO control check verifies that all phase-lock loops (PLLs) in the synthesizer section lock. Some oscillators are checked to ensure that they will lock outside their normal operating frequency range. The TAM also performs an operational check on several DACs in the synthesizer section.

RF Low Band Check

The TAM tests the operation of the A8 low band mixer, the A9 input attenuator, the A10 YIG-tuned filter/mixer (RYTHM), the second IF distribution, the third converter (A15), and most of the Al3 second converter.

AFI also checks the flatness compensation amplifiers (part of the Al5 RF assembly), ensuring that their gain can be adjusted over a certain range.

If no signal is detected through the RF section, AFI will substitute the 298 MHz SIG ID oscillator, if present, for the third LO while simultaneously decreasing the first LO frequency by 2 MHz. If a signal can now be detected, troubleshoot the third LO driver amplifier on the Al5 RF assembly.

Manual Probe Troubleshooting

Manual probe troubleshooting probes the instrument test connectors to perform the following types of measurements:

nAmplifier and oscillator dc current draw by monitoring the voltage across a resistor of known value.

w Oscillator tune voltages ensuring proper operation of phase/frequency detectors and loop integrators.

w Static bias voltages.

w DAC output voltages.

If probing a connector for a check yields a “FAIL” indication, select the desired check using either the knob or step keys and press Maze Info. A description of the function checked (with measured and expected voltages or currents) is displayed with a list of additional areas to check. These areas can sometimes be checked by looking at another TAM connector, but usually require manual troubleshooting techniques to isolate the problem further. If an HP-IB printer is connected, press Print Page to provide a hard copy of the currently displayed screen (the softkey labels will not be printed).

Each test connector has fifteen pins (one pin is missing to act as a key). The pins contain eight measured signal lines (measured signal lines denoted as MS1 through MS8), one input signal line (OSl), one ground, and five pins encoding a five-bit connector address.

The TAM needs to probe each assembly revision connector once; subsequent readings are not necessary. It is possible, for example, to probe the A5 IF assembly, then the A4 log amplifier assembly, and then return to A5 without having to re-probe A5 revision connector. However, the revision connector must be re-probed if the spectrum analyzer is returned to normal operation and then back to TAM control. (This is also true if the spectrum analyzer is turned off.)

General Troubleshooting 7-l 5