614 Chapter11
RF Section
A10 Tracking Generator (Option 002)
3. Check that ALC_EXT, measured at A17J13 pin 10, is at a TTL low
when the TG is set to ALC INT and at a TTL high when the TG is set
to ALC EXT.
4. Check that the 600 MHz drive signal is -8 dBm ±3.5 dB. If the signal
is outside of this range, troubleshoot the A15 RF assembly.
5. Check that the 1st LO input signal is +16 dBm ±2 dB. Perform the
"1ST LO OUTPUT Amplitude" performance test, measuring the
level at the end of W43 nearest A10.
6. Check the tracking adjustment controls.Monitor A14J16 pin 13 with
a DVM. On the HP 8560E/EC, use the step keys and numeric keypad
to set the COARSE TRACK ADJ value from 0 to 255. The voltage
measured should increase from 0 V to +10V.
Monitor A14J17 pin 13 with the DVM. Use the RPG knob to set the
FINE TRACK ADJ value from 0 to 255. The voltage measured
should increase from 0 V to +10V. Monitor A14J17 pin 15 with the
DVM. The voltage at this point should change as both the FINE
TRACK ADJ and COARSE TRACK ADJ values are changed;
however the voltage change per step of the FINE TRACK ADJ will
be much less (about one-sixtieth) than the voltage change per step of
the COARSE TRACK ADJ.
7. If all of the checks above are correct, the tracking oscillator might
not be functioning. Set up the HP 8560E/EC as indicated in the
"Tracking Oscillator Range Adjustment" procedure, using a
spectrum analyzer, such as an HP 8566A/B, in place of the frequency
counter. Try to adjust A10C3 until a signal is displayed on the HP
8566A/B. If adjusting A10C3 does not start the tracking oscillator
functioning, suspect the A10 tracking generator.
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