Tektronix 1L30 Instruction Manual page 73

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Fig. 6-17. Phase-lock circuit adjustments.
lock beats (see Fig. 6-19) as the RF CENTER FREQ control
is rotated.
e. Increase the generator output signal level to 5 volts.
Check for phase lock beats. There should be no sporadic
noise beats due to circuit oscillation.
f. Disconnect the Signal Generator cable from the EXT
REF FREQ IN connector. Switch the INT 1 M Hz REF FREQ
to the INT position.
g. Adjust L804 so the oscillator starts with minimum de­
lay when the INT 1 M Hz REF FREQ switch is switched to
the INT position. (Use the tuning tool for the s / 64 hexagonal
cores.)
h. Switch the INT 1 M Hz REF FREQ to the INT position,
depress the LOCK CHECK button and check for the pres­
ence of phase-lock beats as the RF CENTER FREQ control
is rotated.
i. Check the range of the FINE RF CENTER FREQ controls
as follows:
With instruments Serial No. 439 and below.
Connect the test oscilloscope probe to pin D of the
phase-lock square-pin connector, switch the INT 1 MHz
REF- FREQ to the OFF position and check for a voltage
swing that is approximately between 4 volts and 10 volts,
as the FINE RF FREQ control is rotated through its range.
With instruments Serial No. 440 and above.
1. Depress the LOCK CHECK button and rotate the
FINE RF FREQ control through its range.
reference level variation of the display as the control
is rotated. Reference level should vary approximately
■
Fig. 6-18. Typical displays when adjusting the avalanche voltage.
Fig. 6-19. Typical display showing presence of phase-lock beats,
as the RF CENTER FREQ control is rotated. Amplitude of beat signals
may vary from 1 cm to full screen depending on DISPERSION and
RESOLUTION adjustments.
Note the DC
iyc? < ffW
(A) Circuit free running.
(B) Typical display with voltage set so avalanche transistor
circuit does not free run.
± 3 cm from the center reference when the normal dis­
play baseline is at the bottom graticule line.
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