Tektronix 1L40, Инструкция по эксплуатации

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Maintenance— Type 1L40
Oscillator Tube Replacement
NOTE
A com plete o sc illa to r assembly and its sub parts are
listed in the M echanical Parts section. W e recom ­
mend re p la cin g the com plete assembly and re tu rn ­
ing the defective assembly to your T ektronix Field
o ffic e or representative.
Replacing com ponents,
such as the o sc illa to r tube, requires re c a lib ra tio n
o f the o s c illa to r. This requires special test e q u ip ­
ment and techniques. A c a lib ra tio n procedure is
pro vid e d fo llo w in g tube replacem ent instructions,
how ever, this procedure is pro vid e d fo r use o n ly
if it is im p ra ctica l to return the o s c illa to r assembly
to T ektronix.
The procedure to replace the oscillator tube V42 is de­
scribed and illustrated in Fig. 4-4A and B.
Oscillator Calibration
CAUTION
The c a lib ra tio n o f this o s c illa to r is very critica l
and should o n ly be a ttem pted by q u a lifie d person­
nel w ith a d e q u a te fa cilitie s.
Refer to Fig. 4-3 for the location of the sub-assemblies
and ports. The oscillator assembly must be removed for
calibration. The probe assemblies can be oriented within
the magnetic field of the oscillator chamber by loosening
set screws and positioning the probe in or out of the chamber
or rotating the probe within the field.
Usually the probes are rotated for maximum power output
and inserted in or out of the chamber for the specified power
output. It is important to keep the output power below the
maximum specifications listed in steps 1 (m) and 1 (o) of the
following procedure. All adjustments interact; therefore, as
each adjustment is made, its effect on the frequency tracking
and output power over the frequency range of the oscillator
must be checked. Adjust to obtain as fla t an output as pos­
sible with frequency tracking within ± 1 %.
Alignment Procedure for Oscillator Assembly,
Tektronix Part No. 1 1 9 -0 1 0 8 -0 0
This procedure should be used only after replacing the
oscillator tube. Refer to Fig. 4-3 for the location of sub
assemblies and ports. The oscillator assembly must be re­
moved for calibration.
1. Alignment and Installation of the Probes and Varactor
Assemblies.
a. Install probe assembly (Part No. 119-0107-01 into the
No. 2 port (Fig. 4-3). Position the probe assembly approxi­
mately '/ , 4 inch out from full penetration with the notch or
keyway (DC return of the probe) towards the plate end of
the oscillator assembly, and secure by tightening one of
the two set screws.
CAUTION
Do n o t o ve r-tig h te n set screws. They may w a rp
the sh a ft if tig h te n e d to o much.
b. Install probe assembly (Part No. 119-0107-00) into
the No. 1 port (Fig. 4-3). Position the probe assembly
approximately '/u inch out from full penetration with the
notch or keyway towards the plate end of the oscillator
assembly, and secure by tightening one of the two set
screws.
c. Install the Varactor assembly (Part No. 119-0105-00)
into the control port. Position the assembly approximately
'/ i 4 inch out from full penetration and secure by tightening
one of the two set screws.
d. Position the cathode and plate chokes to the high
frequency end of the band (towards the center of the
assembly) but not against the stop.
e. Connect an RF power meter through a 50 Q, 10 dB
attenuator and a 9 inch coaxial cable (clear cable covering)
to the No. 2 port.
f. Connect a frequency counter or accurate frequency
measuring device through a 50
Q
termination and a 9 inch
lossy coaxial cable (white cable covering) to the No. 1
port.
g. A pply power (B + and filament supply) to the oscil­
lator. A llow approximately 10 minutes for the oscillator
to stabilize.
h. Loosen the set screw to No. 2 port and rotate the
probe assembly for maximum power input. Do not rotate
the probe 180° from the preset position. If power output
exceeds 100 mW, decrease the coupling by pulling the
probe assembly out. Tighten the set screws.
i. Loosen the set screws (1) in Fig. 4-3, and position the
plate choke for a frequency of 4.2 GHz.
Force the lead screw against the bearing and tighten
the set screws.
j. Loosen the set screws (2) in Fig. 4-3, and position the
cathode choke for maximum power output. Decrease probe
coupling if power output exceeds lOOmW.
Force the lead screws against the bearing and tighten
the set screws.
k. Connect the Varactor terminal to a + 1 .5 V to + 1 4 V
bias supply. The instrument bias supply is preferred. Set
the Varactor bias voltage to + 7 V and tune the oscillator
to its mid-frequency position.
l
. Vary the position of the Varactor assembly, until a
bias swing from + 1 .5 V to + 1 4 V, provides a frequency
shift equal to or greater than 1.5 MHz. Return the bias
voltage to + 7 V , by adjusting the RF CENTER FREQ,
control.
m. Tune the oscillator through its frequency range check­
ing the output power. Power output over the range should
not exceed lOOmW or decrease below 5 mW.
n. Remove the RF power meter from the No. 2 port
and connect the meter through a 50 fl, 10 dB attenuator
and 9 inch lossy cable to the No. 1 port. Connect the 9
inch (not lossy) coaxial cable from the instrument phase
lock circuit to the No. 2 port.
o. Tune the oscillator through its frequency range
checking the output power from the No. 1 port. Power
output should not exceed 16 mW or decrease below 2 mW.
4 -4
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