Model 683C Section I1
Paragraphs 2-1 to 2-3
SECTION II
OPERATING INSTRUCTIONS
2-1. CONTENTS. been established, the oscillator may be adjusted for
Section I1 contains instructions for setting up and frequency and for amplitude modulation (paragraphs
operating the sweep oscillator, instructions for mod- 2-4 through 2-7).
ulating the rf output, and a discussion of some appli- Until thoroughly familiar with instrument operation,
cations of the instrument. it is recommended that you refer to the supplemental
information which follows.
2-2. INSTALLATION. STEPS:
The Model 683C Sweep Oscillator should be placed on The number associated with each paragraph refers to
a work bench or table with at least 3 inches of clear- the turn-on procedure step under discussion. See
ance at the rear to insure adequate air flow through figure 2-1 for the steps not discussed below.
the filter. To avoid seriously restricted air flow,
be careful not to let loose pieces of paper, etc. re- 5. Set POWER to ON. The plastic graticule at the
main in the rear area since they can be pulled against top of the FREQUENCY dial will glow. The cooling
the air filter. fan will operate. A thermal time-delay switch
delays application of high voltage to the main cir-
The power cable should be used in a NEMA approved cuits approximately 60 seconds after the instru-
standard three-prong grounding receptacle (para-
graph 1-3). ment is energized. The magnet supply circuits
are partly energized when the POWER switch is
Complete installation instruction for rack model in- turned on, but do not regulate until the time-delay
struments are given in paragraph 1-5. switch has operated and the filaments in the regu-
lator circuits are energized.
2-3. TURN-ON PROCEDURE.
6. Read magnet current on the monitor meter. The
Good operating practice dictates that you follow ,a current should be 0.5 to 0.65 ampere when first
given step-by-step procedure when turning on the turned on and will gradually settle to 0.70 ampere
Model 683C, to protect the bwo tube. This routine after a few minutes operation. DO NOT OPER-
will systematically check out proper operation of all ATE INSTRUMENT IF AFTER WARMUP THE
critical circuits to insure normal operation. MAGNET CURRENT IS NOT BETWEEN 0.675
AND 0.725 AMPERE.
Under normal operation no damage can be done by
improper setting of front panel controls since built- 8. With RF LEVELER switch to ON the 683C will
in overload protection cuts off primary power to the have a power output variation across the band of
high-voltage transformer if excessive current flows i1.5 db or less. In the RF LEVELER OFF posi-
in the helix circuit. The overload circuits are reset tion the power variation across the band will not
by momentarily turning off power to the instrument. exceed 3 db.
In addition to the overload protection, internal screw- 9. It is important that the meter reads the exact
driver-adjust controls preset limits on front panel cathode current at the frequency indicated on the
controls to safe values. BWO tube currents aremoni- meter plate. The reasons are: a) Only with the
rated cathode current at the frequency specified
tored with built-in metering circuits, which provide will adequate power be produced. b) If the latter
a positive check that the bwo tube is being operated conditions are not met, the RF LEVELER will not
in a safe manner. give the desired leveling action (+ 1.5 db).
To place the instrument in operation, the steps outlined
in figure 2-1 should be followed in the order given. 10.Rotate CATHODE CURRENT control in a clock-
Additional data on some of the steps are given below wise direction and observe the current reading.
under STEPS; before performing the turn-on procedure Normal (at least 30 milliwatts) output will be ob-
for the first time, read this supplemental information. tained with the value of cathode current stamped
on the panel meter. (The maximum current is
Figure 2-1 shows the front panel controls as well as limited by internal adjustments.)
briefly describing the steps of the turn-on procedure.
The unnumbered controls and terminals can be oper- 12.Read helix current. The current should be less
ated in any order desired, depending on the type of than 3 ma. DO NOT OPERATE THE INSTRU-
operation selected. Characteristics of the input and MENT IF THE HELIX CURRENT EXCEEDS 3MA.
output connectors are given in figure 2-10. An overload relay prevents excessive helix cur-
rent. To reset the relay, momentarily turn
With the completion of the turn-on procedure the in- POWER off, then back to ON. Excessive helix
strument is set up for cw operation at the frequency current may indicate misalignment of the bwo tube
set on the FREQUENCY dial. Once cw operation has in the magnetic field (see section IV, Maintenance).
01130-1 2- 1 |
ACEC
