Section 11
Model 686C
Paragraphs 2-1 to 2-3
SECTION II
OPERATING INSTRUCTIONS
2-1. CONTENTS. 2. Rotate CURRENT switch to MAGNET.
Section 11 contains instructions for setting up and
3. Rotate AMPL. MOD. SELECTOR switch to OFF.
operating the sweep oscillator, instructions for modu-
lating the rf output and a discussion of some applications
4. Rotate SWEEP SELECTOR switch to OFF.
of the instrument.
5. Set POWER switch to ON. The plastic graticule at
the top of the FREQUENCY dial will glow. The
2-2. INSTALLATI0 N.
cooling fan will operate. A thermal time-delay
The Model 686C Sweep Oscillator should be placed on relay delays application of high voltage to the main
a work bench or table with at least 3 inches of clear- circuits approximately 60 seconds after the instru-
ance at the rear to insure adequate air flow through ment is energized. The magnet supply circuits
the air filter. To avoid seriously restricted air flow, are partially energized when the POWER switch is
be careful not to let loose pieces of paper, etc., re- turned ON, but do not regulate until the time delay
main in the rear area, since they can be pulledagainst has operated and the filaments in the regulator
the air filter. circuits are energized.
6. Read the magnet current on monitor meter. The
The power cable should be used in a NEMA approved
current should be 0.5 to 0.65 ampere when first
standard three-prong grounding receptacle (paragraph
turned on andwill settle at 0.70 ampere after com-
1-3).
plete warmup (1 hour). DO NOT OPERATE
Complete installation instructions for rack model in- INSTRUMENT AFTER WARMUP UNLESS THE
struments are given in paragraph 1-5. MAGNET CURRENT IS BETWEEN 0.675 and 0.725
AMPERE (see paragraph 4-21).
2-3. TURN-ON PROCEDURE. 7. Rotate the CURRENT switch to CATH.
Good operating practice insists that you follow a step
8. Set RF LEVELER switch to ON.
by step procedure when turning on the Model 686C to
protect the bwo tube. This routine will systematically
9. It is important that the meter readsthe exact cath-
check out proper operation of all critical circuits to
ode current at the frequency indicated on the meter
insure normal operation. Under normal instrument
plate. The reasons are: a) Only with rated cathode
operation no damage can be done by improper setting
current at the frequency specified, will adequate
of front panel controls, since built-in overload pro-
power be produced. b) The RF LEVELER will not
tection has been provided which will cut off primary
give the desired leveling action (*l. 25 db) if the
power to the high voltage transformer if excessive
latter conditions are not met.
current flows in the helix circuit. The overload cir-
cuits are reset by momentarily turning off power to
10. Rotate CATHODE CURRENT control clockwise and
the instrument. In addition, internal screwdriver-
observe current reading. Normal output (at least 10
adjust controls preset limits on front panel controls
milliwatts) will be obtained with cathode current
to safe values. Bwo tube currents are monitored with
value and frequency stamped on panel meter.
the built-in metering circuits, which provide a posi-
(The maximum current is limited by internal
tive check that the bwo tube is being operated in a safe
adjustments. )
manner.
11. Rotate CURRENT switch to HELIX.
To place the instrument in operation, the 16 steps out-
lined in figure 2- 1 should be followed in the order given.
12. Read the helix current. The current must be less
Additional data on some of the steps are given below
than 3 ma. Excessive helix current indicates mis-
under STEPS; before performing the turn-on procedure
alignment of the bwo tube in the magnetic field.
for the first time, read this supplemental information.
(See paragraph 4-13. )
When the turn-on procedure is followed as given be- Verify proper operation of the helix voltage supply
low, the instrument will be set up for cw operation. by rotating the FREQUENCY dial from 12.4 to 8.2
Once this operation has been established, the power kmc and noting a large variation in helix current.
level can be properly set, and the oscillator adjusted
for any other mode of operation; the rf level and fre- 13. Rotate CURRENT switch to ANODE.
quency will be accurately known.
14. The anode current will read about 0.2 ma and
STEPS:
should not exceed 0.5 ma.
1. Rotate CATHODE CURRENT control full counter-
clockwise (minimum position). 15. Rotate CURRENT switch to COL.
00034- 1 2-1 |
ACEC
HEWLETT-PACKARD
