Section IV Model 6836
Paragraph 4-13
6) Rotate 683C SWEEP SELECTOR switch to RECUR. Handle the old tube as carefully as a new tube when
the old tube is to be returnedfor warranty adjustment.
7) Rotate AFREQUENCY switch to 2.1K, RF SWEEP Follow shipping instructions carefully since no allow-
RATE switch to 160K. ance will be made on a tube which is broken when it
reaches the manufacturer. In addition give complete
8) Set up counter TIME UNIT switch so that the deci- information regarding the cause of bwo tube failure,
mal point will give a 13.2-millisecond reading. if possible.
9) Set comter START TRIGGER level and STOP
TRIGGER level to about -3 volts. A. REMOVING THE BWO TUBE.
lo) The counter should read between 12.7 and 13.7 ms 1) Disconnect power from the instrument and remove
with 6836 line voltage at 115 volts. If out of specifica- the cabinet.
tions, adjust C207 (figure 4-5) for 13.2 ms sweep
time. 2) Disconnect the bwo tube multi-conductor high-
voltage cable connector (figure 4-5) from its mating
11) Rotate RF SWEEP RATE switch to 50K and read receptacle located at the left-hand side of the instru-
sweep time. The counter should read 40.0 to 43.6 ms ment, as seen from the front. Disconnect lead to
with 683C line voltage at 115 volts. If out of speci-
fications, adjust C210 (figure 4-5) for 41.8 ms. bwo control grid.
3) Remove the four screws which hold the balun
12) Rotate RF SWEEP RATE to 16K. Read sweep transformer (identified in figure 4-15) and type N
time on counter. The limits are 127 to 137 ms. connector to the front panel. Be careful to save the
Check the sweep time with RF SWEEP RATE at 5K. screws. Do not remove the coaxial cable from the
The limits are 400 to 436 ms. If either sweep time
is out of specifications, correct the setting of R225 balun transformer. Do not disassemble the balun
(figure 4-15) so that for both the 16Kand 5K positions transformer.
of RF SWEEP RATE the sweep times are within the 4) With a #lo allen wrench mounted in a driver handle
specified limits. 8 to 10 inches long, back off the two #10 allen screws
13) Repeat step 12 for sweep rates of 1.6K and 500. at the front and rear of the magnet castings. Note:
Specifications: 1.27 to 1.37 sec and 4.0 to 4.36 sec. #lo allen drivers can be ordered from the Hewlett-
Packard Company. The stock number is given in
If out of specifications, adjust R226 (figure 4-15). section V, Table of Replaceable Parts, under miscel-
laneous. (These screws bear against the tube cap-
14) Repeat step 12 for sweep rates of 160 and 50. sule.) The front screws are easily seen and are
Specifications: 12.7 to 13.7 sec and 40.0 to 43.6 sec.
If out of specifications, adjust R227 (figure 4-15). accessible from the top and right side of the instru-
ment. Back them off about 1/2 inch. The two rear
screws are not seen so easily since they are under
15) Measure sweep time with RF SWEEP RATE at the top and side deck. One screw is accessible from
16. Specifications: 127 to 137 sec. Generally no a hole near the magnet supply resistor board on the
adjustment should be required. However, if specifi- top of the instrument, and the other through a hole
cations are not met, change the valueof R232 slightly.
(R232 is a 3.3 megohm resistor on switch S203; above XV208 on the side of the instrument. The angle
see figure 4-15.) at which the wrenches make contact with the screws
is indicated in figure 4-9. Looking into the magnet
from the rear of the magnet, the screws may be seen.
16) Connect the SWEEP OUTPUT to the vertical input Back them off until they are out of contact with the
of the oscilloscope. Set the RF SWEEP RATE switch
to 160K and AFREQUENCY switch to 2.1K. Adjust capsule; this will be approximately 1/2 inch.
the oscilloscope controls to display a 20- to 25-volt
sawtooth voltage of 13- to 14-ms duration.
5) Carefully remove the capsule from the rear. Feed
the high-voltage cable and connector through the
17) Measure the sweep starting voltage which will magnet core.
appear as a vertical step at the beginning of the saw-
tooth (see figure 4-6). The step must be between
1 and 2 volts. If necessary, adjust R217 (figure 4-15) 6) Follow the Backward-Wave Oscillator Tube Claims
and Adjustment Procedure instructions in this manual.
to obtain approximately 1.5 volts. Final adjustment Pack the bwo tube, output cable and balun transformer
is made when making the rf sweep adjustments (para- with connector, as directed, to insure safe arrival
graph 4-14, step 7). at the factory.
4-13. REPLACEMENT OF BWO TUBE, AND
B. INSTALLATION OF A NEW BWO TUBE.
CALIBRATION PROCEDURE.
Always handle the bwo tube with extreme care. The 1) Carefully feed the multi-conductor high-voltage
tube is very expensive and can be damaged by im- connector through the rear of the magnet towards the .
proper handling. The tube never should be removed front panel. The #lo allen screws at the ends of the
from the capsule for any reason! Read all the re- magnet should be backed oilt 1/2 inch so as to not
moval and installation instructions before proceeding. catch on the connector.
4-10 01130-1 |
ACEC
HEWLETT-PACKARD
