HP 654A - Balance Box; Distortion Check 5-1

Model 654A
Section V
TEST OSCILLATOR
hp654A
EQUAL
CABLE
LENGTHS
BALANCE
BOX
SEE FIGURE 5-9
AC VOLTMETER
hp 400E
_J
Figure 5-8.
(Paragraphs 5-30 through 5-34) are not met, perform the
Balance Adjustments ( Paragraph 5-62 through 5-64).
5-30. 135 BAL CHECK.
a. Connect the equipment, as shown in Figure 5-8,
using the 135 ohm Balance Box: ( the parts
required to build the Balance Box are shown in
Figure 5-9) the cables from the 654A should be as
short as possible and of equal length ( jumper
cables, - hp- 10502-6001, which are made from 8
in. lengths of coaxial cable, are suitable for this
application).
b. Set the 654A controls as follows:
FREQUENCY dial 1
FREQUENCY RANGE X10
OUTPUT LEVEL dBm + 10,0
IMPEDANCE 135 BAL
AMPLITUDE Adjust for OdBm
on 654A meter.
c. Sweep the 654A slowly over the frequency range
of 10Hz to 1MHz; the ac voltmeter indication
should remain below 3.68mV rms, verifying
balance of greater than 50dB from 10Hz to 1MHz.
d. Sweep the 654A slowly over the frequency range
of 1MHz to 5MHz; the ac voltmeter indication
should remain below 11.6mV rms, verifying
balance of greater than 40dB from 1MHz to
5MHz.
5-31. 150 BAL CHECK.
5-32. Repeat the procedure of Paragraph 5-30 with the
following changes:
in step a. use the 150 ohm Balance Box ( See
Figure 5-9);
in step b. set IMPEDANCE to 150 BAL;
in step c. ac voltmeter indication should be below
3.87mV rms;
Balance Checks
in step d. ac voltmeter indication should be below
12.25mV rms.
5-33. 600 BAL CHECK.
5-34. Repeat the procedure of Paragraph 5-30 with the
following changes:
in step a. Use the 600 ohm Balance Box ( See
Figure 5-9);
in step b. Set IMPEDANCE to 600 BAL;
in step c. ac voltmeter indication should be below
7.75mV rms;
in step d. ac voltmeter indication should be below
24.5mV rms.
5-35. DISTORTION CHECK.
a. Connect a distortion analyzer to the 654A 50 ohm
output as shown in Figure 5-10.
BALANCE BOX
RI
300
654A-9 . 891
Parts List: ( All resistors 1/8 watt metal film.)
RI, R2
R3
Rp:
300 ohms +/-. I%
150 ohms +/- 1%
-hp- 0698-6295
-hp- 0757-0284
Input Impedance
Rp, +/- 1%
135 ohms
150 ohms
600 ohms
174 ohms, - hp- 0698-4417
200 ohms, - hp- 0757-0407
open
Figure 5-9. Balance Box
5-9