Adjustment of Regulated B + Voltage

11-6625-255-14/TO

33A1-13-1701

the 200 mark on the dial is exactly in line with the

pointer rests at zero on the top scale, set the meter

mark made on the face of the mounting chassis dur-

range switch to .03 R.M.S. VOLTS. Unscrew the top

ing disassembly. Position dial shaft 018 over the

METER binding post and touch the metal part of the

four mounting holes in dial hub 09 and attach in with

binding post with the finger. The meter pointer

the four Allen-head screws.

should deflect fully clockwise and pin against the

right stop. Remove the finger and note that the meter

(14) Carefully clean the dial window and attach it

to the front of the mounting chassis with the two No.

pointer returns to zero, indicating that the vtvm cir-

6-32 screws, lockwashers, and nuts.

cuit and power supply are operating properly.

(15) Position the capacitor drive assembly inside

e. If the meter pointer does not rest at exactly zero

with the meter range switch set to 300 R.M.S. VOLTS

the panel chassis assembly and attach it to the front

panel; use the four No. 8-32 Phillips-head screws.

(d above), record the meter indication. Turn the meter

(16) Place disk spring A3 over the end of dial

zero adjust screw until the meter pointer rests at ex-

shaft 0 3 and replace the lower FREQUENCY dial

actly zero on the top meter scale. Turn the spectrum

knob. Replace the upper FREQUENCY dial knob on

analyzer off. The meter pointer should drop below the

dial shaft 0 18.

0 mark. This drop should not exceed one-half division

on the top meter scale. If the drop is greater than this,

NOTE

turn the spectrum analyzer power on and turn the

zero adjust screw to obtain the same indication

After reassembly, the calibration of the dial

recorded in d above,

must be checked as described in paragraph 7-20.

f. With the power on, remove V13, If the meter

pointer does not return to zero, the thermal emission

7-13. Adjustment of Regulated B + Voltage

from V14 (TS723A/U) is too high. Replace V14, If

replacing V14 does not bring the meter pointer to

The regulated B + voltage (+225 volts) provides a

zero, replace V14 and check C18D (C38C).

part of the stability of the spectrum analyzer;

g. If, when V13 is removed, the meter pointer drops

therefore, it is important that this voltage be set cor-

to zero, replace V13 and place a wire jumper across

rectly before further adjustments are made.

the METER binding posts. If the meter pointer drops

a. Make the following connections:

to zero, the source of the meter indication is external

(1) Connect the spectrum analyzer power cord to

rf fields. If the meter pointer does not drop to zero

the variable transformer output terminals.

when the METER binding posts are shorted, remove

(2) Connect Multimeter TS352B/U (in ac posi-

V12. If the meter pointer does not drop to zero, V13 is

tion) to measure the output of the variable trans-

defective. Replace V13. If replacing V13 does not

former.

bring the meter pointer back to zero, replace original

(3) Connect Multimeter ME26(*)/U (in dc posi-

V13 and check C27.

tion) between pin 8 of V8 and ground.

(4) Connect the variable transformer to a 115-volt

h. If the meter pointer does drop to zero when V12

is removed, replace V12 and remove V11. If the meter

ac power source.

pointer does not drop to zero, V12 is defective.

b. Adjust the variable transformer output to 115-

Volts.

Replace V12.

i. If the meter pointer does drop to zero when V11 is

c. Turn the spectrum analyzer power on and adjust

removed, replace V11. If replacing V11 does not bring

control R43 (fig. 73, 74, or 75) so that the

ME26(*)/U indicates +225 volts,

the meter pointer back to zero, return original V11

and check V10.

d. Adjust the variable transformer for an output of

105 volts; the ME-26/U should not indicate less than

7-15. Adjustment of HUM BAL Control

220 volts, Readjust the variable transformer for an

Adjust for hum balance as follows:

output of 125 volts; the ME26/U should not indicate

a. Zero set the meter as described in paragraph

more than 230 volts.

714.

7-14. Zero Setting Meter M1

b. Set the function switch to DISTORTION.

Zero set meter M1 before proceeding with the

c. Connect a l0-megohm resistor across the AF

INPUT binding posts. Cover the resistor and AF

alignment procedure given below,

INPUT binding posts with lead foil. The lead foil

a. Turn the spectrum analyzer power on.

b. Set the meter range switch to 300 R.M.S.

must be grounded and completely insulated from the

VOLTS.

resistor and binding posts.

c. Set the function switch to METER.

d. Set the frequency RANGE switch to X1.

e. Set the signal INPUT control to MIN.

d. Allow the equipment to warm up. If the meter

7-14

Change 1