GENERAL SUPPORT MAINTENANCE
Section I. GENERAL
7-1. Voltage and Resistance Measurements
circuit tests as follows:
It shall be assumed that general support mainte-
nance personnel are capable of making most volt-
Do not remove or replace parts before
a g e and resistance measurements without de-
r e a d i n g the instructions given in Sec-
t a i l e d step-by-step instructions. Observance of
tion III, Maintenance of Spectrum
t h e following techniques will generally prove
( 1 ) Remove top and bottom dust covers.
a. W h e n m e a s u r i n g v o l t a g e s , u s e t a p e o r
(2) Remove all tubes and dial lamps.
sleeving to insulate the entire test prod except for
the extreme tip.
b. U s e t h e s a m e o r e q u i v a l e n t m u l t i m e t e r
s u l t s are obtained, perform the isolating proce-
dures described. When the faulty part is found,
repair the trouble before applying power to the
c. When servicing the Wien bridge assembly,
be careful not to disturb the placement of parts or
d . Additional Voltage Checks. W h e n m a k i n g
to bend the tuning capacitor plates; a short circuit
repairs in the spectrum analyzer always check, in
or change of alignment may occur.
a d d i t i o n to the resistance measurements, the
d. Make resistance measurements only as di-
power supply output voltages before putting the
rected on the voltage and resistance diagram (fig.
equipment back into service. Refer to table 7-2 for
e . The color code diagram for resistors and
c a p a c i t o r s (fig. FO-1) provides pertinent resist-
W h e n the spectrum analyzer is being
a n c e , voltage rating, and tolerance information.
operated from a 115V ac power source,
7-2. Checking Filament and B+ Circuits
t h e regulated +225 volts dc obtained at
pin 8 of V8 must be between 220 and 230
a. When to Check. When either of the following
volts dc for a variation in line voltage of
conditions is in evidence, check for short circuits
1 0 5 to 125 volts ac. If the spectrum
and clear the trouble before applying power.
analyzer is being operated from a 230V
( 1 ) When abnormal symptoms are present
a c power source, t h e regulated +225
whose origins are unknown.
volts dc obtained at pin 8 of V8 must be
( 2 ) When abnormal symptoms discovered
between 220 and 230 volts dc for a line
d u r i n g operational tests indicate possible power
variation of 204 to 256 volts ac.
b. Conditions for Tests. Prepare for the short
Table 7-1. Checking Filament and B+ Circuits for Shorts
Point of measurement
A lower reading maybe due to a short in
capacitor C 17 or C lg.
An infinite reading may be due to open
resistor R49, R50, R51, or R56, or
open choke L1.
If resistance is zero or infinite, check
C17, C37, R84, RS5, and L1.
If resistance is not within 10 percent,
Junction of R68 and C18D (A model),
check C18D (C38C) and R67.
R68, and C38C (B, C, and D models)
theses indicates that the latter is used in
a l l models other than the TS-723A/U.
f o l l o w e d by another symbol in paren-