Hammarlund SP-600-JX User manual

4 SEPTEMBER 1952
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AN 16-45-223
HANDBOOK
OVERHAUL INSTRUCTIONS
RADIO RECEIVER
MODEL SP-600-JX
(HAMMARlUND)
PUBLISHED UNDER AUTHORITY OF THE SECRETARY OF THE AIR FORCE
AND THE CHIEF OF THE BUREAU OF AERONAUTICS
L- ~ __ -~--*---------------
D'Arcy Ptg. & Litho Corp., New York, N. Y., 3100-11/5/52

AN 16-45·223
Reproduction for non-military use of the information or illustrations contained in this publi-
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AN 16-45-223
TABLE OF CONTENTS
Section
Page Section
Page
I DESCRIPTION AND LEADING PARTICULARS
1- 1. General. . . . . . . 1
1- 3. Pertinent Information. . . . . . 1
III SPECIALIZED MAINTENANCE AND REPAIR
3- 1. General. . . . . . . . . . .. 3
3- 5. Specialized Maintenance of Parts 3
II
SPECIAL OVERHAUL TOOLS AND TEST
EQUIPMENT
2- 1. Special Tools . . . . . . . . . 2
2- 3. Special Test Equipment. . . . . 2
IV DISMANTLING AND DISASSEMBLY
4- 1. Preliminary Procedure. . . 4
4-
2. Dismantling of Tuning Unit Assembly 4
4- 4. Disassembly of Gear Train Assembly 6
4- 5. Chassis Disassembly. . . . . .. 6
13
13
13
13
VII
REPAIR AND REPLACEMENT
7- 1. General .
7- 2. Switch Base and Spring Assembly
7- 3. Selectivity Switch
7- 4. Retropicalization ... . . . .
VIII REASSEMBLY
AND TESTING OF SUB-
ASSEMBLIES
AND ASSEMBLIES
8- 1. Reassembly .14
8- 2.
Reassembly of Tuning Unit Assembly
14
8- 3.
Resoldering and Retropicalization
15
8- 4. Testing of Subassemblies and
Assemblies
15
IX
REASSEMBLY AND TESTING OF
COMPONENTS
9- 1.
Reassembly .15
9- 2.
Reassembly of the Chassis and
Tuning Unit Assembly 15
9- 3. Reassembly of the Chassis and
Panel Assembly
16
9- 4.
Reassembly of the Radio Receiver
16
9- 5. Reassembly of the RF Tuners
16
9- 6. Testing.
17
XFINAL ASSEMBLY
10-1. General.
17
XI INSPECTION
AND TESTING
11-1. General.
17
11-2.
Minimum Performance and Test
Values
17
INDEX 18
7
7
7
7
VCLEANING
5- 1. Overall .....
5- 3. Electrical Parts.
5- 5. Mechanical Parts
5- 8. Preservation After Cleaning.
VI INSPECTION
6- 1. General. . . . . . . . 8
6- 3. Inspection Technique . . 8
6- 4. Receiver Abnormalities. 8
6- 5. Receiver Inspection 8
6- 8. Subassembly Inspection. 8
6-10. Parts Inspection .... 8
6-29. Functional Mechanical Parts 12
6-30. Mechanical Performance Standards 12
6-31. Life of the Receiver 12
6-32. Service Limits. • . . . . . . .. 12
LIST
OF ILLUSTRATIONS
Figure
Page Figure
Page
1-1.
Radio Receiver, Model SP-600-JX.
2-3. Special Tools to Reassemble Turret
Rack Mountings .
ii Rotor Assembly.
"2
2-1.
Special Tools to Reassemble RF
2-4.
Special Tools to Reassemble Gear
Strip Assembly ......... 2
Train Assembly.
\2
2-2.
Special Tools to Reassemble Tuning
4-1. Gear Train Assembly, Exploded View .5
Unit
Shield Assembly
2
LIST
OF TABLES
Table
Page
2-1.
9-1.
Special Tools Required for Overhaul
Identification of the r-f Tuners . . . 1
16

AN 16-45-223
Figure 1-1. Radio Receiver, Model SP-600-JX Rack Mountings
ii

AN 16-45-223
SECTION I
DESCRIPTION AND LEADING PARTICULARS
Section I
Paragraphs 1-1 to 1-4
1-1. GENERAL.
1-3. PERTINENT INFORMATION.
1-2. This publication comprises overhaul instruc-
tions for the Radio Receiver, ModeI SP-600-JX rack
mounting (See figure 1-1.), manufactured by the
Hammarlund Mfg. Co. New York 1, N. Y. The re-
ceiver, designed for direct mounting in a standard
19-inch relay rack, is a 20-tube general purpose
radio communication receiver with a self-contained
stabilized power supply suited to operate from a
single phase 50- to 60- cps, 90 to 270 volt a-c source.
It provides for the continuously variable or crystal
controlled fixed frequency reception of any radio fre-
quency carrier in the 0.54 to 54.0 me frequency
range. The rotary turret which houses the six fre-
quency bands of the receiver, in association with the
gear-train drive, provide for the excellent mechani-
cal stability for which the receiver is known. Also,
its precise mechanical construction enables full ad-
vantage to be derived from the crystal filter incor-
porated in the i-f amplifier of the receiver. The re-
ceiver functional circuitry is mostly contained in sub-
assemblies, all of which may be subjected to indivi-
dual replacement whenever the need arises for re-
ceiver repair. The receiver is designed for fixed
and/or mobile operational activities such as are en-
countered at enclosed base or field stations, on ship-
board, or when airborne. Such activities may be
subject to wide ranges in temperature and humidity
since the receiver is adequately conditioned for tropi-
cal use. The receiver is fully shielded to keep its
radiation characteristics to a possible minimum.
1-4. The radio receiver is suited to operate in single
or multi-receiver two-way operational activities. Any
activity requires that certain auxiliary components be
associated with the receiver. Apart from the phone
jack contained in the front panel of the receiver, all
the receiver inter-connecting means are located on
the rear apron. The rear apron also contains two
fuse holders, one for a three ampere cartridge type
fuse in series with the power transformer primary
winding, and the other for a duplicate spare. The
power transformer secondary plate winding is fused
by a three-eighths ampere pigtail type fuse soldered
between the transformer terminal 11 and chassis
ground. The front panel of the receiver contains all
the receiver operating controls. All the receiver ad-
justment controls are located on the rear apron. The
coil adjustable tuning cores and trimmer capacitors
used to align the receiver, and the adjustment con-
trols on the rear apron, maintain their alignment and
adjustment settings for long periods of time. Through
the use of various types of springs, all the receiver
adjustable fixed and moving parts are provided with
positive positioning and operation. Also, flat springs
are used on the rotary turret assembly to provide for
electrical grounding. The receiver r-f coils, r-f
chokes, and all soldered connections are fungicidal
varnished for tropicalization; also, all metal parts in
contact conform to the electrochemical series of ele-
ments so that corrosion is kept to a possible mini-
mum. In view of the fact that all possible precau-
Table 2-1. Special Tools Required for Overhaul
Figure &
Hammarlund Tool
Index No.
Tool No. Name
Application
2-1,1 T7982-5
Pin, locating
2-1,2 T7982-6
Bar,
line-up
RF strip assy.
2-1,3 T7982-7
Pin, locating
2-2,1 T8331-1
Swage
Contact spring and partitions,
tuning
2-2,2 T8331-2
Mounting, seat
unit shield.
2-3,1
T7644
Jig, fixture
Turret rotor assy.
2-3,2 T8332 Rod
Turret rotor and tuning unit shield,
line-up.
2-3,3
T8333
Wrench,
spanner
Turret rotor assy nuts.
2-4,1 T8335
Jig
Band dial location.
2-4,2 T8334
Pliers
"C" washers, crimping.
1

Sections I-II
AN 16-45-223
tions are taken at the factory to provide each receiver
for use in perfect condition, the preventive mainten-
ance and overhaul performed on the receiver should
be done with the least possible recourse to the need-
less unsoldering and replacement of parts.
SECTION II
SPECIAL OVERHAUL TOOLS AND TEST EQUIPMENT
L
2-1. SPECIAL TOOLS.
2-2. The special overhaul tools required to perform
the work outlined in this publication are listed in table
2-1. The table refers to the figure and index number
of the illustration for each tool, the tool number, and
the tool name. The application column in the table
briefly denotes the receiver subassembly or parts to
which the respective tools are applied when the re-
1. Large pin 2. Line-up bar
3. Small pin
Figure 2-1. Special Tools to Reassemble
RF Strip Assembly
2
ceiver is overhauled. The manner of use and applica-
tion of each tool is outlined in detail in paragraphs
7-2, 7-3, 8-2.
2-3. SPECIAL TEST EQUIPMENT.
2-4. No special test eqUipment is required to align,
adjust, or final test the radio receiver. To facilitate
the testing of the receiver a test position should be
maintained, provided with the appropriate test equip-
ment and fabricated cables, as described in the ap-
plicable handbook of service instructions.
~===~
1. Fixture jig 2. Rod
3. Spanner wrench
Figure 2-3. Special Tools to Reassemble
Turret Rotor Assembly
1. Swage 2.
Seat mounting
1. Jig 2. Pliers
Figure 2-2. Special Tools to Reassemble
Tuning Unit Shield Assembly
2
Figure 2-4. Special Tools to Reassemble
Gear Train Assembly

AN 16-45-223
SECTION III
SPECIALIZED MAINTENANCE AND REPAIR
Section III
Paragraphs 3-1 to 3-10
3-1. GENERAL.
3-2. The specialized maintenance and repair activi-
ties within the scope of depot overhaul are based on
receiver trouble-shooting data supplementary to that
provided in the applicable handbook of service instruc-
tions. The data is useful in the step-by-step proce-
dures used to determine specific circuit failures.
3-3. Before specialized maintenance and repair acti-
vities are resorted to, ascertain whether the receiver
fault is due to anyone or more of the following causes:
a. Damage or miswiring.
b. Abnormal short circuits between parts or to
ground, prior to or subsequent to the reassembly of
the subassembly or part to the receiver.
c. Faulty parts, whose fault is only evident when
the part has been allowed to warm up by turning the
receiver "on".
3-4. All of the receiver circuitry is accessible, a-
part from that contained in the r-f strip. When the
receiver fault is isolated to the r-f strip, it must in
any
case be removed from the receiver for repairs or
for replacement. To determine the specific cause of
the r-f strip failure requires part by part analysis to
the extent required to isolate the faulty part. The r-f
strip removed for repairs may be externally recon-
nected to the receiver through means of insulated
"pee-wee" clip leads, to render accessible its cir-
cuitry for purposes of analysis. When doing this do
not
attempt to reconnect the four gang variable tun-
ing condenser unless it too or a spare is external to
the receiver. The r-f tuners for the frequency band
desired may be seated in the r-f strip steatite base
"V" contacts for same.
WARNING
Keep
the receiver turned "off" when extern-
ally reconnecting the r-f strip to the receiver.
3-5. SPECIALIZED MAINTENANCE OF PARTS.
3-6. The specialized maintenance of parts outlined
in each of the follOWing categories differs from that
outlined in the applicable handbook of service instruc-
tions to the extent that the parts are all analysed with
regard to possible failure while contained in the re-
ceiver which remains turned "on" and allowed a
warm-up period of at least five minutes.
3 -7 .RESISTOR FAILURE. To determine whether a
resistor is ·fiormal as evidenced by its resistance
value in ohms, determine first its circuit function,
noting whether it is isolated or whether it has a d-c
voltage drop across it. If the former, determine
first, utilizing a volt-ohmmeter, that it has no d-c
voltage across it, possibly due to the failure of its as-
sociated isolating capacitor, and then measure its
resistance utilizing the volt-ohmmeter. If the latter
turn the receiver "off" to measure the resistance of
the resistor. To measure the resistance of resistors
R32, R33, R60, R61, R66,R68, R93,R94, R95,R96,
and R97 unsolder one resistor lead to isolate the re-
sistor from the resistor network of which it is part.
3-8. CAPACITOR FAILURE. To determine whether
a capacitor is abnormal to the extent that it is open,
shorted, or leaky, i. e. , its construction is at fault in
the latter instance such that it has internal series re-
sistance or a conductive shunt path other than normal,
determine first its circuit function, noting whether it
is used for d-c voltage isolating or filtering purposes,
for tuning purposes, or to provide alow impedance
series or shunt path for the signal itself.
3-9. OPEN CAPACITOR. An open capacitor cannot
provide alow impedance series or shunt path for the
signal or be used to tune a circuit to resonance. Al-
so, it cannot provide for filtering action, but will
keep a circuit isolated. In the isolating instance the
capacitor usually carries the signal or other a-c
voltages across it so that an open capacitor can al-
ways be analysed with regard to its circuit function.
To do this apply an appropriate signal to the appli-
cable test point such that the capacitor under con-
sideration, if normal, may perform its function, and
utilize an a-c vacuum tube voltmeter or acathode ray
oscilloscope indication to determine whether the capa-
citor is open. Each of the following circuit indica-
tions, as applicable, provide for checking an open ca-
pacitor.
a. When the capacitor is in series with the signal
path of the receiver, but open, its input signal indi-
cation is much higher than its output signal indica-
tion, to ground in each instance.
b. When the capacitor provides a return path to
ground for the signal, but is open, its away-from-
ground terminal is at an a-c voltage level above
ground.
c. When the capacitor is used to tune a circuit to re-
sonance, but is open, the circuit inductance cannot be
adjusted for resonance.
d. When the capacitor is used to prOVide audio filter-
ing action, but is open, its away-from-ground ter-
minal will provide indication of excessive ripple, as
compared to when the open capacitor is shunted by a
normal capacitor.
e. When the capacitor is used to provide decoupling
action in r-f circuits, but is open, more signal indi-
cation may be observed, as compared to when the
open decoupling capacitor is shunted by a normal ca-
pacitor.
3-10. SHORTED CAPACITOR. The effect a shorted
capacitor has on the receiver cirCUitry is such that
the shorted capacitor may be rapidly identified. This
3

Sections III -IV
AN 16-45-223
is due to the fact that the shorted capacitor cannot
have a d-c or a-c voltage drop between its terminals.
Each of the following circuit indications, as appli-
cable, provide for checking a shorted capacitor.
a. When the capacitor circuit connection is such that
one of its terminals is normally at some d-c voltage
above ground, it cannot provide a d-c voltage indica-
tion to ground when a volt-ohmmeter or d-c vacuum
tube voltmeter is used to make the test.
b. When the capacitor circuit connection is such
that only an a-c voltage is normally effective at its
terminals, possibly due to the signal, and the capa-
citor is shorted, no vacuum tube voltmeter or oscil-
lograph indication across the capacitor results. In
this instance the signal usually is not evident in the
receiver circuitry immediately following the capaci-
tor.
c. When the capacitor is used as a trimmer capaci-
tor, and is shorted, it has no trimmer effect on tuned
circuits. In this instance and when the capacitor is
used to provide for the parallel resonance of adjust-
able core tuned circuits, the signal is usually no long-
er evident in the subsequent receiver cirCUitry.
d. When
the capacitor is shunted by a resistor as is
the case in certain of the r-f tuners, and it is sus-
pected that the capacitor is shorted, the shunted re-
sis tor , measured for resistance (Refer to paragraph
3-7.), will determine whether the capacitor is short-
ed. If an indication across the capacitor is to deter-
mine whether it is shorted or not, be sure to provide
enough signal input to the receiver.
3-11 LEAKY CAPACITOR. In the rare instance
when a capacitor is suspected of being leaky such that
its leakage characteristics are to be determined, a-
void haVing to unsolder one of the capacitor terminals
from the receiver by utiliZing every possible receiver
switch and/or tube means to provide for isolating the
capacitor terminal. To determine whether a capaci-
tor is leaky do the following:
a. Turn the receiver to its a-c power "off" position.
b. Adjust the volt-ohmmeter to its highest ohmmeter
range and connect it across the capacitor. If the ca-
pacitor is good the ohmmeter needle flicks over
slightly and gradually drops back to infinity.
c. Now reverse the test prods and note that the
·ohmmeter needle flicks to twice the deflection it did
before, the needle then returning to the position in-
dicating infinite resistance, if the capacitor is good.
If the needle does not go back to infinite resistance
indication the capacitor is leaky and should be replac-
ed. This test is not reliable for capacitors whose
capacitance value is less than 0.05 ufo
NOTE
When
the capacitor is an electrolytic capacitor
one reading will show low resistance and the
other much higher. If the higher resistance is
not over 100,000 ohms and comparable to that
of a prototype capacitor, the electrolytic ca-
pacitor must be replaced.
Make sure to turn the receiver "on" at least
15 minutes before making the test to render
assurance that the electrolytic capacitor di-
e lectric film deterioration due to shelf life, if
any, may be repaired due to subjecting the
capacitor to its d-c working voltage.
SECTION IV
DISMANTLING AND DISASSEMBLY
4-1. PRELIMINARY PROCEDURE.
a. Remove the cartoned radio receiver from its
wooden shipping box and then unpack it completely.
b. Dismantle the radio receiver top cover and bot-
tom plate, from the receiver chassis and panel as-
sembly.
c. Dismantle the electron tube complement, the front
panel controls, the frequency control unit switch arm
and eccentric drive assembly, the front panel assem-
bly, etc., from the receiver chassis and panel as-
sembly.
d. Strip the receiver chassis and tuning unit assem-
bly with regard to main dial indicator and mounting,
both main and vernier dials, both side plates, etc.
4-2. DISMANTLING OF TUNING UNIT ASSEMBLY.
To
dismantle the tuning unit assembly from the re-
ceiver chassis and tuning unit assembly, use the fol-
lowing step procedure:
a. Unsolder two green/white leads, one each from
the E14 and E17 terminal strips.
b. Unsolder two blue/black leads from the T2 second
4
mixer transformer.
c. UIisolder white/black, red/white, blue/red, yel-
low/black, and red/green leads from the E13 ter-
minal strip.
d. Unsolder two red/green, one green/red, and one
yellow/red leads of the main wiring cable from the
S4 conversion switch.
e. Remove two No. 10-32 screws and one stud post
assembly, on either side of tuning unit assembly,
which screw into nut plate brackets through clearance
holes in gear-train plate and chassis proper.
f. Remove one No. 10-32 screw in angle bracket on
rear of tuning unit assembly which passes through
clearance hole at back of chassis proper.
g. Lift out the tuning unit assembly.
4-3. The tuning unit assembly comprises several
subassemblies which may be dismantled from it and
then separately disassembled. These are the follow-
ing:
a. The mixer plate coil assembly, T1.
b. The r-f wiring assembly, i. e. , the r-f strip.

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Figure 4-1. Gear Train Assembly, Exploded View
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Section IV
Paragraphs 4-4 to 4-8
AN 16-45-223
c. The variable capacitor, i. e. , the eight section,
four-gang tuning capacitor.
d. The gear-train assembly.
e. The 24 r-f coil assemblies, i. e., the r-f tuners.
4-4. DISASSEMBLY OF GEAR TRAIN ASSEMBLY.
The gear-train assembly (See figure 4-1. ), is disas-
sembled in accordance with the following step-by-
step procedure.
a. Remove cam, hub, and band change dial assem-
bly(l).
b. Remove indicator slide helical spring (2) and con-
version switch helical spring (3).
c. Remove conversion switch lever assembly (4).
d.
Remove the two band change helical springs (5),
and
then remove the band change cam detent roller
and lever assembly (6).
e. Remove the three No. 10-32 screws (8) used to
mount the three mounting posts (7), to which are at-
tached the bearing plate (9) and the bearing plate (10),
Doing
this provides for the dismantling of the movable
support main pointer bracket (15), the shaft, gear,
and hub assembly (16), the cam (25) which activates
roller and arm assembly, the ball bearings (20), the
flywheel (22), the idler wheel (23), and the gear and
drive pin assembly (21).
f. Remove the two spur type gear assembly (26)
from the spider assembly at the top right side of the
base plate assembly (43), and then remove the spur
type gear (27), with included stop pin.
g. Remove spur type gear (28) from top left side of
the base plate assembly (43) and the main dial hub
spur type gear (29) adjacent to it.
h. Remove gear assembly (31), which includes two
spur gears mounted on a small brass plate.
i. Remove the spur type gear (38) and the spur type
gear (37).
j. Remove the rotor assembly front bearing hub(36)
and the machine screw (42) at the rear from the rotor
assembly, and lift outthe mounting disc and shaft as-
sembly (35).
k.
Disconnect the base plate (43) from the tuning
unit shield assembly (45).
4-5. CHASSIS DISASSEMBLY. The chassis assembly
may be disassembled in any sequence desired subse-
quent to the removal of the three section, four pole,
20-position rotary selectivity switch assembly which
is removed first to get at all chassis wiring under-
neath it. This switch assembly comprises the S5A,
6
B, C rotary switch, three resistors, five insulated
electrical wires, eight bare electrical wires, and two
pieces of vinylite tubing which cover in part two of the
bare electrical wires. The switch assembly is re-
moved in preference to removing the rotary switch
proper to facilitate the unsoldering necessary during
removal.
4-6. Certain other subassemblies and parts of the
chassis assembly, likewise, are unsoldered in a man-
ner to facilitate the unsoldering necessary during re-
moval. These are:
a. The bfo injection potentiometer which is removed
with all the electrical wire leads that are soldered to
it.
b. The audio output transformer which is removed
with all the electrical wire leads and one capacitor
that are soldered to it.
c. The antenna input socket which is removed with
two
black electrical wires that are soldered to it.
d. Both the large octal sockets which are removed
with the electrical wire leads, resistors, and capa-
citors that are soldered to them.
e. The meter a-f adjustment potentiometer is re-
moved with the electrical wire jumper and resistor
that are soldered to it.
4-7. The r-f strip, i. e., the r-f wIrmg assembly,
which is contained in the tuning unit assembly, has
its tube sockets removed with the bare electrical
wires that are soldered to certain of the tube sockets.
Also, the isolantite switch bases of the r-f strip are
removed with the bare electrical wires, certain re-
sistors, and certain capacitors soldered to them,
which do not interfere with the removal.
4-8. The frequency control unit and the audio filter
assembly, which are contained in the chassis and pan-
el assembly of the receiver, may be dismantled from
the receiver at any stage in the overall disassembly
procedure outlined. The frequency control unit octal
socket and selector switch are disassembled by un-
soldering the bare electrical wire leads soldered to
them away from the socket and switch contact ter-
minals; also, having disassembled the octal socket,
the bare electrical wire common to the six crystal
sockets is unsoldered subsequent to the removal of
the crystal socket plate carrying the crystal sockets.
The audio filter assembly is disassembled subsequent
to its dismantling as a unit.

AN 16-45-223
SECTION V
CLEANING
Section V
Paragraphs 5-1 to 5-12
5-1. OVERALL.
5-8. PRESERVATION AFTER CLEANING.
5-2. The radio receiver may be blown out with com-
pressed dry filtered air at a pressure of approxi-
mately 100 lb/sq in. Accessible parts may be wiped
with a clean cloth. Not too readily accessible parts
may be dusted with a small dry brush.
5-3. ELECTRICAL PARTS.
5-4. When the radio receiver is dismantled and its
subassemblies are disassembled all wired electrical
parts may be blown out, wiped, and dusted as outlined
above (Refer to paragraph 5-2.), for the overall re-
ceiver. The air pressure at the subassembly or part
may be decreased by increasing the distance between
the air nozzle and the work.
WARNING
Wear goggles to protect eyes from dust.
5-5. MECHANICAL PARTS.
5-6. All mechanical parts such as the chassis, side
plates, shields, screws, etc., may be cleaned by
brushing with Federal Spec. VV -K-211b Kerosene or
Federal Spec. O-C-141 Carbon-Tetrachloride. To
remove corrosion use No. 000 sandpaper as well,
then wipe with a clean cloth.
5-7. Dirty gears are cleaned best with a pipe cleaner
or small brush dipped in anyone of the cleaning fluids
mentioned (Refer to paragraph 5-6.). The variable
air trimmer capacitors may be cleaned by soaking
them bodily in anyone of the cleaning fluids (Refer to
paragraph 5-6.), and then blowing them out. This
applies to the r-f trimmer capacitors even when as-
sembled to their isolantite bases, with r-f coils, re-
sistors, and all other fixed capacitors removed.
5-9. RF COILS AND CHOKES. The r-f coils and
chokes used in the radio receiver are all treated by
dipping in bakelite resin, fungicidal varnish approved
as per JAN Spec. JAN-C-l73. The approved thinner
used with this varnish is as per Federal Spec. PTX-
916 Grade B.
5-10. FOUR GANG VARIABLE AIR CONDENSER.
The four-gang variable air condenser end bearings
are lubricated at the factory with Air Force-Navy
Aeronautical Spec. AN -G-15a Grease. It may be lub-
ricated in the remote instance when the need arises.
5-11. AIR TRIMMER CAPACITORS. The variable
air trimmer capacitors are all lubricated at the facto-
ry with Air Force-Navy Aeronautical Spec. AN-G-15a
Grease.
NOTE
Do
not lubricate the variable air trimmer
capacitors even though cleaned as outlined
above (Refer to paragraph 5-7.).
5-12. GEAR TRAIN ASSEMBLY. The reassembly of
the radio receiver gear-train assembly, (Refer to
paragraph 8-2.), subsequent to overhaul, requires
that the Military Spec. MIL-G-3278 Grease, used at
the factory for lubrication purposes, be replaced.
The MIL-G-3278 Grease is applied to the front bear-
ing hub (See 36, figure 4-1.), to the rear bearing
machine screw (42), to the two ball bearings (20), to
the five tempered shafts on the base plate assembly
(43), to the shaft of the flywhee1(22), to the shaft of
the gear assembly (16), and to the shaft of the gear
assembly (24).
7

Section VI
Paragraphs 6-1 to 6-6
AN 16-45-223
SECTION VI
INSPECTION
6-1. GENERAL.
6-2. The radio receiver is inspected, by careful ob-
servation and feel, with regard to any possible physi-
cal indication other than normal. Even though the
receiver mechanical defect appears trivial it must be
repaired at the first opportunity presented so that it
does not tend to develop cumulative receiver abnor-
malities leading to serious failure. As such, inspec-
tion is close ly concerned with preventive maintenance
whereby periodic receiver overhaul provides for
qualified inspection personnel to determine the need
for the immediate repair of the receiver; or, to de-
cide that the nature of the receiver abnormality is in-
significant enough to be taken care of at a later over-
haul date.
6-3. INSPECTION TECHNIQUE. To provide for the
proper inspection of each radio receiver, the inspec-
tor must thoroughly familiarize himself with the re-
ceiver with regard to each of the following considera-
tions.
a. Determine first the normal appearance of the ra-
dio receiver by carefully noting the appearance of
each subassembly and part and their assembled inter-
relationship (Refer to paragraphs 4-1 thru 4-8 and 8-
1 thru 8-3. ). Until such time that the normal detail-
ed appearance of the receiver is committed to mem-
ory compare the receiver part by part with a receiver
known to be in the condition in which it left the facto-
ry. CarefUlly observe the color and finish of all
parts, their relative placement, the dressing of each
electrical wire, the quality of the crimping of each
soldered wire, the amount of solder used to make a
soldered joint, and the manner and location of those
soldered joints providing for electrical ground. Note
that all soldered joints, all r-f coil assemblies, and
all r-f chokes are tropicalized as evidenced by their
brownish fungicidal varnish coating. Note that the
eight nuts at the two escutcheons on the front panel,
the 12 nuts at the six crystal soc kets on the frequency
control unit, the bearing set screw (See 18, figure
4-1.), and each nut used to mount each pin on each of
the
24 r-f tuner coil assemblies, is coated with U. S.
Army Spec. 3-182 Clear Varnish. The varnish is
used as an aid to secure each nut in each instance
since not too much strain can be used to tighten each
assembly.
b. Determine next the manner in which the receiver
operating controls activate the mechanical means
used to perform each control function. Get the feel of
each control and commit it to memory. Note that the
tuning control is flywheel balanced and that it is free
to turn even when the tuning lock is locked. Note that
the two indicators for the main dial and the one in-
dicator for the vernier dial all simultaneously indi-
cate zero dial indications when the four gang variable
air condenser is fUlly meshed. Note that the movable
main dial frequency indicator pointer locates at the
8
frequency scale on the main dial corresponding to the
frequency band indented and whose frequency rang~
is that shown on the dial visible through the small
window contained in the front panel. Note the manner
in which the frequency control unit crystal switch
arm and eccentric drive assembly drives the two
switches coupled to the drive assembly, the orienta-
tion of the drive arm and the effect of the small heli-
cal spring used. Note the spring-return action of the
meter switch. Note the extent to which the gears on
the gear assembly (See 31, figure 4-1.), mesh with
those they engage and the hole provision in the bear-
ing plate (9) to get at one of the screws (32). Note
that the lubrication used on the gear-train assembly
is barely visible. Note by feel the tightness of the
adjustable tuning cores and trimmer capacitors, but
make sure not to disturb their adjustment settings.
6-4. RECEIVER ABNORMALITIES. Inspect the re-
ceiver with regard to each of the following possible
categories of abnormality:
a. AGING. The aging of the receiver is indicated
by the sloppy or non-positive operation of movable
parts whose normal function during movement or
when indented is controlled through the use of springs,
cams, gears, ball bearings, or precise bearing fits
to trued machined shafting.
b. BURNING. The overheating of the receiver is
indicated when parts comprising it show discolora-
tion, blistering, bulging, or smell burnt.
c. LEAKAGE. The evidence of oil or insulating
compound at the terminals of sealed container parts
provide the earliest possible evidence of receiver
leakage. The leakage may be evident too at pin holes
and/or breaks in the container enclosed part itself.
d. CORROSION. The evidence of receiver corro-
sion is the oxidation (rust) which forms on surfaces,
screws, nuts, etc., usually where different metal
areas are in contact.
e. DUST, DIRT, ETC. The need for c leaning the
receiver is evaluated best by the extent to which dust,
dirt, etc., has accumulated at electron tube socket
terminals, resistor boards, and other not too easily
accessible soldered joints and corners in the re-
ceiver.
f. LOOSENESS. The need for tightening any subas-
sembly or part comprising the receiver is evaluated
by feeling the suspected loose part for tightness. In
the instance of attaching hardware such as nuts and/
or screws, consider the assembly tight when no more
than a90 degree turn may be taken up in the attaching
part. Make sure to reseal those nuts listed above
(Refer to paragraph 6-3.), whenever occasion arises
to tighten anyone of them.
6-5. RECEIVER INSPECTION.
6-6. Apart from the careful inspection of the radio
receiver for physical damage evident by observation,

AN 16-45-223
Section VI
Paragraphs 6-7 to 6-12
the receiver controls should all be tried to render
assurance that they function properly. Dependent on
the
inspection appraisal of the receiver on receipt for
overhaul, a decision should be made as to whether or
not the receiver should be turned "on" to determine
the electrical condition of certain of its functioning
parts, before dismantling and disassembly. When-
ever the receiver is turned "on" for inspection, it
should be stripped so that the receiver chassis and
panel assembly may be under observation. Then in-
spect the receiver for the following conditions:
a. Check the r-f gain and the audio gain controls for
noisy operation; if so, replace them.
b. Switch the selectivity switch from position to po-
sition and note if the receiver fault is such as to
cause arcing at anyone of the switch contacts. This
is a very remote possibility but in any case each
switch contact should be inspected for evidence of
charring of the bakelite switch wafers; if any, replace
the switch.
c. Check at all tube sockets terminals for possible
arcing and charring between terminals; if any, re-
place the tube socket concerned. To look at the tube
sockets on the r-f strip, remove the r-f coilassemb-
lies, and use a small dental mirror.
d. Check the conversion switch contacts for arcing
and evidence of charring between contacts; if any,
replace the switch.
6-7. SWITCH, BASE AND SPRING ASSEMBLY. With
the
receiver turned "off", remove the 20 r-f tuner
coil assemblies on five of the six receiver frequency
bands, doing this with the receiver chassis and panel
assembly turned upside down. Engage the pin con-
tacts of the four r-f tuner coil assemblies kept in the
tuning unit assembly with the "V" switch contacts as-
sembled to the isolantite bases contained in the r-f
strip, using the band change control on the front pan-
el. Note to see that the "V" switch contacts are
spread by the pin contacts and that the pin contacts
center up in the "V" switch contacts; also check to see
that none of the "V" switch contacts are broken, or
that the pin contacts in anyone of the 24 r-f tuner
coil assemblies are loose. Replace any broken "V"
switch contacts and tighten any loose pin contacts, if
any.
6-8. SUBASSEMBLY INSPECTION.
6-9. For purposes of receiver overhaul, each sub-
assembly removed from the receiver may be inspect-
ed with regard to each of the following considera-
tions, as applicable.
a. Check the dressing of each part, such as capa-
citors, resistors, coils, chokes, terminal boards,
and the electrical wire lead lengths used. Check the
clearance between parts and their mountings, the en-
coded values and tolerances with regard to resistors
and capacitors; also check the part numbers of coils,
r-f tuner coil assemblies, and the reference symbol
circuit designations on transformer shield assemb-
lies, etc.
b. Check the quality of each soldered joint and the
location and manner of making each specific subas-
sembly ground connection.
c. Check the tightness of staked terminals, screws,
nuts, clamps, and all parts comprising the subas-
sembly. Check each spring for resilience and proper
length, curvature, etc. Check adjustable tuning
cores for proper operation and if bent, noting the e~
tent to which the tuning core in each instance enters
the coil it tunes so that it may be so readjusted prior
to reassembly, thereby not necessitating to much of
an
adjustment during the subsequent alignment.
d. Shake out from the subassembly loose metal and
other particles. Make sure none remain wedged in
the
assembly. Also look closely for metal or other
whiskers, if any, especially as between the stator and
rotor plates of the variable air trimmer capacitors.
Mesh all trimmer capacitors, checking for even
meshing and spacing between plates.
e. Carefully check bakelite and melamine boards
for scratches and cracks; make sure isolantite bases,
insulator feed throughs, and crystal porcelain holders
are not minutely cracked or chipped.
f. Check multiple coil assemblies mounted on the
same form for spacing. Make sure the start and fin-
ish leads on all coil assemblies are properly connect-
ed. Check each coil for continuity and for broken
strands, (one broken strand is permissable). Check
for nicks or scratches on coils and chokes, also
check to see that the fungicidal varnish coating pro-
vided is not punctured.
g. Check the possibility of the parts of the subas-
sembly shorting to other subassemblies or to the re-
ceiver chassis, when assembled. Make sure the pilot
lamps, meter board, etc., mount rigidly.
h. Check to see that the metal finish on each of the
plated parts contained in the subassembly has the
proper finish. Check to see that any excessive fray-
ing of the insulation of electrical wires is cut off and
touched up with U.S. Army Spec. 3-182 Clear Var-
nish.
6-10. PARTS INSPECTION.
6-11. For purposes of receiver overhaul, each part
contained in the receiver, when removed, may be in-
spected with regard to the considerations outlined for
it in one of following classifications. When apart fails
to meet anyone of the considerations listed for it,
reject it, but in instances where the part only requires
cleaning have it cleaned prior to reinspection. All
repaired parts must be reinspected prior to use.
6-12. ELECTRON TUBE INSPECTION.
WARNING
Allow tube
envelopes to cool off before
handling to avoid severe burns, unless hands
are protected.
To inspect each of the electron tubes comprising the
20-tube complement of the receiver, remove the tube
shield, if any, and in the instance of three of the
tubes unclamp the tube clamp retainer associated
with each.
a. Check the firmness of each tube in its socket.
Press the tube into the socket, exerting non other
than normal pressure. When the tube is properly
seated it should be held firmly in place, as evidenced
by feel.
b. Let the tubes cool off before removing them from
9

Section VI
Paragraphs 6-13 to 6-20
AN 16-45-223
their sockets in the receiver. Use the appropriate
tube remover to remove miniature tUbes; also,
straighten the miniature tube pins in the appropriate
pin straightener before trying to insert the miniature
tube into its socket. When inserting the miniature
tube do so with the top of the tube socket visible so
that the tube pins may be properly aligned in relation
to the socket.
c. Inspect the glass or metal envelope of each tube
for dirt or corrosion, as applicable; also check to see
that the tube envelope is not loose. Make sure that
miniature tube pins are not loose or broken, being
careful not to bend the pins during removal or inser-
tion of the miniature tube. Check to see that the glass
envelope is not chipped at the pins.
6-13. RESISTOR INSPECTION. Apart from the vit-
reous-enameled bleeder resistor R85 in the B-recti-
fier supply, which is of the usual lug type and rated
at 12 watts, all the resistors in the receiver are of
the
pigtail, fixed composition insulated type, rated at
1/2, 1/3, or one watt.
a. Inspect the coating of R85 for signs of cracking
and chipping, especially at its ends.
b. Examine the body of each resistor for blistering,
discoloration, and breaks, due to possible overheating.
c. Inspect all resistor leads for dirt, dust, corro-
sion, and looseness. Check the security of all mount-
ings. Once a resistor of the pigtail type is unsolder-
ed, do not reuse in instances where leads were initi-
ally cut short since the point of entry of the lead may
be partially or completely broken, apart from the
fact that resoldering may damage the resistor.
6-14. CAPACITOR INSPECTION. The radio receiv-
er capacitor complement comprises various capaci-
tor types. The four gang eight section main tuning
capacitor, the 24 r-f tuner coil assembly trimmer
capacitors, the delta frequency control capacitor,
and the crystal phasing capacitor are all of the vari-
able air type. For purposes of inspection, the tem-
perature compensatim~, the silver mica molded, the
paper molded, and the oil filled paper tubular capaci-
tors are all classified as of the pigtail lead type,
while the hermetically sealed, dry electrolytic tubu-
lar and bathtub, and paper bathtub capacitors are
classified as of the terminal type.
6-15. VARIABLE AIR TYPE.
a. Inspect the capacitor for dust, dirt, lint, and
poor or broken soldering.
b. Inspect the capacitor plates for visible damage
such as hicks and bending; also, by meshing the rotor
and stator plates, making sure that during meshing
the plates do not touch and that they remain reason-
ably centered at all times with regard to plate spac-
ing.
CAUTION
Never tamper with the plates of the main
tuning. gang condenser.
c. Inspect the capac itor plate mountings, terminals,
and overall with regard to looseness, wear, breaks,
or other damage, making sure that the main capaci-
tor ball bearings and the trimmer capacitor rotor
10
spring assembly in each instance provide for smooth
firm rotor and stator meshing.
6-16. PIGTAIL LEAD TYPE.
a. Inspect each pigtail type lead capacitor for lead
looseness. Do this by applying a firm steady pull to
each capacitor lead in turn, making sure that the ten-
sion applied is not excessive.
b. Inspect each capacitor for discoloration, breaks,
chipping, and evidence that the capacitor molded en-
casing does not completely enclose the capacitor as-
sembly.
c. Inspect the two oil filled tubular metal case ca-
pacitors for evidence of oil leakage at the pigtail lead
solder terminal connections, for the quality of the
solder terminals, and for corrosion.
6-17. TERMINAL TYPE.
a. Inspect the capacitor terminals for insulation
cracks, looseness, corrosion, and evidence of leak-
age of electrolyte with regard to the dry electrolytic
capacitors which may arise when the unit overheats.
b. Inspect the metal case container of each unit for
bulges, dents, cracks, and other damage of any kind.
Make
sure the terminal lugs on the three section
electrolytic capacitor are not loose.
6-18. FUSE INSPECTION. The fuse complement of
the
radio receiver comprises two three ampere hold-
er type fuses, of which one is a spare, and one three-
eighths ampere pigtail type fuse. Throw blown fuses
away.
a. Inspect the pigtail type fuse for loose leads and
both types for loose ends and cracks or breaks in
their glass encasings.
b. Inspect the fuse holder and holder cap for evi-
dence of burning, charring, corrosion, and dirt;
make sure the spring tension in the fuse holder is
strong enough to butt the fuse up against the back of
the fuse cap, noting that the cap spring tension only
provides for holding the fuse to the cap for insertion
or removal.
6-19. INSULATOR INSPECTION. The three insula-
tors used in the radio receiver are of the feed-thru
type. That at the power cable is made of black nylon
and
acts as a strain insulator. That on the frequency
cuntrol unit is made of steatite and has awhite glazed
finish while that on the r-f strip is made of white iso-
lantite.
a. Inspect the steatite and isolantite insulators for
the possible depOSit of foreign matter since an insula-
tor is only as good as the condition of its surface.
b. Inspect the steatite and isolantite insulators for
fine-line surface cracks where moisture and dust will
accumulate and form a leakage path. Make sure these
insulators are clean, without cracks, or chipped in
any way and
that the quality of the soldering and spin-
ning used for mounting is good.
c. Inspect the nylon insulator to make sure that its
physical condition enables it to provide for its strain
function.
6-20. SWITCH INSPECTION. The switch comple-
ment of the radio receiver comprises 11 switches of
which
seven are enc losed and four are open to view.
a. Inspect the mechanical action of each switch and

AN 16-45-223
Section VI
Paragraphs 6-21 to 6-26
look for dirt, dust, andcorrosion on all exposed parts.
In the instance of enclosed switches check the switch
action of the switch by flipping the control knob or
toggle; in the instance of the spring return meter
switch, note the amount of pressure needed to over-
come the spring tension; in the instance of the crystal
selector switch make sure the detent action is posi-
tive acting and that the front panel control knob acti-
vates the frequency control switch contained in the
frequency control unit in each of its seven positions
but only activates the switch 83 on the base plate
(See 43, figure 4-1.), in its most counter-clockwise
position.
b. Inspect the switch base and spring assembly
(Refer to paragraph 6-6.), and the three section
selectivity switch contacts for looseness, dust, dirt,
and corrosion, making sure that the rotors of each
switch make contact with the stators as evidenced by
the visible spreading of the stators when engaged by
the rotors. Do not pry the leaves of the stator con-
tacts apart in any manner whatsoever, other than by
the engagement of the switch rotors themselves.
6-21. RF COIL AND CHOKE INSPECTION. Apart
from the r-f coil contained in each of the 24 r-f tuner
coil assemblies, the radio receiver has an i-f output
autotransformer coil, eight r-f chokes, and 15 r-f
coils, the latter contained in the various transformer
subassemblies comprising the receiver. Four of the
15 r-f coils, contained in the second and driver i-f
transformers, are each further contained in two iron
cups for purposes of shielding. No attempt should be
made to remove said iron cups, the coil assembly it-
se.If is to be replaced whenever the need for the re-
placement of these r-f coils arises.
a. Inspect each r-f coil, r-f choke, and shielded r-f
coil for cleanliness, the quality of soldering, the
firmness of the terminals and the assembly, fungi-
cidal varnishing, no loose coil turns, as applicable.
Make sure that there are no nicks or cracks in the
coil forms or in the fungicidal varnish coatings pro-
vided each coil. Remember that the coil form func-
tions as a high-voltage insulator whose requirement
is the utmost in cleanliness.
b. Inspect each r-f coil and r-f choke for the con-
tinUity of each winding. Check the d-c resistance of
each winding by comparison with the d-c resistance
values of the appropriate new r-f coil or r-f choke,
remembering to make allowance for one broken strand
in the instance of r-f coils wound with litz wire. Note
that the secondaries of the three r-f coils in the r-f
tuner coil assemblies used on the 1. 35-3. 45 me fre-
quency band of the receiver and the four iron cup
shielded i-f coils each use No. 15/44 litz wire. In
all other applicable instances No. 7/41 litz wire is
used.
6-22. POTENTIOMETERS. The radio receiver uti-
lizes potentiometers as r-f gain, audio gain, a-f
meter adjustment, r-f meter adjustment, and bfo in-
jection controls.
a. Inspect the metallic parts of each control for
dust, dirt and evidence of corrosion. Make sure that
the unit has no mechanical defects such as loose ter-
minal lugs, loose body assembly, and a loosely keyed
shaft.
b. Inspect the insulated body of the unit for cracks,
and chipping.
c. Inspect the operation of the control making sure
that the shaft turns smoothly but firmly in its mount-
ing.
6-23. TERMINAL BOARDS. The radio receiver uti-
lizes 15 terminal boardS for purposes of part mount-
ing.
a. Inspect the mechanical assembly of each terminal
board with regard to loose brackets, terminals, eye-
lets, rivets, etc.
b. Inspect the terminal board melamine insulation
for cracks, breaks, dirt, possible charring, or pos-
sible breakdown of the insulation due to the corrosion
of the metal parts of the terminal board assembly.
6-24. CORDS AND CABLES. The main wiring cable,
the a-c power cord, and one three-inch shielded in-
sulated lead cable comprise the cord and cable com-
plement of the receiver. The main wiring cable is
pre-fabricated before assembly to the receiver chas-
sis and comprises, apart from numerous electrical
wires, four shielded insulated lead cables.
a. Inspect the insulation of the a-c power cord, of
each visible electrical wire and cable contained in
the main wiring cable, and that of the three-inch
shielded lead cable, noting whether the insulation is
cracked, deteriorated, cut, kinked due to improper
support, or strained due to improper placement.
b. Inspect the cord and cables at each end of each
lead for broken strands, fraying of the insulation, and
damage due to poor soldering and crimping. Afew
broken strands are not serious but make sure that
many partially or completely broken strands are not
hidden by
the insulation.
c. Inspect to see that the braided shield of the five
shielded insulated lead cables does not short to the
cable lead wires.
6-25. CONNECTORS AND SOCKETS. The antenna
input and the i-f output connectors, the phone jack,
the power and the relay receptacles, the six crystal
and 20 electron tube sockets, comprise the connector
and socket complement of the receiver.
a. Inspect the insulation of each for dirt, dust, cor-
rosion, charring, and cracks.
b. Inspect contacts for collected dust, corrosion,
breaks, and other than normal looseness.
c. Inspect each connector and socket with regard to
the contact provided when its complementary plug,
crystal, or tube is inserted. Increase, when needed
the spring tension of the phone jack. When atube
socket has replaceable contacts and requires replace-
ment, this may prove more practical than replacing
the tube socket.
6-26. METER. The tuning meter contained on the
front panel of the receiver has a100 ma d-c move-
ment and is provided with two scales.
a. Inspect the meter for cracked or broken cover
glass, dents in the case, a warped dial, and bent or
broken pointer.
b. Inspect the meter for dust, dirt, and corrosion
on the meter case and terminals. Remove the meter
cover and repeat the inspection for the inside of the
meter cover and the meter proper.
c. Inspect, by checking the meter adjustment screw,
11

Section VI
Paragraphs 6-27 to 6-33
AN 16-45-223
to see that the pointer may be properly set to the in-
itial dial indication from either direction. Make sure
that the adjustment spring is not caught on the adjust-
ment arm.
d. Test the meter for balance by incorporating it in
a
circuit such that it will indicate ... 20 db on the r-f
scale at 100 ua plus or minus five percent, and will
repeat this test.
6-27. CRYSTALS. The 3.5 me oscillator crystal
and the 455 kc i-f filter crystal, apart from any spe-
cially ordered crystals used for fixed frequency crys-
tal controlled operation, comprise the crystal com-
plement of the receiver.
a. Inspect each crystal for dust, dirt, cracks,
breaks, and corrosion.
b. Inspect the 455 kc crystal terminals, to which
are soldered pigtail type leads, and the 3.5 osc crys-
tal flat strip terminals, to make sure that they are
tight, also inspecting the quality of the pigtail lead
soldering in the instance of the former and the ter-
minal silver plating of both. Make sure that the
cover spring retainer for the 3.5 me osc crystal pro-
vides sufficient tension to firmly seat itself.
c: Inspect the separately ordered crystals for dust,
dirt, dents, poor soldering of metal case, corrosion
of case and pin terminals, cracked terminal pin in-
sulation, and loose terminal pins. These crystals
are ordered according to Military Spec. MIL-C-3098,
are of the Type CR-18/U, but have metal stamped on
the
top and one face side the signal frequency in kc
for which they are intended.
6-28. TRANSFORMERS AND CHOKES. The receiv-
er audio output and power transformers and the two
B-rectifier filter chokes are all of similar container
construction. The power transformer is oil impreg-
nated and hermetically sealed. The audio transform-
er is oil filled. The two filter chokes are hermetic-
ally sealed.
a. Inspect for blistering, bulging, or leakage from
containers and from terminals.
b. Inspect for broken, cracked, or charred insula-
tion at the terminals. Inspect to make sure 'terminals
are not loose.
c. Inspect for dust, dirt, lint, or foreign material
between terminals since same will absorb moisture
which in time provides a leakage path for high voltage
breakdown between terminals.
6-29. FUNCTIONAL MECHANICAL PARTS. The
mechanical parts such as coupling shafts, couplings,
drive arm and eccentrics, gears, lever and roller,
dials, cams, control knob and dial assemblies,
springs, etc" which provide for the proper mechani-
cal functioning of the receiver, all require inspection.
a. Inspect for dust, dirt, and corrosion.
b. Inspect for damage, such as cracks, distortion,
poor etching, etc as applicable.
6-30. MECHANICAL PERFORMANCE STANDARDS.
The
mechanical performance standards of the radio
receiver when subjected to normal use are most
easily evaluated in terms of the minimum (electrical)
performance standards of the receiver; norma.l use
implying that the receiver is not subjected to ex-
treme vibration, extremes in temperature and/or
12
humidity, or exposed to dust, dirt, etc. When the
receiver is subjected to abnormal use, or is dropped,
an evaluation of the abnormalities or damage sus-
tained determine the extent to which the receiver,
certain of its subassemblies, or parts require over-
haul.
6-31. LIFE OF THE RECEIVER. The life of the re-
ceiver is directly dependent on the preventive main-
tenance performed with regard to maintaining the re-
ceiver in its normal mechanical and electrical state.
The replacement of functional mechanical and/or
electrical parts, subassemblies, etc., will not im-
pair the subsequent life of the receiver.
6-32. SERVICE LIMITS. The normal mechanical
requirements of the receiver provide for no allowable
service limits with regard to the mechanical func-
tioning of the receiver parts and subassemblies com-
prising it. The improper mechanical functioning of
the receiver, after long periods of normal use, may
be directly attributable to anyone or more of the
following conditions.
a. Due to accumulations of dust, dirt, sediment,
moisture and the resultant corrosion, rotting, etc.
the mechanical functioning parts of the receiver may
become clogged and subsequently worn so that they no
longer function normally.
b. Due to repeated use and mechanical fatigue, the
attaching hardware used to assemble the parts and
subassemblies to the receiver may loosen up some-
what such that the receiver mechanical functioning
becomes impaired, further use possible resulting in
damage to functioning parts.
c. Due to repeated use and mechanical fatigue, the
numerous springs used in the receiver may no longer
provide the necessary tension required for the normal
functioning of the receiver.
d. Due to the repeated use under conditions tending
to extremes with regard to vibration, temperature,
and humidity, the tendency to other than the normal
mechanical functioning of the receiver may be accel":
erated.
6-33. Whenever the receiver is subjected to over-
haul not directly due to the abnormal use of the re-
ceiver, the overhaul of the receiver should provide
for each of the following checks to be made with re-
gard to the spring complement of the receiver.
a. Check to see that each of the three contact springs
used on the partitions in the tuning unit shield assem-
bly are not loose and make positive contact with the
turret rotor assembly.
b. Check to see that the wavy washer at the front
end of the turret rotor assembly is not loose such
that it fails to turn when the turret rotor assembly is
indented from one band to the next. A loose wavy
washer indicates turret rotor endplay.
c. Check to see that the "U" shaped contact spring
at the rear of the turret rotor assembly provides
firm Wiping contact with the turret rotor assembly
and that it is not loosely mounted.
d. Check to see that the receiver helical spring
complement, namely that at the pointer slide, the two
at . the lever and roller detent assembly, and that at
the conversion switch, have not lost their tension, do-
ing this by removing each in turn and noting that its

AN 16-45-223
Sections VI-VII
unloaded length is normal, i. e., the same as its un-
used counterpart.
e. Check to see that the three spider springs at the
gear-train assembly are not distorted in any way from
their normal unmounted shape by comparing them
with their normal unused counterpart.
f. Check tosee that the 24 r-f tuner coil assemblies,
the 24 r-f coils mounted on them, the six separately
ordered crystals, all adjustable tuning cores, and all
trimmer capacitors, are all provided with sufficient
mounting tension from their respective mounting
springs as evidenced by feel for possible looseness.
g. Check to see that the "V" contact springs on the
band change switch base and spring assembly are not
broken and that they provide contact with the switch
pins on each of the r-f tuner coil assemblies.
SECTION VII
REPAIR AND REPLACEMENT
7-1. GENERAL. The radio receiver comprises parts
of which none should be subjected to repair. How-
ever, all parts comprising the receiver may be re-
placed. Of these the replacement of each of the four
base and spring assemblies, comprising parts con-
tained on the r-f strip, requires further considera-
tion.
7-2. SWITCH BASE AND SPRING ASSEMBLY. To
replace anyone of the four base and spring assem -
blies comprising the stator of the band change switch,
first remove the r-f strip from the receiver. The
reason for the replacement may be that anyone of the
six "V" contact springs on each of the four isolan-
tite bases or the bases themselves, may be broken.
a. To replace a "V" contact spring, the defective
spring is removed by first removing the solder from
the spring terminals which holds the spring in place
in the isolantite base. Then spring back the spring
ear on each spring leg in turn while pushing in a di-
rection to remove the spring. Note the spring ear
locations on the spring to be replaced. Anew spring
is then substituted for the defective spring removed,
solder being used to retain it in place in a manner
evident from any of those contained in anyone of the
isolantite bases.
b. To replace a base and spring assembly use is
made of the line-up bar (See 2, figure 2-1.), and pins
(1,3.), to properly locate the base and spring assem-
bly with regard to its inter-relation to the rest of the
r-f strip assembly. The terminals of the isolantite
base to be replaced are all cleared first by unsolder-
ing the parts and leads soldered between them and the
r-f strip proper. The isolantite base itself is then
unsoldered by removing the solder from the two eye-
lets it contains, and through means of which it is
mounted to the r-f strip. The isolantite base is then
removed so that anew one may be used to replace it.
To properly locate the new isolantite base, the line-
up bar (2) is located over it and the other isolantite
bases contained in the r-f strip. The line-up bar (2)
is then located in relation to the isolantite bases sold-
ered to the r-f strip through means of the pins (1,3)
which fit thru the line-up bar holes and into the two
holes in each of the isolantite bases. Pin (1) is used
in the smaller and pin (3) in the larger of the two
holes in each base. The new isolantite base is then
likewise located so that when soldered into place its
desired position is up against the line-up bar as are
all others. The eight pins and the line-up bar are
then removed and the r-f strip parts and leads pre-
viously unsoldered, are resoldered to the new isolan-
tite base, all dressed as they were previously by dup-
licating an r-f strip kept on hand for purpose of a
sample.
7-3. SELECTIVITY SWITCH. The selectivity switch
which provides three crystal and three non-crystal
positions of receiver acceptance band width is a three
section wafer type switch assembly which is assem-
bled to the receiver with other parts (Refer to para-
graph 4-5.), assembled to it. It is recommended that
the switch assembly be replaced as aunit as compar-
ed to replacing anyone of the wafers comprising it,
the reason being that the switch is purchased as a
unit, the replacement of a wafer being a complicated
procedure due to the fact that its contact construction
assembly is peculiar to the receiver.
7-4. RETROPICALIZATION. The soldered joints,
r-f coils, and r-f chokes in the radio receiver are
all treated with fungicidal varnish to render them
moisture-and fungus-resistant.
a. In the instance of coils and chokes, not other-
wise damaged, but were the tropicalization reqUires
some tOUCh-Up, a small brush dipped in the JAN Spec.
JAN-C-173 varnish, thinned down with approved
thinner as per Federal Spec. PTX-916 Grade B, may
be used to brush the varnish on the coil or choke, as
needed.
b. In the instance of soldered joints, subsequent to
resoldering, each joint is treated with the varnish by
brushing the varnish to completely cover the soldered
joint.
c. In the instance when any soldered joint, even
when not a resoldered joint, is found to be poorly
treated with the varnish it should be retreated to pro-
vide for its complete varnish coverage.
13

Section VIII
Paragraphs 8-1 to 8-2
AN 16-45-223
SECTION VIII
REASSEMBLYING
AND TESTING OF SUBASSEMBLIES AND ASSEMBLIES
8-1. REASSEMBLY. The reassembly of the radio
receiver comprises the separate reassembly of the
receiver chassis assembly and the receiver tuning
unit assembly. The receiver chassis reassembly
need not follow a specific step sequence, other than
that the main cable wiring assembly be added first
and the selectivity switch assembly (Refer to para-
graph 4-5.), be assembled last to the receiver chas-
sis. The frequency control unit and audio filter as-
semblies (Refer to paragraph 4-6.), may be reas-
sembled to the receiver chassis assembly prior to
reassemblying the receiver tuning unit and chassis
assemblies.
8-2. REASSEMBLY OF TUNING UNIT ASSEMBLY.
Before attempting to reassemble the tuning unit as-
sembly, it is recommended that the following step
procedure be understood fUlly so that the various re-
assembly requirements are anticipated during the
actual assembly. The tuning unit assembly com-
prises several subassemblies (Refer to paragraph
4-3.). Of these the gear-train assembly (See figure
4-1.), consists of a tuning unit shield assembly (45)
and a
mounting disk and shaft assembly (35) which
are reassembled subsequent to the addition of the
base plate assembly (43) to the tuning unit shield as-
sembly (45). The gears, parts, etc. which com-
prise the gear-train are then built up on the base
plate assembly (43) to completely reassemble the
gear-train assembly.
a. Reassemble the tuning unit shield assembly (See
43,
figure 4 -1. ), noting that one each of the three
flat springs (46) are associated with each reinforcing
plate of the tuning unit shield assembly (45). The flat
spring (46) is seated on the reinforcing plate prior to
assem bly, the swage tool (See 1, figure 2-2. ), and
mounting (2) being used to swage the reinforcing plate
metal so as to properly seat and firmly retain the
spring.
b. Reassemble the tuning unit shield assembly (45)
to the base plate (43).
c. Reassemble mounting disk and shaft assembly
(35), using the jig fixture (See 1, figure 2 -3. ), the
rod (See 2, figure 2-3.), and the spanner (See 3, fig-
ure 2-3.). The rod is used to line up the eight mount-
ing disks by meshing with the locating holes in each
so that when the fixture is used to seat the mounting
disk and shaft assembly parts, the disk alignment re-
quirements are met prior to tightening the assembly
with the spanner.
d. Reassemble the mounting disk and shaft assembly
(35) to the tuning unit shield and base plate assembly
by locating t~e curved washer (41) on the large nut at
the front end of the mounting disk and shaft assembly
(35) and then seating the combination in the tuning unit
shield and base plate assembly.
e. Add front bearing hub (36) to front end of the
mounting disc and shaft assembly (35) using three
No. 8-32 machine screws (40) and three split lock-
14
washers (39). Also add the machine screw (42), it
acting as the rear bearing for same. Make sure the
curved washer (41) is centered on large nut at front
end of the mounting disk and shaft assembly (35) be-
fore tightening the two bearings. Lubricate both
bearings using Military Spec. MIL-G-3278 Grease.
f. Use rod (See 2, figure 2-3.), to line up mounting
disk and shaft assembly and tuning unit shield and
base assembly, through means of the alignment holes
in each, so that the conversion switch cam at the
rear of HIe mounting disk and shaft assembly is in its
high position when the switch blade of the conversion
SWitch, assembled to the tuning unit shield assembly,
shorts its center fixed contact to its fixed contact
closest to the edge of the tuning unit shield assembly.
g. Add the two loop type springs (44) to the top of
the base plate assembly (43) and add the anchor plate
(33) for the r-f strip, using two No. 6-32 machine
screws (34), to the base plate (43).
h. Add
the large spur type gear (37) and the small
spur type gear (38) using three No. 8-32 machine
screws (40) and three split lockwashers (39), to the
hub (36).
Also add the gear assembly (31), using two
No.
6-32 machine screws (32), to the bottom left side
of the base plate (43), but do not tighten the assem-
bly.
i. Add the three mounting posts (7) using three No.
10-32 machine screws (11).
j. Add the gear assembly (21) by locating it to the
ball bearing (20) at the base plate assembly (43) pro-
vision for same with Military Spec. MIL-G-3278
Grease, and to the other ball bearing (20), located
with grease, at the bearing set screw (18) mounted on
the bearing plate (10) by the nut (19); and then holding
it in place by mounting the bearing plate (10), carry-
ing the lubricated loosely mounted gear assembly (16),
to the two top posts (7) using two No. 10-32 machine
screws (11).
k. Lubricate, using Military Spec. MIL-G-3278
Grease, the five tempered shafts on the base plate
assembly (43).
1. Locate the drive pin assembled to the gear assem-
bly (21), by turning the latter so that the drive pin is
at the top of the slot in the base plate assembly (43).
Add
the two spur type gear assembly (26) to the spider
assembly at the top right of the base plate assembly
(43) and mesh with the vernier dial spur type gear
(27), added to the adjacent shaft contained on the base
plate assembly (43), so that the stop pin of the spur
type gear (27) is radial with the center of the two spur
type gear assembly (26) and against one of the buttons
contained thereon when the spur type gear (27) is turn-
ed clockwise. Now back away the gear assembly (21)
so that the drive pin contained thereon is one tooth
(maximum of two teeth) away from its position at the
top of
the slot in the base plate assembly (43), and
mesh in this position with the two spur type gear as-
sembly (26). Having engaged gears in this manner
install "C" washer retainer rings (30), one on each

AN 16-45-223
Sections VIII-IX
of the shafts, namely the spider shaft and the shaft
adjacent to it. Use the pliers (See 1, figure 2-4.),
to tighten the retainer rings.
m. Add the spur type gear (28) to the top left spider
on the base plate assembly (43). Also add the main
dial hub spur type gear (29) to the shaft adjacent to
the spider. With the vernier dial spur type gear (27)
so that its stop pin is up against button stop as out-
lined above (Refer to paragraph 8-2.), the upper tap-
ped hole in the main dial hub spur type gear (29) is
located so that a straight edge bisects said tapped
hole when the straight edge is butted up against the
shafts which carry the main dial hub spur type gear
(29) and the spur type gear (28). Add retainer rings
(30) one each to the shafts carrying gears (28) and
(29).
n. Add
idler wheel (23) to the bottom spider on the
base plate assembly (43). Lubricate the shaft of fly-
wheel (22) and the shaft of gear assembly (24) using
Military Spec. MIL-G-3278 Grease, add the cam (25)
to the latter and mount all of same with the bearing
plate (9), using one No. 10-32 machine screw (11) for
the bottom post (7), and two No. 8-32 machine screws
(12).
o. Add the
band change cam detent roller and lever
assembly (6) and the two helical springs (5) for same.
Bring cam (25) forward to bearing plate (9) and locate
cam in roller, lining up cam with the roller and lever
assembly (6), arm, and then tighten the set screws in
the cam (25).
p.
Check for smooth overall operation and then
tighten the two No. 6-32 machine screws (32) which
are used to mount the gear assembly (31).
q.
Adjust bearing set screw (18) mounted on the
bearing plate (10) for no slack but make sure mount-
ing tap is not bent out during the adjustment.
r. Tighten the three machine screws (17) which
mount the hub of the gear assembly (16) to the bear-
ing plate (10) so that the gear of the gear assembly
(16) meshes properly with the small spur type gear
(38) mounted on the front bearing of the mounting disk
and shaft assembly (35).
s. Add the movable support main pointer bracket
(15), the four retainer disks (13), mounted by the four
No. 4-40 machine screws (14) providing for position-
ing the movable bracket (15). Also add the indicator
slide helical spring (2).
t. Add cam, hub, and band change dial assembly (1),
locating dial so that hairline on it lines up with that
on the jig used (See 2, figure 2-4.), which is mount-
ed for this purpose over the assembly (1) on the mov-
able bracket (15) and its mounting.
u. Add
main and vernier dials, and dial indicator
pointers, setting dials to the indicators so that both
dials start from zero dial indication. Add main dial
pointer to movable bracket (15) with the pointer set
to the main dial first frequency mark line.
8-3. RESOLDERING AND RETROPICALIZATION.
The reassembly of the radio receiver requires that
all electrical wires which were unsoldered, to dis-
mantle and disassemble the radio receiver, be re-
soldered. Subsequent to resoldering each soldered
joint must be completely covered with fungicidal var-
nish, approved as per JAN Spec. JAN-C-I73, by
brushing each joint with a small brush dipped in same.
To maintain performance, all electrical wires and
part lead lengths, the electrical wires pre wired to
subassemblies and parts, their dressing and the
dressing of all parts, the manner and location of each
ground connection, must duplicate in each instance
the factory techniques incorporated into each radio
receiver.
8-4. TESTING OF SUBASSEMBLIES AND ASSEM-
BLIES. The test procedure used with regard to a
receiver subassembly is to reassemble the repaired
subassembly or anew one to the receiver and then to
test the radio receiver as outlined in the applicable
Handbook of Service Instructions.
SECTION IX
REASSEMBLY AND TESTING OF COMPONENTS
9-1. REASSEMBLY. The reassembly sequence of
the radio receiver is to reassemble the subassem-
blies comprising it separately and then, in turn, to
reassemble the subassemblies into an assembly to
which is added the bottom plate and top cover. The
subassemblies themselves comprise sub-subassem-
blies some of which only involve the addition of parts
to other parts to facilitate their subsequent subassem-
bly assembly (Refer to paragraph 4-5. ).
9-2. REASSEMBLY OF THE CHASSIS AND TUNING
UNIT ASSEMBLY.
The procedure to reassemble the
chassis and tuning unit assembly is to add the tuning
unit assembly (Refer to paragraph 8-2.), including
the gear-train assembly and the tuning unit shield as-
sembly, to the chassis assembly (Refer to paragraph
8-1.), in the following manner.
a. Seat the tuning unit assembly into the chassis as-
sembly.
b. Fasten the tuning unit assembly at its rear end to
the chassis assembly, using aNo. 10-32 machine
screw with included external-tooth washer, by pass-
ing the sc rew thru the angle brae ket on the tuning unit
assembly and thru the hole in the chassis assembly,
and then adding aNo. 10 lockwasher and aNo. 10 nut
to the No. 10-32 machine screw.
c. Fasten the tuning unit assembly at its front end
to the chassis assembly, using two No. 10-32 machine
screws with included external-tooth lockwasher, and
one stud screwed into a spacer post, at either front
side of the tuning unit assembly, by passing the two
screws and the stud thru clearance holes in the chas-
sis assembly to screw into two nut plate brackets used.
15

Section IX
Paragraphs 9-3 to 9-5
AN 16-45-223
Table 9-1. Identification of the R-F Tuners
HAMMARLUND PART/DRAWING NO.
BAND MC
FREQ
NO. RANGE INPUT INTERSTAGE OSCILLATOR
1
0.54-1. 35
31387-1 31386-1 31386-1
31385-1
2
1.35-3.45 31390-1 31389-1
31389-1 31388-1
3
3.45-7.40
31393-1 31392-1 31392-1
31391-1
4
7.40-14.80
31396-1 31395-1
31395-1
31394-1
5 14.80-29.70 31399-1 31398-1 31398-1 31397-1
6 29.70-54.00 31405-1 31404-1 31404-1
31403-1
d.
Resolder two red/green, one green/red, and one
yellow Ired lead of the main wiring cable to the S4
conversion switch.
e. Resolder one white/black, one red/white, one
blue/red, one yellow/black, and one red/green lead,
comprising leads from the terminal board E13 adja-
cent to the filter assembly, to the top terminal strip
of the mixer plate transformer assembly T1 on the
tuning unit assembly.
f. Resolder the two blue/black leads of the tuning
unit assembly to the T2 second mixer input trans-
former.
g. Resolder the two green/white leads of the tuning
unit assembly, one to the E17 terminal board at the
front of the chassis assembly alongside the selectivity
switch and the other to the E14 terminal board normal
to the former at the front end of the switch.
h. Retropicalize all soldered joints (Refer to para-
graph 7-4.).
9-3. REASSEMBLY OF THE CHASSIS AND PANEL
ASSEMBLY. The procedure to reassemble the chas-
sis and panel assembly is to assemble the receiver
front panel assembly to the chassis and tuning unit
assembly (Refer to paragraph 9-2. ), in the following
manner.
a. Fasten the front panel assembly to the chassis
and tuning unit assembly using eight, one inch No.
10-32 machine screws, four on each side of the front
panel, and two, half inch No. 10-32 machine screws
at the bottom of the front panel, the latter screwing
into the spacer posts used in the reassembly of the
tuning unit assembly to the chassis assembly. Each
No. 10-32 machine screw has aNo. 10 lockwasher
added to it.
b. Relocate all toggle switches and the phone jack
and fasten each to the front panel using the nut locat-
ed on the shaft bushing of each, during disassembly.
c. Relocate all four flexible couplings to engage
their respective shafts contained in the front pane Iand
tighten the set screws contained in each.
d. Add the r-f gain, tuning, band change, and audio
gain knobs to the appropriate control shaft of each
and tighten the set screws contained in each.
e. Assemble the small eccentric, the large eccen-
tric, and tie rod, which together provide the drive
assembly for the S3 crystal switch located on the base
16
plate of the gear-train assembly, and add the large
eccentric to the extension shaft of the S2 crystal se-
lector switch. Now locate the extension shaft into
the fixed coupling at the frequency control unit and
through the clearance hole for it in the front panel.
Seat the small eccentric on the shaft of the S3 crystal
switch and locate the tie rod so that it is normal to
the extension shaft. Tighten the set screws in the
fixed coupling and those on the small and the large
eccentric so that when the crystal selector switch S2
is in its most counter-c lockwise position, the crystal
switch S3 is also in its most counter-clockwise posi-
tion. Add the small helical spring to the S3 crystal
switch and the knob to the extension shaft at the front
panel.
9-4. REASSEMBLYOF THE RADIO RECEIVER. The
final step in the reassembly of the radio receiver is
to add the bottom plate and then the top cover to the
chassis and pane 1 assembly (Refer to paragraph 9-3.),
in the following manner.
a. Reassemble the bottom plate using seven No. 10-
32 machine screws with included external-tooth lock-
washers.
b. Reassemble the top cover inclUding a rubber
packing strip, by butting the rubber packed end of the
top cover up against the panel of the chassis and pan-
el assembly while tightening the four No. 6-32 mach-
ine screws including external-tooth lockwashers,
each of which passes thru one of the four mounting
brac kets which form part of the top cover proper.
9-5. REASSEMBLY OF THE RF TUNERS. The 24
r-f tuners or r-f coil assemblies are subassemblies
which are considered part of the tuning unit assembly.
proper. Even so they may be reassembled to the
chassis and tuning unit assembly or to the chassis
and pane I assembly, preferably to the latter. Each
r-f tuner has stamped on its steatite base the Ham-
marlund part/drawing number applicable to it. Table
9-1 identifies each r-f tuner so that it may be pro-
perly reassembled to the chassis and panel assembly
of the receiver. For each frequency band the input
r-f tuners are reassembled to the rear end of the
rotor and mounting disk assembly contained in the
tuning
unit assembly. Next in reassembly sequence
are the two interstage r-f tuners, the oscillator r-f