Graybar 600 Operating and maintenance manual

RADIO
GRAYBAR600
SERVICE NOTES and
REPLACEMENT PARTS
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GraybaR
ELECTRIC COMPANY

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CONTENTS Page
Introduction_ 5
Radiotron Sequence .7
Service Data Chart.... 39
Replacement Parts 40, 41, 42
PART I -INSTALLATION
Antenna (Outdoor Type)
Antenna (Indoor Type)
Special Antenna Installations for Noisy
Locations
Ground
Radiotrons
Receiving Loud Local Stations.
Page88
8101011
Page
Adjustment for Low Line Voltages__ ___ 12
"Local -Distant" Switch________ ..... .... 12'
Jerky Action of Station Selector................._______ 12
Installation of Pilot ...... 12
Phonograph Pick -Up.... 13
Location of Receiver in Room. 13
Knobs 13
PART II -SERVICE DATA
Antenna System Failures
Radiotron Sockets
Radiotron Prongs
Loose Volume Control
Broken Condenser Drive Cord
Radiotrons Fail to Light When Operating
Switch Is "On" ___-_____ ..... ...... 15
Plates of Radiotron UX-280 Excessively Hot 15
No Signal-Radiotrons 0 K. 15
Hum 16
Low Volume 16
Audio Howl 17
Acoustic Howl .. 17
Distortion in Reproducer Unit Only 18
14 Adjustment of R.F. Compensating Con -
14 denser - 18
14 Distorted Reproduction Caused by Other
14 Than Reproducer Unit - 18
14 Adjustment of I.F. Transformers 19
Adjustment of Oscillator Trimming Con -
Testing Electrical Alignment of Tuning
Condensers
Audio Transformer and Receiver By-Pass,
Condensers
Output Condenser, Output Choke and Filter
Condensers
Reproducer Unit ..
Centering Cone of Reproducer Unit
PART III -ELECTRICAL TESTS
Voltage Supply System 25
Voltage Readings at Terminal Strip 25
Voltage Readings at Radiotron Sockets 25
Methods for Continuity Tests 26
Receiver Assembly Continuity Tests 29
Socket Power Unit Continuity Tests _
Checking Resistance Values
Testing By -Pass Condensers
Testing for Grounded Parts in Receiver
Assembly
PART IV -MAKING REPLACEMENTS
Replacing the Volume Control
Replacing R.F. Transformer and Oscillator
Assembly
Replacing Radiotron Gang Sockets
Replacing Main Tuning Condensers and
Drive
Replacing Condenser Drive Cord ...........
Replacing R.F. Compensating and Oscillator
Trimming Condensers ... ...... .......... ....... 34
Replacing the Audio Transformer and By -
Pass Condensers ..... ....... _ ...... ....... ......
Replacing Perforated Dial Scale
Replacing Power Cable
Replacing Intermediate Transformers
Model No. 600 Receiver
Rear Interior Cabinet View
Top View of Receiver Chassis
Top View of S.P.U. 6
Radiotron Sequence 7
Sub -Chassis View of Receiver 9
Schematic Circuit of No. 600 Receiver 10-11
Dial Screen, Tuning Scale, and Pilot Lamp 12
Schematic of Phonograph Pick -Up 13
Tuning Condenser Drive Cord 14
Non -Metallic Screw Driver .15
Adjusting Compensating and Oscillator Trim-
ming Condensers 15
175 K.C. Test Oscillator 17
Adjusting I.F. Tuning and Neutralizing.
Condensers 19
21
22
23
232424
303131
31
32 Replacing Tapped Resistance Unit in Receiver
Assembly
33 Replacing Miscellaneous Parts in Receiver
33 Assembly
Replacing Cone of Reproducer Unit
34 Replacing Output Transformer
34 Replacing Filter Condensers, Output Con-
denser and Output Choke
Replacing Power Transformer or Filter Re -
35 Replacing Terminal Strip on S.P.U. or Re -
35 ceiver Assembly
35 Replacing Miscellaneous Parts in S.P.U.
36 Replacing Front Grill Panel or Cloth...._....-...........
ILLUSTRATIONS
145
36
363637
37
37
383838
I.F.Condenser Adjusting Screws 21
Adjusting Oscillator Trimming Condensers 22
Aligning Tuning Condensers 23
Aligning Tool 23
Centering Cone ,24
Schematic of Voltage Supply System 25
Internal Connections of Audio Transformer
and By -Pass Condensers 26
Internal Connections of Output Choke, Out-
put Condenser and Filter Condensers . 26
Cable Connections 27
Receiver Sub -Chassis Wiring Diagram .........-. .... 28
S.P.U. Wiring Diagram 30
Removing Reproducer from Cabinet.. 32
Removing Receiver from Cabinet 33
Removing Grill Panel from Cabinet 35
3

SOCKET POWER
UNIT
SPARE PILOT
LAMP SOCKET
ANTENNA AND
GROUND
BINDING POSTS
Figure 1-Rear interior cabinet view showing
location of main assemblies
4
DYNAMIC REPRODUCER
ASSEMBLY
RECEIVER CHASSIS
ASSEMBLY

Grayb aR
No. 600 RECEIVER
SERVICE NOTES
INTRODUCTION
The Graybar No. 600 receiver is a seven -tube socket powered console cabinet model
radio receiver utilizing the Super -Heterodyne circuit in its highest development, and em-
ploying six UY-227 Radiotrons and the newly developed power amplifier Radiotron, UX-245.
The Radiotron UX-280 is used in a socket power unit for supplying all plate, grid, and
cathode voltages as well as supplying a high D.C. voltage for the newly developed high
voltage, low current dynamic reproducer field used in this receiver. Incorporated in this
receiver are the latest developments in Super -Heterodyne engineering in addition to other
perfected features such as one -dial control, complete A.C. operation, power detection, single
audio amplification stage, with overall balance in sensitivity, selectivity and tonal quality
that can best be accomplished in a Super -Heterodyne. Figure 1 illustrates a rear view show-
ing the principal parts. Figure 2 illustrates the top view of the receiver chassis, and Figure
3 is a view of the socket poiyer unit.
PERFORAtED CELLULOID
DIAL DIAL SCREEN
STATION
SELECTOR DRIVE
ANTENNA AND
GROUND LEADS
PILOT GANG CONDENSER A. F. TRANSFORMER AND
LAMP ASSEMBLY BY-PASS CONDENSERS
CABLE TO S. P. U.
SERIAL R. F. COMPENSATING SERIES OSCILLATOR PARALLEL OSCILLATOR PHONOGRAPH PICK-UP
NUMBER CONDENSER TRIMMING COND. (600 K. C.) TRIMMING COND. (1400 K. C) TERMINAL STRIP
Figure 2-Top view of receiver chassis showing principal parts
The No. 600 receiver is designed to operate on alternating current of 105 to 125 volts,
50 to 60 cycles as used for house lighting. Connection to D.C. lines or to A.C. lines of
different rating may damage the receiver or the Radiotrons.
This receiver is also made in models designed for alternating current operation of 105
to 125 volts, 25 to 40 cycles. In this model the power transformer is different from that
used in the 50-60 cycle models. All other parts are identical in both models and the Service
Notes apply to each equally well.
The following circuit characteristics are incorporated in the No. 600 receiver:
(a) The six UY-227 Radiotrons and one UX-245 Radiotron are connected in a seven -
tube super -heterodyne circuit with a UX-280 Radiotron in the S.P.U. for plate,
grid, and cathode voltage supply as well as high voltage, low current supply to the
field of the new dynamic speaker.
5

55
The super -heterodyne circuit consists of one tuned R.F. stage; tuned fitst de-
tector; two intermediate R.F. stages; an oscillator; a second, or power detector;
and the single audio stage using the recently developed power amplifier litictiotron
UX-245. The Radiotron sequence is shown in Figure 4. 4
(b) A "Local -Distant" antenna switch is incorporated in this receiver which permits
better control of volume with less distortion, due to the natural condition of over-
loading on extremely loud local signals together with better selectivity on local
stations. This feature with the use of a high impedance semi -tuned primary induct-
ance of the tuned R.F. stage permits the use of a varying length of antenna without
materially affecting the tuning of the receiver.
(c) The intermediate radio frequency (referred to as I.F.) which results from the
mixing of the incoming modulated radio frequency current with that of the local
oscillator is 175 K.C. The audio, or voice, modulation that is present in the radio
frequency is carried on through the first detector and in the mixing is impressed
on the I.F. After being amplified in two I.F. stages it is detected, or rectified, and
POWER OUTPUT CHOKE, OUTPUT CONDENSER,.
TRANSFORMER AND FILTER CONDENSERS FILTER
REACTORS
TERMINAL
STRIP
A. C. POWER INPUT UNE UK -280 OPERATING
(PLUG NOT SHOWN) SOCKET SWITCH
Figure 3-Socket power unit showing
principal parts
further amplified in the audio amplifier stage using the new Radiotron UX-245.
'I'he use of 175 K.C. for the I.F. prevents serious harmonic disturbance around
550 K.C., which is a distinct asset. The super -heterodyne circuit owes its superior
selectivity and sensitivity to tuned I.F. amplification, for no matter what the R.F.
frequency may be to which the receiver may be tuned the most part of the over-all
amplification is accomplished by the uniform amplification of the I.F. stages. These
I.F. stages are also constantly neutralized for 175 K.C. Neutralization, or preven-
tion of oscillation, is then independent of the broadcast frequency, which is prac-
tically the ideal condition for radio reception. The I.F. transformers are sharply
tuned to give improved over-all selectivity. The tonal quality is maintained by
means of certain refinements in the circuit arrangement, especially at high fre-
quencies.
(d) The second detector operates at 235 volts plate potential with proper grid bias.
The high plate voltage used gives sufficient undistorted output to operate the single
audio power stage using the UX-245 Radiotron directly from the second detector,
thus eliminating any possible distortion that might be caused by an intermediate
audio stage.
(e) Use of the UX-245 Radiotron with the new dynamic speaker permits an undistorted
output which represents an over-all gain over previous receivers. It uses the same
6

( f )
(g)
voltage on its filament as the UY-227, and plate and grid voltages that fall within
the supply limits of a UX-280.
The volume control regulates the grid bias on the tuned R.F. stage and the first
I.F. stage. When loud local signals are received the "Local -Distant" switch in the
local position acts very effectively in allowing better control of volume near the
maximum volume control setting without over -loading the receiver. The volume,
when the over -loading point is reached, will, of course, distort and drop to a small
value. This is entirely natural to the over -loading condition in a vacuum tube, as
is also the two peaked tuning effect, which is obtained when the dial is detuned to
either side of the normal peak setting with resultant less input and hence no over-
loading.
The use of a high voltage, low current field in the dynamic loudspeaker employing
the 8 -inch cone makes a sensitive reproducer with a field that is supplied by the total
D.C. voltage output of the UX-280 in the S.P.U., drawing only approximately 46
milliamperes at about 300 volts. This load together with the receiver Radiotron load
is much below the load limit of the UX-280. The voltages on the plates, as well as
the grid voltages of the R.F. and I.F. Radiotrons, are purposely reduced to make no
over-all difference in amplification, but permitting better S.P.U. regulation and
stabler operation. Proper cathode voltages are supplied to all the UY-227 Radio -
FROM ANTENNA
32
POWER 2.20iTPWR.) OSC. 2W F. LE I. F. TUNED IL' TUNED
A. F. DET. R. F.
RADIO FREQUENCY CURRENT
-- - OSCILLATOR
TO R. F. CURRENT IN INTERMEDIATE STAGES
LOUDSPEAKER A. F CURRENT
Figure 4-Radiatron sequence
trons to secure quiet operation and insure average Radiotron life. For the most
part, the series or parallel resistance method of supplying voltages is used. The
line voltage adjustment switch, common in most receivers, has been discarded to
make necessary a more careful check of the supply line voltage before making any
change. A tap has been provided in the power transformer primary, located under
the S.P.U. for lower than 115 -volt power supply to which a soldered connection can
be made. This will prevent frequent change -over in the power supply and thus
will lessen the application of excessive filament voltages.
Mechanical and electrical improvements not mentioned above are :-
(a) Use of "Isolantite" for I.F. transformer adjustable condenser and coil mounting,
and also the R.F. compensating and oscillator trimming condenser mounting.
(b) Accessibility of I.F. adjustments. See Part II, Section 16.
(c) Electrostatic shielding between R.F. condensers of the gang tuning condenser and
also between socket power unit and receiver chassis.
(d) Simplified construction of the S.P.U.
(e) Projection type of dial scale with kilocycle designation is distinctly a new feature.
(f) A terminal strip is provided for convenient use of a phonograph pick-up.
RADIOTRON SEQUENCE
Figure 4 illustrates the Radiotron sequence. Radiotron No. 1 is a stage of tuned radio
frequency amplification. It is coupled to the antenna and ground by a high impedance
primary inductive coil. It is tuned by the first of the gang condensers located at the right
and facing the receiver from the front.
Radiotron No. 2 is the tuned heterodyne detector. It is tuned by the center of the gang
condensers. 7

Radiotrons No. 3 and No 4 are the first and second intermediate frequency stages re-
spectively. These stages are tuned to a frequency of 175 K.C., giving ample distance between
the two peaks of the oscillator to eliminate any possibility of stations coming in at more than
one point on the tuning dial.
Radiotron No. 5 is the oscillator. It is tuned by the third of the gang condensers. Two
trimming condensers are provided at the rear of the receiver assembly for adjusting the
oscillator circuit to keep the beat note at the correct frequency for the intermediate fre-
quency stages.
Radiotron No. 6 is the second detector. It operates at a plate potential of 235 volts
with the proper grid bias and does not use a grid leak or condenser. Its output is sufficient
to drive the power amplifier.
Radiotron No. 7 is the power amplifier. A choke and condenser arrangement couples
this tube to the step-down transformer that matches the impedance of the output circuit to
that of the cone coil of the reproducer unit. This arrangement gives a quality of repro-
duction not obtainable with the use of an output transformer alone, and prevents flow of the
D.C. plate current of the UX-245 through the output transformer primary.
These various principles incorporated in the No. 600 receiver are illustrated in the
schematic circuit Figure 6. PART I-INSTALLATION
[ 1 ANTENNA (OUTDOOR TYPE)
Due to the high sensitivity of this receiver the antenna length need be only 25 to 50
feet. In remote districts this length may be extended to secure improved pick-up of distant
broadcasting stations. However, a natural corresponding decrease in selectivity when receiv-
ing from local stations will be experienced with the longer antenna, provided the "Local-
Distant" switch is not in the local position.
It should be erected as high as possible and be removed from all obstructions. The
lead-in should be a continuation of the antenna itself, thus avoiding all splices which might
introduce additional resistance and, in time, corrode sufficiently to seriously affect reception.
If it is absolutely necessary to splice the lead-in to the antenna the joint must be carefully
soldered to insure a good electrical contact. Clean off all excess flux and tape the connection,
to protect it from the oxidation effects of the atmosphere.
High-grade glass or porcelain insulator supports are required, and at no point should the
antenna or lead-in wire come in contact with any part of the building. Bring the lead-in
wire from the outside through a porcelain tube insulator to the inside of the house for con-
nection to the receiver.
The antenna should not cross either over or under any electric light, traction, or power
line and should be at right angles to these lines and other antennas. An outdoor antenna
should be protected by means of an approved lightning arrester, in accordance with the
requirements of the National Fire Underwriters' Code.
[ 2 ] ANTENNA (INDOOR TYPE)
Where the installation of an outdoor antenna is not practical, satisfactory results may
generally be obtained by using an indoor antenna of 25 to 50 feet of insulated wire strung
around the picture moulding or placed under a rug. In buildings with steel framework or
where metal lathing is employed, satisfactory results are not always possible with this type
of antenna. However, due to its sensitivity, the No. 600 receiver will generally give entirely
satisfactory reception with an indoor antenna.
[ 3 ] SPECIAL ANTENNA INSTALLATIONS FOR NOISY
LOCATIONS
In line with other receivers, when the No. 600 receiver is installed in some city locations,
such as apartment houses, hotels and office buildings, it is possible that the level of noise
compared with the signal strength of the desired station may be such that the station cannot
be received without an objectionable noise background. This noise may be defined as inductive
interference from electrical devices such as elevator motors, generators, violet ray machines,
professional equipment, etc. It may have no apparent radio frequency peak, or it may have
a broad peak. The effect of the noise may be divided into the following three general classes :
3

(a) Where the noise level is zero with no antenna or ground, but is equally great on
either an indoor or outdoor antenna.
(b) Where the noise is equally great with the antenna and ground either connected or
disconnected.
(c) Where the noise level is greater when the outside antenna is connected than when
an inside antenna is used ; the inside antenna, however, not giving sufficient pick-up
for satisfactory reception.
In (a) where the noise level is zero with no antenna or ground connected, but equally
great with either an indoor or outdoor antenna, it is at once apparent that the interference
is not being brought into the receiver over the power supply lines. It has been found in
such cases that an antenna five feet long inside the room picked up as much noise as when
an entire outside antenna lead -in were used. This indicates that the noise is within the
building and, in the case of the outside antenna, is being picked up on that portion of the
lead-in that enters and goes through the building. In such cases the receiver should be
located close to the point where the outside lead-in enters the building. If this is impractical
it can be placed in any location and a copper braid, such as that manufactured by Belden
Mfg. Co. of Chicago, Ill., placed over the inside portion of the lead-in wire. This braid is
not grounded. If the noise level is still appreciable a good receiver ground with a short lead
must be obtained. A long lead is not desirable, as it may pick up noise.
R. F. AND OSCILLATOR
COIL ASSEMBLY
GROUND CONNECTION
TO FRAME
ANTENNA
GROUND
LEAD RESISTOR DIVIDING RES. I. F. TRANSFORMERS RESISTOR
OSCILLATOR OSCILLATOR SERIES R. F. BY PASS UX-245 GRID
GRID CONDENSER FIXED CONDENSER CONDENSER BIAS RESISTOR
OSCILLATOR OSCILLATOR FILAMENT CENTER -
GRID LEAK GRID RESISTOR TAPPED RESISTOR
A. F. TRANSF.
PRI. RESISTOR
A. F. TRANSF
SECONDARY
CONDENSER
A. F. TRANSF
SEC. SERIES
RESISTOR
BLEEDER VOLTAGE N2 1 AND N. 2 YE' I. F. PRI. ti \ VOLUME Ne 3 I. F.
CONTROL TRANSFORMER
Figure 5--Sub-chassis view of receiver showing principal parts
In (b) the noise is picked up with no antenna or ground connected to the receiver. This
indicates the noise is entering the receiver through the power lines. In this case filters must
be placed in the power supply at the source of the noise or at the receiver, depending on
conditions. If the trouble is cleared up in this manner when the antenna and ground are
disconnected, but again appears with the use of the antenna system, the remedies suggested
in (a) must also be applied.
In (c) the noise is greater when the outside antenna is connected than when an inside
antenna is used. The use of the inside antenna, however, does not give sufficient pick-up for
satisfactory reception. In this case the pick-up is probably occurring on the lead-in wire
between the receiver and the antenna. Copper braid should be placed over the entire lead-in
from the receiver to the flat portion of the antenna. Also changing the direction of the
antenna should be tried and the lead-in connected from the end of the antenna that gives
the best results. The copper braid should not be grounded. The conditions existing in any
locality must be analyzed and placed in its correct category. A little patience and experi-
menting will usually result in a satisfactory installation.
RCA type "A" line filters may be used where the interfering line apparatus draws up
to 2.5 amperes at 110 volts A.C. or D.C. For larger apparatus drawing current from 2.5
amperes to 5.0 amperes, RCA type "B" line filter may be used.
9

[ 4 ] GROUND
A good ground is quite as important as a good antenna. No specific recommendations
can be given in this matter as conditions vary in different locations. Water and steam pipes
usually make good grounds. Gas pipes usually make poor grounds and, as a rule, are to be
avoided. If neither water nor steam pipes are available, a pipe or metal rod may be driven
into the ground to a depth of several feet. The success of this type of ground depends upon
the moisture present in the soil. The ground lead should be as short as possible and con-
nected by means of an approved ground clamp to a section of pipe that has been scraped and
thoroughly cleaned. The connection should be inspected from time to time to make certain
that a clean and tight electrical contact exists between the clamp and pipe. The service man
should experiment with various grounds, and employ the one giving the best results.
icy LOCAL -DISTANT
/SWITCH
UY 227
TUNED R f
R F
COMPENSATING
CONDENSER--_
C
g gc=iOO7
.___If.
0.5 if
MFD-
UT 227DET
GROUND LEAD AND
ALL OTHER GROUND
CONNECTIONS ARE
CONNECTED TO FRAME
0.0008
MFD
-OO
3,00011 UT 227
OSC
[ 5 ] RADIOTRONS
A guide shield is provided on all the receiver Radiotron sockets to facilitate the insertion
of the Radiotrons. The six Radiotrons UY-227 are inserted in the five -contact sockets. The
Radiotron UX-245 is placed in the four -contact socket in the receiver assembly, and the
Radiotron UX-280 is placed in the socket power unit.
In placing the receiver into operation, if no signals are heard when tuning to a station
known to be broadcasting, examine the Radiotrons. Possibly one Radiotron has been dam-
aged in transit. Interchanging with one or more of the same type known to be in operating
condition will isolate the damaged one.
NoTE.-Socket No. 1 (Figure 4), the tuned R.F. stage, is the most critical for selection
of the Radiotrons. Place in this socket the tube which gives the loudest signal and does not
go into oscillation throughout the tuning range. If no tube is found that will not oscillate,
a slight re -adjustment of the R.F. compensating condenser may be necessary, as described in
Part II, Section 14.
PILOT
LAMP
UT-227 UY-227
2'2 I. F
0.5 37511
VOLUME
CONTROL
55011
9011
0.5 MFD.
6,000.n. LINK
LINK AND CONNECTIONS
FOR
PHONOGRAPH PICK-UP
(LINK OPEN FOR PICKUP
USE, SEE PART 1, SECA()
Figure 6-Schematic circuit diagram of No. 600 receiver
10