The Hammarlund CB 23 was one of the very first 23 channel crystal synthesized CB radio's on the market. Published here is the text of the rare service manual for this historic rig. Thanks to Dave Earl for supplying the information.

THE HAMMARLUND CB-23
CITIZENS BAND TRANSCEIVER
SERVICE MANUAL
 
CONTENTS OF THE SERVICE MANUAL
Operating Instructions Pages 1 -10 ,
Circuit Description Page 11 .
Service and Maintenance Page 19
Removing and Replacing Chassis Page 19
Replacing Channel Bead Chain Page 21
Alignment Procedure Diagram
Tube Socket Voltages & Resistances Pages 31-32
Parts List
Schematic Diagram 1
Schematic Diagram 2
 
CONTROLS
With the squelch at maximum position, only strong signals will be heard.
Thus, you can cut out unwanted weak (and noisy)
transmissions from distant stations. When turned to the extreme counter-clockwise position,
but not far enough to click the ANL OFF switch (controlled by the same knob), the loud-
speaker will be live at all times and all station's within range will be heard. If turned farther
so that the ANL OFF switch clicks, the Automatic Noise Limiter will be cut out and maximum
sensitivity will be achieved. The optimum position of the SQUELCH knob is the point
where background noise is silenced between incoming transmissions, and the stations you want
to receive can be heard.
 
TRANSMITTING
To transmit, adjust the CB-23 to receive on the desired channel as described above.
Listen to make sure the channel is not in use, hold the microphone not less than three inches
from the lips and, when the channel is clear, press the microphone push button and talk.
That's all there is to it.
As soon as you have transmitted your message, release the microphone push button
so you can hear the reply. The microphone push button converts your transceiver
into a transmitter when it is pressed, and converts the transceiver back into a receiver when
the push button is released.
To transmit and receive on another channel, select the desired channel with
SECTOR knob and CHANNEL knob. Adjust TUNE knob, VOLUME knob and
SQUELCH knob as described above. Before transmitting, by pressing microphone
push button, "listen" to make sure the channel is not in use.
WARNING A valid radio station license is required in order to use the CB-23 as a transmitter. Severe penalties can be imposed if you operate a radio transmitter without a radio
station license. You may not use someone else's license. However, you may use the CB-23
as a receiver only without, or until you get a license.
 
OPERATING PROCEDURES
You and other Citizens Band users will get more satisfaction from the use of your
Citizens Radio if you and they employ proper operating procedures.
 
RECEIVING
Check the operating controls to make certain they are set properly for receiving
on the selected channel. The number of the channel you have selected will appear at
channel indicator window. You may listen on any channel by selecting the desired
channel with SECTOR knob and CHANNEL knob, and adjusting for optimum operation
with the VOLUME, SQUELCH and TUNE knobs. The relative strength of a received
signal is indicated by the meter.
 
TRANSMITTING
The effectiveness of your transmissions depends upon the channel being-clear and
upon the way you use the microphone. Hold the microphone close to the lips. If you hold
it too far away, your transmitter's effective range and loudness will be impaired. Talk in
a normal speaking voice when transmitting, enunciate clearly and don't shout or speak too
softly.
 
INITIATING CALLS
To call a station of another licensee, press the microphone push button and ,
announce your call letters and the call letters of the station you are calling in the following
manner "KRT-794 calling KRO-242". Release the microphone push button and listen
for a reply. When a reply is heard, adjust TUNE knob for best reception.
To call a mobile unit or base station covered by your own station license, announce
your call letters and unit number and the unit number of the station being called in the following manner "KRT-794 Unit One calling Unit Two". Release the microphone push button
and listen for a reply.
 
RESPONDING TO CALLS
When you hear someone calling you, wait until the caller has stopped transmitting.
Then pick up your microphone, press the microphone push button and acknowledge the
 call in the following manner "KRT-794 back to KRO-242, over" . Release the microphone
push button (8) and listen for the message. If the call is from one of your own units reply
like this "KRT-794 Unit One back to Unit Two".
 
CONCLUDING TRANSMISSIONS
Two-way radio communication is maintained by alternately pressing the microphone
push button to transmit and releasing it to listen. At the conclusion of a conversation
announce your station call letters and sign off in the following manner "KRT-794 out" .
 
ON-THE-AIR COURTESY
Since others may want to use the channel on which you are operating, keep all
transmissions as short as possible, make no unnecessary transmissions and don't transmit when
your channel is in use. To avoid loss of your license, or possible fine or imprisonment or
both, by inadvertent or deliberate violation of the law, read and comply with F.C.C. (or
D.O.T. in Canada) regulations. Get a copy of Volume VI, F.C.C. Rules and Regulations,
which contains Part 19, from your CB-23 dealer, a field office of the U.S. Department of
Commerce, or from the U.S. Government Printing Office, Washington 25, D. C.
 
COMMUNICATING RANGE
Intercommunication by Citizens Radio Stations operating in the 26.96-27.23 Mc/s
band are limited by law to 150 miles. This range is seldom achieved. The purpose
of Citizens Radio is to provide short-range personal and business communications facilities .
Communicating distance is determined by "effective antenna elevation", noise, receiver
sensitivity, effective radiated transmitter power and the way you use your microphone .
Range may vary from one mile or so to 20 miles or more, depending upon many factors .
EFFECTIVE ANTENNA ELEVATION, which is not the same as antenna height, is the
"effective elevation" of the antenna above surrounding objects and those intervening in the
radio transmission path. In general, the greater the effective antenna elevation, the greater
the range you will enjoy.
The "height" of your antenna is specifically limited by F.C.C. regulation.
Refer to Volume VI, F.C.C. Rules and Regulations.
 
NOISE
Your CB-23 is a very sensitive receiver. If there were no "noise" to contend
with, your receiving range would be greatly extended. Its receiving range, which cannot
be increased by making the receiver more sensitive, can be extended by reducing noise
pick-up. This can be done by installing the antenna where it will pick up less noise and
more signal, and by suppressing the noises at their source.
Noise generated by the ignition systems of automobiles is the worst offender. It
is a "popping" noise, much of which is eliminated or reduced by the Automatic Noise
Limiter (ANL) built into your CB-23.
Noise is a form of radio signal which is generated by sparking electrical contacts,
such as the brushes and commutator of a sewing machine motor, the vibrating contacts of an
electric shaver, etc .
Information about suppression of ignition interference is contained elsewhere in
this manual. Techniques for locating and suppressing other man made electrical interference
are described in several books on the subject which are available at radio parts stores and
technical book shops.
You can do something about the noise generated by your own automobile or boat
and in your home. But, there is little you can do about noise generated by other cars.
 
VEHICULAR INSTALLATIONS
The CB-23 is designed to be installed under the dashboard of a car or truck by
means of the mounting plate furnished. Since the CB-23 is compact, it can be installed at
any convenient location.
Under dash Mount
Using the mounting bracket as a template, find the best location under the dash
of the vehicle, taking into consideration handles, controls and the glove compartment.
Bolt the mounting frame securely in place. Find a convenient location for the microphone
mounting clip and fasten it securely, taking into consideration that the microphone cord ,
might hamper the driver if the microphone mounting clip is not correctly placed.
Power Cable
Route the DC power cable so that its leads will reach the power take off point.
This can be at the ignition key I the ammeter or the storage battery, the red lead secured
to the ungrounded line and the black lead secured to the vehicle frame. The best way is
to connect the red lead directly to the ungrounded battery terminal and the black lead to
the grounded battery terminal.
Antenna
You have a wide choice of mobile antennas. Install your antenna and connect
the antenna end of the coaxial cable as instructed in the directions furnished with the
antenna. Make sure the ground contact of the antenna base makes excellent contact with
the car body. If you use a bumper mount, ground the bumper to the car frame with a short
piece of flat metal braid .
Route the coaxial cable to the CB-23 location. The set end of the coaxial.
cable must be terminated in a PL-259 UHF connector .
Attach the antenna plug to the antenna receptacle at the back of the CB-23,
and insert the coaxial socket at the set end of the DC power cable into the octal power
connector, also at the back of the CB-23. Turn VOLUME knob clockwise. The pilot
lamp behind the channel number window should now light. If your power take off
point is at the ignition switch, turn the ignition switch on if the pilot lamp doesn't glow.
After a minute or so, you should be able to hear CB stations by setting the
CB-23 to various channels. You are now ready to receive and transmit (if you have a
license).
Antenna Tune-Up
Your CB-23 has been adjusted for optimum output into a 50 ohm dummy antenna at
Channel 12. Since channel 12 is approximately the center of the range of the 23 channels, it
is suggested that all antenna tune-up adjustments be made on this channel. This is especially
true if all 23 channels are to be utilized. The antenna tune-up procedure, which follows,
should only be employed to check the antenna system or when it is desirable to favor one
particular channel or group of channels or in the event that an antenna system deviating
from 50 ohms impedance is employed. In all cases, it is advisable not to make the antenna
tune up adjustment unless you are experienced and have the necessary equipment to do this
job properly.
To get maximum capability from your transmitter you should tune your CB-23 to
the antenna system. To do so, you need a field strength meter {Lafayette TM-14, Monarch
FS-1) or a thru-Iine type RF power meter (Seco 520, Cesco CB-52C, Lafayette TM-58).
If you use a field strength meter, place it a few feet from the antenna, but where
you can see it. Turn the CB-23 on its side to expose the two alignment holes in the bottom.
Set the CB-23 to Channel 12 and insert the tuning tool (General Cement Co., No.8606) into
hole A (see diagram) so that the tool engages the core of the transmitter tank coil {Ll06).
When the channel is clear, press the microphone push button and turn the core for maximum field strength meter reading. Release the microphone push button and insert an
insulated screw driver in hole B so that it engages with the screw of the antenna trimmer
(C152). Press the microphone push button when the channel is clear, and turn the screw
for maximum reading on the field strength meter. Release the microphone push button
and re-insert the special tuning tool into hole A. When the channel is clear, again press
the microphone push button and readjust the core (L106) for maximum field strength
meter reading.
If you use a thru-Iine RF power meter, disconnect the antenna plug from the
CB-23 and connect it to the output receptacle of the RF power meter. Using a coaxial
jumper (with plugs at both ends), connect the input terminal of the RF power meter to the
CB-23 antenna receptacle. Set the RF power meter switch to measure "power output" or
"incident power". Tune L106 and C152 as described in the above paragraph for maximum
meter reading . Set the RF power meter to measure "reflected" power. Retune L 106 and
C152, if necessary, until there is a maximum difference between "reflected" (low reading)
and "incident" (high reading) meter indications.
Whenever making these adjustments, announce the station call letters at the
beginning and end of a series of test transmissions .
If you do not have a field strength meter or RF power meter, have the antenna
tune up performed by a competent technician .
 
Boat Installations
Fasten the mounting plate, furnished with your CB-23, at a convenient location,
preferably at a distance from the engine to reduce ignition noise pick up. Route the DC
power cable, extending it, if necessary, to the boat's battery. The battery must be a
12 volt lead acid type storage battery. If it is an Edison battery, measure the voltage
across it while the engine is running. The voltage must not exceed 14.5 volts.
On a non-metallic boat, a coaxial antenna will probably be most effective since
it is like a mast (18 feet tall) and has no horizontal ground radials. You can use a base
loaded whip or a full-length {9-foot) whip if you also install a ground plane (sheet metal or
screening) at the base of the antenna. Connect one end of the coaxial cable to the antenna
as instructed in the directions furnished with the antenna .
The other end of the coaxial cable must be terminated in a PL-259 UHF connector which is inserted in the SO-239 antenna connector at the rear of your CB-23.
When the antenna and power connectors have been properly connected to your
CB-23, turn VOLUME knob clockwise. The channel indicator window should be
illuminated. After a minute or so, you should be able to hear CB stations on one or more
channels. You are now ready to receive and transmit (if you have received your license).
To get maximum transmission capability, tune the CB-23 to the antenna as described under ANTENNA TUNE UP, or have this done for you by a competent technician.
 
FIXED INSTALLATIONS
To use the CB-23 at a fixed location, you must also have a suitable antenna
system and a source of electric power at 115 volts (nominal}, 60 cycle AC or 12 volts DC
(where utility power is not available). To operate the CB-23 from a 220 volt AC source,
an external step-down transformer is required. Where only 24, 32, 36 or 110 volt DC
power is available, a suitable DC to AC inverter is required.
Insert the octal socket of the AC power cable into the octal plug at the rear of
the CB-23 and the two-prong plug at the other end of the cable into an AC outlet. If .
operation from a 12 volt DC source is required, use the DC power cable and connect its
leads to the battery of other DC source. Turn VOLUME knob clockwise. The pilot lamp
behind the channel number window should glow.
The antenna may be one of the many types now available which are designed to
operate in the 27mc band and to be fed through a 50 ohm coaxial cable. Install the
antenna, and connect the coaxial cable to the antenna as instructed in the directions
furnished with the antenna .
The other end of the coaxial cable must be terminated in a PL 259 UHF connector in order to mate with the S0 239 connector at the rear of your CB-23. If you have
had no experience with attaching a connector to coaxial cable, have this work performed
by a competent technician, or buy a piece of coaxial cable of sufficient length which is
already equipped with a PL 259 connector.
Never splice coaxial cable. If the coaxial cable is only a few feet longer than
required, don't cut it, instead use it as it is, the excess coiled up if necessary. For runs of
less than 50 feet, you can use RG-58/U coaxial cable. Better, for any length requirement
is the lower loss RG-8/U coaxial cable, Foamflex, balloon or other type of low loss
coaxial cable of 50 ohm impedance. If you are not technically qualified to select coaxial
cable, consult your CB-23 dealer.
To provide lightning protection, consult your CB-23 dealer about a coaxial-type
lightning arrester and install it as instructed. Or, ground the antenna support pipe or bracket
through a straight as possible length of No.12 or larger wire to a cold water pipe or ground
rod driven into moist earth, using a ground clamp to make a secure ground connection. Or
connect a flexible wire from one of the screws at the back of your CB-23 to a cold water
pipe or ground rod .
After you have connected your CB-23 to the antenna system and to a suitable
power source, you are ready to use the CB-23 as a receiver. If you have a station license,
or when you receive it, you are ready to transmit. To get maximum capability from your
transmitter, tune the transmitter to your antenna system, as described under Antenna Tune
Up, or have a competent technician do it for you.
 
IGNITION NOISE SUPPRESSION
You can do something about noise generated by your own car, truck or boat, but
you cannot do anything about stopping the radiation of noise generated by other nearby vehicles.
The typical modern automobile is equipped at the factory for suppression of noise
that will interfere with the operation of AM broadcast band receivers. But, this treatment
may not be adequate for Citizens Band reception .
Noise suppression kits are made by several manufacturers (SPRAGUE , HALLETT,
ESTES, GC ELECTRONICS) which are designed specifically for suppressing noise at
Citizens Band frequencies.
To determine if your car, truck or boat is the source of noise, turn on your
CB-23 and turn SQUELCH knob fully counter clockwise (beyond the click). Listen to the
background noise with the engine off. Then start the engine and listen for an increase in
noise. Vary the speed of the engine. If there is a change in the rate at which the popping
noise occurs, your engine is the culprit. If you hear a whining noise, which changes in
pitch as you accelerate the engine, it is again your engine that is at fault.
It would require an entire book of this size to explain the how, why and what to
do of noise problems. If you are plagued with this problem, you can get informative advice
from a booklet entitled "Giving Two-Way Radio Its Voice" which is available from Automotive
Technical Service Dept., Champion Spark Plug Co. Inc., Toledo 1, Ohio.
The CB-23 was designed for long life and to give reliable service. It contains
many resistors, capacitors and other components which were carefully selected by the
manufacturer. Even so, a component in any piece of electronic equipment may fail or
change in characteristics, necessitating replacement. The tubes, vibrator and pilot lamp
can wear out and may require periodic replacement. These can be replaced by the user,
if he wishes to do so, preferably by a competent technician.
 
TUBES
You can test the tubes yourself if you have a tube tester, or with a do-it-yourself
 tube tester in a neighborhood store, or by taking the tubes to a radio shop for testing.
Replace all weak, shorted or burned out tubes with new tubes of identical type. When you
remove the tubes for testing, note which tube belongs in which socket. Sometimes, a tube
which checks OK on a tube tester may not function properly in your set because all tube
testers are not sufficiently critical.
 
VIBRATOR
The vibrator, which is active only when you operate your CB-23 on a 12 volt
battery, is a plug-in device similar in appearance to a metal can. To replace it, pull the
vibrator out of its socket and install a new one of identical type. If replacement of defective tubes and the vibrator does not restore operation, re-install the original vibrator
and have your CB-23 checked by a competent technician.
NOTE: If your CB-23 should be totally inoperative, or if smoke or a burning odor is
noticed, turn it off immediately and have it checked by a competent technician. Continued
operation under such circumstances can cause additional damage.
WARNING .
Certain repairs and adjustments to the CB-23 may be made legally only by a
person, or working under the direct supervision of a person, possessing a valid First Class
or Second Class F.C.C. Radiotelephone Operator License (or equivalent in Canada).
This particularly pertains to those repairs or adjustments, such as replacement of crystals
and transmitter oscillator components, which might affect the transmitter's ability to comply
with government regulations.
The CB-23 may not be operated as a transmitter except when covered by a valid
Class D Citizens Radio Station license in the United States or a General Radio Service
license in Canada. Any U. S. citizen (in Canada a landed immigrant is eligible) over
18 years of age may apply for such a radio station license .
The license application consists of F.C.C. form 505, which when completed,
must be submitted to the Federal Communications Commission. These forms are available
from your CB-23 dealer, your nearest F.C.C. field office or the Federal Communications
Commissions, Washington 25, D.C. Instructions for completing the license application
are furnished with the forms.
 
After you have filed your license application, you may have to wait several
weeks for your license. But, you may not legally operate your transmitter until after your
license has been granted and is in your possession.
 
Antenna Tune-Up
Your CB-23 has been adjusted for optimum output into a 50 ohm dummy antenna at
Channel 12. Since channel 12 is approximately the center of the range of the 23 channels, it
is suggested that all antenna tune up adjustments be made on this channel. This is especially
true if all 23 channels are to be utilized. The antenna tune up procedure, which follows,
should only be employed to check the antenna system or when it is desirable to favor one
particular channel or group of channels or in the event that an antenna system deviating
from 50 ohms impedance is employed. In all cases, it is advisable not to make the
antenna tune-up adjustment unless you are experienced and have the necessary equipment
to do this job properly.
C B - 23 Circuit Description
Many transmitter or receiver troubles can frequently be resolved simply by
testing and changing tubes and by making a few minor adjustments, but in order to
properly service this set, it is important to be able to diagnose obscure troubles through
an understanding of the circuits involved. It is for this purpose that this section is
provided. A transceiver of this type contains several special circuits that are not usual
in the normal transmitter or receiver commonly available. While not difficult to under-
stand or service, the best operation is obtained when the set is adjusted in accordance
with these instructions.
The complete circuit of the CB-23 is shown in the schematic diagram included
at the end of this book. To help in .understanding this diagram, a block version is presented on the next page. While reading the text, follow both the block and schematic
diagrams, one will illustrate the overall scheme, while the other will provide all of
the connection details.
 
RECEIVER GENERAL CIRCUITRY
The receiver is a sensitive double superheterodyne using a crystal controlled
first oscillator , and a temperature compensated second oscillator that is capable of
sufficient front panel tuning control to compensate for slight frequency differences of
received transmissions. A diode detector, an automatic noise limiter and an adjustable
squelch system are included, and an efficient audio amplifier circuit provides ample
power for the self-contained loudspeaker.
The received signal is applied to the RF stage through the transmit-receive
relay contacts. Frequency conversion occurs in the first mixer to produce the first
intermediate frequency (IF). The second mixer follows to produce the second IF. The
second IF amplifier applies 262 KCs to the detector for the development of the audio
signal.
The recovered audio is then applied to the noise limiter and squelch circuits
as shown In the accompanying detailed diagram of this area. Assuming the squelch
control turned fully counterclockwise and the ANL off, the audio is applied through
the squelch tube to the volume control. The squelch tube is conducting at this time
because V105 is conducting and clamps the grid and cathode return of V107 providing
normal bias.
The automatic noise limiter is activated when the switch S104 is opened by
turning the squelch control clockwise past the switch. The diode now opens the audio
path when high noise signals such as ignition or similar pulse types are received. This
audio discontinuity is momentary and does not effect intelligibility of the signal. Note
that only the elimination of such noise at its source will provide the complete answer to
ignition noise problems.
Turning the squelch control clockwise applies a positive voltage to the
cathode of the squelch tube. This voltage results in a high negative bias applied
to the grid, effectively cutting off conduction. When no signal is being received, no
audio in the form of set or atmospheric noise is permitted to pass. When a signal is
received, the signal produced counteracts the squelch control voltage until the cathode
and grid returns are clamped and conduction occurs. The received audio is then passed
to the volume control. From the above it is seen that the signal produced must be great
enough to overcome the squelch control voltage. For this reason the correct setting of
the squelch control is to turn it clockwise with no signal being received, until the back-
ground noise just disappears. Now when a signal is received, the squelch is overcome,
and audio is heard.
A conventional audio amplifying circuit, consisting of V107A and B applies
audio to the loudspeaker. The carrier level meter is in a bridge arrangement and is
balanced between the cathode voltage of the second IF tube and the cathode voltage
of the audio output tube. With no signal received the meter is set to zero by R128.
When a signal is received, AVC is produced, and the second IF is biased to reduce
plate current, unbalancing the meter circuit to cause the meter to read. The AVC
is proportional to the strength of the received signal so that the meter reading will
increase accordingly.
 
TRANSMITTER GENERAL CIRCUITRY
When the microphone button is depressed, the transmit-receive relay operates
to mute the receiver and to turn on the transmitter. This occurs through the removal of
B+ from the screens of the receiver RF and second mixer stages, transferring it to the
transmitter oscillator and driver.
Transmitter modulation is developed by applying the microphone audio through
the microphone amplifier and the audio output stage of VI07B. The audio output trans-
former TI07 acts in this case as the modulation transformer to produce plate modulation
of the transmitter power output tube. The resulting modulated RF is applied to the antenna through. the contacts of the transmit-receive relay. Antenna loading and tuning
are accomplished by the adjustments of Ll06 and CI52.
 
CHANNEL CRYSTAL SELECTION SYSTEM (Refer to Channel-Frequency Chart.)
While the receiver and transmitter electronic circuits are quite straight forward,
the crystal oscillator arrangements to cover all 23 channels using a minimum of crystals is
novel. This system is shown on the diagram, and the list of frequencies illustrates the
method of obtaining the final IF for the receiver, and the RF output for the transmitter.
The design of the receiver, using crystals, is made possible by the fact that
the spacing between channels is repeated in groups of four: 10 KCs spacing between
channels 1and 2, and between channels 2 and 3; 20 KCs spacing between channels
3 and 4. This pattern is repeated up to channel 23 except that the 23rd frequency is
omitted and the 24th is numbered channel 23. For the best design results, the CB-23
includes 8 crystals for the first 8 channels then reuses them, in order, for the remaining
two 8-channel groups.
An inspection of the frequencies of channels 1, 9 and 17 will show that they
are l00 KCs apart in turn. The heterodyne between each of the channel frequencies,
produces three different intermediate frequencies in turn, each 100 KCs apart. In the
receiver, the tuned circuits between the first and second mixers are switched to tune to
the proper intermediate frequency as required.
Since there are three first intermediate frequencies, the second oscillator is
also adjusted in frequency to produce the final I F of 262 KCs for all channels received.
The technique designed to obtain three intermediate frequencies in the receiver
is reversed to produce the RF output for the transmitter .Now the receiver first oscillator
frequency is heterodyned with three transmitter oscillator frequencies to produce all of the
channel frequencies. The receiver first mixer is used for this frequency heterodyning process, and the final channel signal is applied to the transmitter driver through the top sections of the interstage coils T102 and T107.
Finally, switch sections are reserved to permit channels to be inactivated for
transmission. These are: S101A, sections 2,3 and 4; S101B, all sections; S101C,
section 4; S102A all sections. The wiring provided with the CB-23 does not permit the
frequency between channel 22 and 23 to be transmitted. In the same manner, it is possible to prevent any other channel or channels from transmitting. This wiring does
not affect the receiver; all channels can be received. The switch wiring system is
shown in the illustration.
 
POWER SUPPLY SECTION
The cables supplied permit the use of the CB-23 from either 115 volt AC 60
cycle, or a 12 volt DC source. In either case the secondary of the power transformer
feeds a voltage doubler circuit using two diode rectifiers.
 
CB-23 SERVICE AND MAINTENANCE
 
REMOVING AND REPLACING THE CHASSIS
Disconnect the antenna and the power cables, remove the screws from the
bottom of the cabinet, and pullout the chassis.
When replacing the chassis, line up the holes in the cabinet with the chassis
points designed to receive the screws.
 
REPLACING THE CHANNEL DIAL DRIVE BEAD CHAIN
Normally it should not be necessary to remove the front panel except to repair a
part of the channel or sector indicator dials or dial drives. The instructions below show
how the panel is to be removed, and provide the proper method to replace the channel
dial drive bead chain. Refer to the diagrams for the location and identification of all
parts.
Step 1. Remove the chassis from the cabinet .
Step 2. Remove the five knobs from the controls. The tune knob is held by a set
screw, the others just pull off.
Step 3. Set the tune control so that its plates are fully meshed. Remove the nuts
holding the headphone jack and the tune control.
Step 4. At the rear of the panel remove the two nuts holding the meter wire lugs.
Be careful not to turn the nuts against the meter back these are internal
mounting points.
Step 5. Remove the three screws and nuts holding the panel to the chassis. Note that
two of the stand offs will be loose but the third holds the microphone cable clamp.
Step 6. Turn the panel around towards the microphone cable to expose the dials.
Step 7. Loosen but do not remove the two set screws holding the sector plate to its
control shaft. Pull off the plate .
At this point you are ready to replace the bead chain. Because the chain must fit over the
pulley on the dial shaft behind the dial, the dial and pulley must be removed. While
removing the dial by loosening the pulley set screws may be a simple method, it is
recommended that the C-washer be removed, and the dial and shaft be pulled out.
This retains the dial positioning on its shaft.
The bead chain is intended to fit tightly. If difficulty is found in inserting the shaft into
the bushing when the chain is in place, loosen the bushing nut sufficiently to tilt the
bushing. Now the shaft will be inserted easily. CHECK THAT THE DIAL INDICATION
AGREES WITH THE CHANNEL SWITCH POSITION. See illustration. Tighten the
bushing nut, using two wrenches if necessary. Replace the C washer.
Reverse the steps above to replace the sector dial, the panel, the knobs, etc. Follow the
illustrations for the proper locations of all parts. Position the sector dial plate so that the
open spaces expose the numbers properly.
 
ALIGNMENT PROCEDURE
The CB-23 has been carefully aligned at the factory and should not require any
more than a slight adjustment to retain the peak of its performance. If alignment is
necessary, follow the instructions provided below with care.
For the alignment procedure, the equipment listed below is required:
Thin shaft insulated screwdriver.
Non metallic alignment tool. (General Cement Co., No. 8606)
DC vacuum-tube voltmeter.
Signal generator(s) capable of accurately producing unmodulated
signals of: 262 KCs, 1650 KCs, 1850 KCs, 27.1 MCs.
Field strength meter (Lafayette TM-14 or Monarch FS-1) or
through-line type power meter for RF (Lafayette TM-58,
Seco 520 or Cesco C B-52C )
Alignment must be undertaken with the CB-23 chassis out of its cabinet. Remove
the chassis from the cabinet as instructed in this Manual. (Service and Maintenance
Page 19.)
Connect the CB-23 line cord into the correct source of power and turn it on.
BEFORE ALIGNMENT, THE SET MUST BE ALLOWED TO WARM UP FOR AT LEAST A
HALF HOUR. This is to assure frequency stability.
After warm up, check that no signal is being received and adjust the meter zero
control on the right side of the chassis for zero on the meter scale, if required.
Turn squelch control off. Set the tune control so that the plates are in half
mesh (dot on knob In line with dot on panel).
Note that the coil slugs are adjusted from the top of the can. Be sure you are
turning the correct slug when there are two slugs in the same can it is easy to be
turning the wrong one, or even to be turning both at once if they happen to be close
together inside the coil.
Receiver
Step 1. First Oscillator -The common connection of the RF amplifier and the first
oscillator feed at the grid of V102A can cause interaction in the tuning of L102 and L103,
resulting in feedback that sounds as a loud burbling noise in the loudspeaker. Follow
these instructions to be sure of correct tuning without feedback.
Connect the VTVM between Pin 9 of V102 and ground as shown in the diagram.
Turn the slug of L102 counterclockwise as far as possible. Turn the slug of L103 counter-
clockwise as far as possible.
Now turn the slug of L103 slowly clockwise until the VTVM shows 20 volts DC.
This is the correct tuning point. Note that if the slug is continued to be turned clockwise,
the voltage will continue to rise and then fall off until oscillation finally stops. Be sure
you have tuned L103 as directed above for correct operation.
Step 2. Second IF -Connect the VTVM between the pin of T103 and ground as
shown in the diagram. This connection will remain for all of the receiver alignment
procedure to follow.
Apply an unmodulated 262 KCs signal to pin 7 of V103 as shown in the diagram.
Adjust both slugs of T103 and T104 for a peak reading. Set the input signal level so that
the VTVM reads between -1 and -1.5 volts when the coils are peaked. Repeat these
adjustments until no further improvement can be noticed.
Step 3. Second Oscillator -Set the sector switch extreme clockwise, to the highest
sector. Apply an unmodulated 1850 KCs signal in place of the 262 KCs signal of Step 2
as shown in the diagram. Adjust L104 for a peak negative reading of the VTVM. Remember
to reduce the input signal level as necessary to maintain about -1 to -1.5 volts.
Step 4. First IF -Set the sector switch counterclockwise, to the lowest sector.
Apply an unmodulated 1650 KCs signal to pin 6 of V102 as shown in the diagram. Adjust
the TOP slugs of T102 and T107 for a peak reading on VTVM, maintaining -1 to -1.5
volts as in Step 3.
Step 5. RF and Mixer -Set the sector and channel switches to receive channel 12.
Apply an unmodulated 27.1 MCs signal to the antenna input connector J101. Adjust
L102 and T101 for a peak reading, again maintaining -1 to -1.5 volts as in step 3 and 4.
Transmitter
Connect the transmitter RF output to an RF power meter and 50 ohm dummy load. To
activate the transmitter for these adjustments, press the microphone switch.
Step 6. Mixer and Driver -Set the sector and channel switches to receive channel
12. Connect the RF output into a 50-ohm dummy load. Connect the VTVM between the
pin of L108 and ground as shown in the diagram. Adjust the BOTTOM slugs of T102 and
T107, and L108 for peak VTVM reading. Check for proper adjustment by shorting crystal
Y102 (see diagram for location). If the adjustments were correct, the meter reading
should drop to zero.
Step 7. RF Output -Set up the field strength meter or the thru-line RF power meter
measure the output of the transmitter. Set the sector and channel switches as above to
channel 12.
Using the RF thru-line meter: Set the meter to read Power Output of Incident Power.
Adjust L106 for a peak RF thru-line meter reading. Now adjust C152 for a peak reading
and repeak L106 again. Continue alternate tuning of C152 and L106 until no further
improvement can be noted on R.F. thru-line meter.
This completes the entire alignment procedure for the transceiver. Return the
chassis to the cabinet, reconnect the antenna and power cables, ready for operational
use.
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