REL 518-D User manual

INSTRUCTION MANUAL
FOR
MODEL 518(D)-DL
ONE THOUSAND WATT
FREQUENCY MODULATED
BROADCAST TRANSMITTING
EQUIPMENT
RADIO
ENGINEERING
LABORATORIES

INSTRUCTION MANUAL
FOR
MODEL 518(D)-DL
ONE THOUSAND WATT
FREQUENCY MODULATED
BROADCAST TRANSMITTING
EQUIPMENT

TABLE OF CONTENTS
MODEL 518 INSTRUCTION MANUAL
SECTION I. INSPECTION OF RECEIVED MATERIAL - CLAIMS FOR BREAKAGE IN SHIP-
MENT
SECTION II. GENERAL DESCRIPTION OF EQUIPMENT
SECTION III. ASSEMBLY AND INSTALLATION
SECTION IV. THEORY OF OPERATION
SECTION V. PRELIMINARY ADJUSTMENTS AND OPERATION OF THE EQUIPMENT
SECTION VI. MODULATOR AND POWER AMPLIFIER ADJUSTMENTS
SECTION VII. CONSOLIDATED PARTS LISTS
SECTION VIII. MAINTENTANCE OF EQUIPMENT - ORDERING SPARE OR REPLACEMENT PARTS
PROCEDURE FOR RETURN OF MATERIAL
ACCESSORY DATA SUPPLIED 'dITH THIS MANUAL IN REAR COVER POCKET: -
6 COPIES DEFECTIVE MATERIAL NOTIFICATION FORM
6 COPIES DEFECTIVE MATERIAL RETURN FORM
IN SEPARATE DRAWING FOLDERs-
TITLE NUMBER
INSTALLATION DRAWING T-68
STATION WIRING DIAGRAM B-654
MODEL 518 WIRING DIAGRAM SS-635
CONTROL CIRCUITS - ACROSS THE LINE DIAGRAM B-629
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SECTION 1
INSPECTION OF RECEIVED MATERIAL
RE-ASSEMBLY OF PARTS REMOVED FOR
SHIPMENT - CLAIMS FOR BREAKAGE
IN SHIPMENT.
1. UISPECTION OF RECEIVED MATERIAL
Received material should be carefully inspected at the time of uncrating for
evidence of damage or breaking due to careless handling in transit. Care and good
sense should be used in the process of unpacking or uncrating the equipment. Hasty
use of improper tools such as crowbars, etc., may easily result in damage to the
enclosed equipment. Be sure to note and follow externally marked instructions such
as, "This End up" or "Oper. This End ", etc. All equipment is carefully packed at
the factory to insure safe delivery with reasonably careful handling. When remov-
ing items from packing material check item by item against the enclosed pecking
list for errors or short shipment.
2. CLAIMS FOR BREAKAGE IN SHIPMENT
In cases of damage to equipment due to faulty handling in shipment, notify car-
rier immediately leaving broken or damaged item or items exactly as found in pack-
age. Do not destroy or remove any of the wrappings or protective material involved
in the wrapping of the damaged item. Carrier companies will not accept claims for
"Damage in Shipment" unless they can inspect the damaged item and its associated
packing material. Claims must usually be made within five days of receipt of ship-
ment.
Section 1 - 1

SECTION II
GENERAL DESCRIPTION OF EQUIPMENT
A. General Description
The REL Model 518 FM Broadcast Transmitter is designed to deliver 1000 watts
of radio frequency power at any selected frequency from 88 to 108 megacycles. Modu..
lation is accomplished by the Armstrong Dual Channel Phase Shift method, the modula-
tor being an integral part of the transmitter.
The equipment is completely housed in a vertical steel cabinet normally finished
in two tone green lacquer with chrome trim. The cabinet is 84" high, 40" wide and 36"
deep.
Various functional units in the equipment have been sectionalized on individual
chassis. Each separate chassis is hinged at one end and may be swung out for conven-
ient inspection or maintenance work.
B. Primary Power Connections
Refer to drawing B-654 which shows details of the transmitter input terminal
boards and connections.
208/230 volts, 60 cycles single phase should be terminated at the terminals mark-
ed A, B, using #10 AWG wire or larger. Primary load for rated output is approximately
3700 volt amperes at 890 power factor. 110 to 120 volts single phase should be connect-
ed to terminals 3 and 54 using #12 AWG wires for powering the convenience outlet
and interior lighting.
A good low resistance ground should be connected to the terminal marked "0" on the
terminal board which is located on the left vertical frame member just inside the lower
front panel.
C. Output Transmission Line Connections
The equipment is supplied for operation with a single 7/8" coaxial transmission
line which enters the top of the cabinet. Location of this point may be determined by
reference to outline drawing T-68.
D. Accessory Data
A 600 ohm balanced audio input line must be connected to the twin conductor jack,
which is located behind the lower front panel on the right hand corner post. This line
should be of the insulated shielded twisted pair type and should avoid proximity to high
level AC lines. Since there is not pre-emphasis included in the transmitter standard 75
micro second pre-emphasis should be included at some point in the audio equipment.
A coaxial jack is provided beside the audio input jack for connecting the monitor
to the sampling loop in the power amplifier cabinet.
Section II - 1

SECTION III
ASSEMBLY AND INSTALLATION
A. After the equipment has been unpacked remove all panels to permit easy access
to the interior. A considerable amount of packing material shipping straps and
braces will be found within the equipment, notably in the high voltage supply re-
lay panel, modulator power supply, and power amplifier compartment. This material
should all be removed and the supported parts carefully examined for any damage
which may have occured while the equipment was in transit.
B. After the equipment has been located in its final position the power lines may
be connected. Provision has been made in the cabinet design to permit cable en-
trance either through exposed conduit or concealed floor trench type wiring. A "TEE"
shaped duct is built into the base of the transmitter which allows conduit entrance
via either side near the front or through the rear center. The location of these
knockouts is indicated on the installation drawing T-68. In addition an 8" x 2" open-
ing covered with a removable plate is provided for entrance of cables via a floor
trench. If used, this palte should be removed and holes cut to permit passage of the
cables. Unless the plate is reinstalled, an air leak will result, thus destroying
the effectiveness of the intake air filter.
Primary power connections are made to terminals "A" and "B ". The auxiliary
lighting circuit connections are connected to terminals 53 and 54.
C. The output transmission line connections may now be made up.
D. Connect the audio input line and the monitor by means of the plugs which are pro-
vided in their respected jacks.
E. Install plug in resistors which are located as noted below:
SYMBOL NO. STOCK NO. RESISTANCE LOCATION
R-800 R-5104 or R-5273 200,000 ohms Resistor panel left side, bottom
row, center.
R-801 R-5105 5 neghom Resistor panel, bottom row, rear.
R-803 R-5097 or R-5269 500 ohms Resistor panel, bottom row, front.
R-805 R-5109 or R-5271 250 ohms Resistor panel, middle row.
R-806 Same as R-805 Resistor panel, middle row.
R-807 R-5321 500 ohms Bottom of grid circuit.
R-808 Same as R-805 Resistor panel, middle row.
R-809 Same as R-805 Resistor panel, middle row.
R-810 R-5321 500 ohms Below PA tube deck, left.
H--811 R-5269 500 ohms Resistor board, lower right side.
R-812 Same as R,-811 Resistor board, lower right side.
R-818 R-5336 1250 ohms Resistor panel, left side, top row,
rear.
R-819 B-5337 2000 ohms Resistor panel, left side, top row,
front.
R-820 R-5321 500 ohms Below PA tube deck, right.
Section III - 1

F. Install all tubes. Pilot lights and glass fuses are shipped in their res-
-oective sockets.
G. There are five lumiline lamas to be installed. Two are used to illuminate
the meter panel and the sockets for these will be found directly below the meters.
Two are used inside the power amplifier compartment and operate when the compart-
ment door is opened. One is located inside the plate compartment on the top front
Hanel. The other is located under the PA tube deck just inside the front flange.
The fifth light is located on the rear of the same cornerpost which supports the
audio input jack.
Section III - 2

SECTION IV
THEORY OF OPERATION
A. POWER CONTROL CIRDUIT
1. General
The power controls are designed to provide either complete manual or semi-
automatic control with facilities provided for remote control of the application
of power to the various stages, proper protection of equipment in the case of over-
loads, and reasonable time delays between the application of filament and plate volt-
ages. All cabinet doors with the exception of those over the modulator compartment
and the main front doors, are interlocked for the protection of personnel.
2. Primary Power Source
The main operating power is completely supplied by a 208/230 volt (plus or minus
5%) 60 cycles, single phase source. All filament transformer primary voltages are con-
trolled by the variable auto transformer YR-800 which is located on the right hand con-
trol panel, and should be adjusted to Produce a reading of 5.0 volts on the front panel
"FILAMENT VOLTAGE".
3. Control Circuits
The schematic diagram of the control circuits is shown on drawing SS-638. A func-
tional across the line diagram is shown on drawing B-629 which will be useful in under-
standing the sequence of control operation.
The STANDBY switch 5808 should always be on, except for maintenance work on the
standby circuit. Even so, the input side of 5808 and the main circuit breaker, K800,
will be energized, hence it is advisable to open the main safety switch which powers
the entire transmitter when maintenance work is required. When 5808 is closed, trans-
former T703 is energized through fuse F806 and protective resistor R-715. The second-
ary of T703 operates the crystal heater when the transmitter is off the air. The stand-
by fuses 7807 and F808 provide protection for the standby and blower shut down circuits.
With all of the switches except the STANDBY SWITCH S808 open, the first switch to
be closed is the PRIMARY POWER circuit breaker K800. The coil of the blower relay K806A
is energized through the standby fuses F807 and F808 closing contacts K806B, K806C, and
K806D. The blower time delay relay K807 is also energized through the normally closed
contact K801C of the time delay relay K801. However relay K807 will not operate at this
time since its normal time delay is 2 minutes, and contact K8010 will open 60 seconds
after switch 5800 is closed. Contacts K8060 and K806D apply power to the blower B800
through the thermal eliment K806E, and also to the blower pilot light, I803. The meter
lights 1805 and I806 should come on when K800 is closed.
When the FILAMENT switch 5800 is closed and the blower B800 has reached its Proper
speed, the air switch 5807 will be closed thus energizing the filament variable auto trans_
former YR800 which in turn controls the voltage on T700 through F801 which supplies 6.5
volts AC for the modulator AC filaments; T701 through F802 which supplies 6.6 volts DC
for the modulator DC filaments; K700 which switches the crystal heater from 6.0 volts AC
standby to 6.6 volts DC operate; T800 through F803 which controls the screen the bias
supply filaments; T801 supplying the power amplifier filaments at 5 volts which is read
on the FILAMENT VOLTAGE meter; T804, T805 and T806 which supply the high voltage rectifier
filaments; K801 the rectifier tube time delay (60 seconds) which withholds application of
high voltage until the rectifier tube cathodes are hot and finally I800, the filament
pilot light.
Section IV - 1

60 seconds after the closing of the FILAMENT switch S800, the time delay relay
K801 will operate, closing contact K801B and opening contact K8010. If all door inter-
locks are closed and the MODULATOR HIGH VOLTAGE switch is closed, then the coil of re-
lay K802A will be energized closing contacts K802B and K8020. K802B, when closed, applies
power to the modulator high voltage transformer T702 and the modulator high voltage pilot
light I801, through fuse F804. K802C when closed energizes the high voltage recycling
time delay (5 seconds) through the overload relay contact K805B, and the bias high volt-
age transformer T802 through fuse F805.
After 5 seconds from the time the MODULATOR HIGH VOLTAGE switch S801 was closed
time delay relay K803 will operate, closing its contact, K803B. Then if the HIGH VOLT-
AGE switch S805 is closed, the PA high voltage relay K804 will be energized, closing con-
tacts K804B and K8040 through which power will be applied to the primary of the high volt-
age transformer T803 through the tap changing switch S818, and to the high voltage pilot
light I802. The closing of the power amplifier high voltage switch completes the cycle
of manual operation and the equipment is ready for transmission provided that the eouip-
ment has been previously adjusted for proper voltages and the tuning controls were pro-
perly set. The switching controls are designed so as to control the cycle of operation
at any stage desired. If any of the control switches S-800, S-801 or S-805 are opened,
the cycle of operation will automatically continue to the stage controlled by the particu,
lar switch that is opened and then stop. Further continuation of the operating cycle re-
quires the closing of the switch or switches that follow.
The manual "OFF" operation is performed in the reverse sequence of the "ON" operation,
the power amplifier HIGH VOLTAGE SWITCH S-805 is turned off which removes the power ampli-
fier high voltage then the modulator high voltage switch S-801 is turned off, followed by
the turning off of the filament power switch S-800 and finally the primary power circuit
breaker, K-800.
If for any reason, by manual "OFF" operation or by a heavy overload, the overload
breaker K -800 is opened, only one of the parallel sources of supply for the blower relay
coil L-806A is removed and contacts K-8060 and K-806D remain closed. The power supplied
through these contacts will keep the blower B-800 operating. At the same time that the
circuit breaker K-800 is opened, power is removed from relay coil K-801A, thus closing
contacts L-8010. Contact K-8010 energizes the blower time delay relay K-807, and after 2
minutes, the normally closed contact K-807B opens thus removing the second of the two
parallel sources of power for relay K-806A. This relay opens contact K-806B which turns
off the blower B-800 and the blower pilot light I -803.
Section IV - 2

CAUTION
The standby crystal heater switch S-808 should never be turned off until the
blower B-800 has stopped.
Assuming that S -808 is "on" in the standby position, semi-automatic operation
of the control circuit is obtained by turning on all switches (S-800, S-801, S-805)
except the main PRIMARY POWER circuit breaker K-800. Then when K-800 is closed, the
relays function as previously described and after approximately 65 seconds, the
equipment is ready for transmission. The "stop" operation is performed by simply open-
ing circuit breaker K-800. Approximately 2 minutes after the "stop" operation, the
blower B-800 will stop and the standby crystal heater power will be the only power on.
Care must be exercised when working near switch S-808.
In the power amplifier H.Y. supply, an automatic reset overload current relay
K-805 protects this stage from overloading. Relays K-802, and K-803 and K-804 will
function as previously described under normal conditions after relay K-805 has been
opened and automatically closed.
No provision is made to limit the number of recycling periods in the event of
serious overload or short circuit in the high voltage circuit. Therefore if recy-
cling persists, the equipment should be turned off and the source of trouble deter-
mined. The PRIMARY POWER circuit breaker K-800, which is a manual reset overload
breaker protects the entire unit and will open only under much heavier overloads than
the other overload rely K-805. Caution should be taken before closing K-800 after an
overload.
Section IY - 3

B. Bias and Screen Supplies
1. The bias and screen grid power supplies are located on the upper hinged
chassis on the right side of the cabinet; and are shown schematically on
drawing SS-638.
2. Filament voltage is adjusted by the FILAMENT voltage control on the front
panel.
3. Primary voltage to the bias high voltage transformer T-802 is applied be-
tween common lead #10 and control lead #22 which is energized by closing
the "MOD HV" switch. The bias output, after adequate filtering, is con-
nected by lead #48 to the four 250 ohm series connected bleeder resistors
R-805, R-806, R-808 and R-809 whcih are located on the resistor board on
the left side of the equipment. The output of the bias supply is approxi-
mately -200 volts resulting in 50 volt steps across each of the four bleed-
er resistors. Lead #29 connects to this bleeder at the -50 volt point to
provide bias for the 829E tubes in the IPA chassis and lead #30 connects
the -150 volt point to the grid current meter, which in turn connects to the
grid leak resistor R-807.
4. The high voltage winding for the screen power supply is contained in the
main high voltage transformer, the terminals appearing in a row below the
primary terminals. Leads 47 to 49 provide the plate excitation for the
screen rectifier tube V-804, and since the screen high voltage winding is
part of the plate transformer, screen voltage increases with plate voltage.
The DC screen voltage after filtering is connected to both the 50,000 ohm
bleeder resistor P-804 and the series screen resistors R-818 and R-819 by
lead #15. From this point it is connected via the screen current meter and
switch to the screen grids of the power tubes.
C. High Voltage Supply
1. The high voltage anode supply for the power amplifier is obtained from the
high voltage transformer T-803 and the four type 872A rectifier tubes
which are mounted on the phenolic shelf in the base of the cabinet. Plate
voltage is controlled by the PLATE VOLTAGE switch S-816 which is located
on the right control panel.
2. Filament voltage for the high voltage rectifier tubes is adjusted by the
variable transformer YR-800. Indication is provided by the filament volt
meter M-800 which is mounted on the meter panel and should be adjusted to
read 5.0 volts..
3. The rectifier circuit is a conventional single phase full wave bridge. Fil-
tering is accomplished by the use of a double section filter consisting of
L-800, L-801, C-800, and C-801. In addition an auxiliary filter consisting
of C-821 and R-811 and R-812 is connected in series between the high voltage
bus and the negative return of the power supply to damp out any parasitic
oscillations which might be generated by the input choke.
4. The high voltage lead is connected to both the main bleeder resistor R-800
and the high voltage meter multiplier resistor R-801 and the plate circuit
of the power amplifier. The low voltage end of the multiplier resistor is
grounded through a parallel circuit consisting of the 10,000 ohm safety re-
sistor R-802 and the high voltage meter M-803. The function of R-802 is to
Section IV - 4

provide an auxiliary oath to ground for the multiplier current in the event
that the high volta,7e meter movement or any of its associated wiring should
become open circuited, the resistance being high enough not to impair the
meter accuracy, but still low enough to handle bleeder currents.
5. The negative return lead of the power supply is connected to one side of the
filter capacitors C -800 and C-801, the low voltage end of the auxiliary fil-
ter, the safety resistor 8-803 and by lead #46 to the coil of the plate over-
load relay K-805 and then by lead #13 through the plate current meter M-802
to ground. The function of the 500 ohm safety resistor 8-803 is to maintain
a secure ground on the return of the power supply in the event that any of
the inter-connecting wires. - components in the normal return circuit might
become open circuited.
D. Modulator
1. The modulator is diagramed in block fashion by figure #1, and schematically
by drawing SS-638. It consists of the following equipment
CAT.
a. Modulator tower supply 592A
b. Balanced Modulator 587A
c. Audio Panel 586A
d. Multiplier and Single Ended Converter 589
e. Multiplier and Bvlanced Converter 588
f. Semi Final Multiplier 590
g. Intermediate Power Multiplier 590
2. T`.e modulator power supply furnishes filament and plate voltages for the mod,
ulator chassis. On the modulator power supply terminal board; terminal #3
supplies the crystal heater with 6.0 volts AC during standby, and 6.6 volts
DC while operating #4 is the DC filaments for the modulator, #8 is the fila-
ment supply, #9 the regulated 250 volt :)late supply, and #11 the unregulated
450 volt plate supply.
3. The Balanced Modulator Cat. #587A contains a source of low radio frequency
energy Y-200 and V-200, which is differentially phase modulated by V-202
and V-203 ofter amplification by the buffer amplifier V-201. V-204 and
V-205 are tripiers which drive the Multiplier and Single Ended Converter,
Cat. #589, and the Multiplier and Balanced Converter, Cat. #588. The latter
two panels are parallel frequency multiplying channels with a total multi-
plication of 81 times with their frequency deviations separated by 180° and
terminated in a converter stage. If as an example a 200 KC crystal is used
in the balanced modulator panel the input voltages to the two converters from
the channels will be 16,200 KC.
4. The audio panel contains in addition to the audio stages, the control fre-
quency oscillator, the frequency of which is 148 that of the transmitter
output frequency. To continue the example of paragraph 3, assume a control
crystal frequency of 2,000 KC. This voltage is introduced into the balanc-
ed converter and heterodyned with the multiplied input from the first cry-
stal at 16,200 KC. The plate circuit of the balanced converter is tuned to
Section IV - 5

the difference frequency or 14,200 RC. This voltage is combined in the sin-
gle ended converter with the 16,200 KC from the second channel and again the
difference frequency, 2,000 KC, ap-oears in the plate circuit. This voltage
is used to drive the semi-final multiplier panel and has an operating fre-
quency of plus /minus 1,560 cycles.
5. The purpose of this dual conversion is multi-fold;
a. A large amount of multiplication is provided so that the initial Phase
shift in the modulator tubes may be kept as low as possible while at the
same time maintaining a low multiplication of the control frequency os-
cillator thereby producing a stable center frequency. Multiplication
ratios are 7776 over all but only b8 times from the control frequency
crystal.
b. By the use of the dual conversion dual channel system the output fre-
quency of the transmitter becomes independent of the low frequency os-
cillator, its stability being dependent only upon the stability of the
control frequency oscillator.
c. Noise products which are generated in the low frequency oscillator and
buffer amplifier stages are cancelled out in the conversion process
thereby producing noise levels of minus 70 db. below 100% modulation.
d. Since the modulation is applied differentially to each channel the con-
version process results in an additional double in the deviation fre-
quency without the use of an additional multiplier.
6. The Semi -final multiplying panel provides a multiplication of 8 times in two
amplifier and three doubler stages. Its output, and again using the example
above, is 16 megacycles. The final multiplier panel provides a multiplica,
tion of 6 times in a doubler stage, a tripler stage, and an amplifier stage.
The output from this panel for the conditions of the example will be 96 meg-
ac;rcles, which is coupled by a balanced transmission line consisting of RG-.8U
cable to the grids of the power amplifier.
E. Power Amplifier
The power amplifier stage of the model 518 transmitter utilizes 2 Eimac type
4-400A internal anode tetrodes in conjunction with linear circuit elements compris-
ed of short sections of 2 wire transmission lines.
The balanced coaxial coupling line from the final multiplier panel is termina-
ted in a hairpin which in turn is coupled to the grid circuit.
Neutralization is accomplished by resonating the screen grid lead of each tube
to ground with a variable capacitor. Screen voltage is applied to each tube through
a 500 ohm wire wound resistor which acts as a heavily damped choke. Individual screen
currents and total screen current are metered by means of the SCREEN CURRENT meter and
selector switch which are located at the top of the right control panel.
Output coupling from the anode circuit is accomplished by means of a hairpin
mounted on the rear war of the power amplifier compartment. The position of this
hairpin with respect to the plate lines is variable from the right hand control panel
for coupling control. Two air dielectric series capacitors are provided just behind
the hairpin for tuning purposes.
Section IP - 6

Connection of the single 7/8" output transmission line is accomplished just
inside the top of the transmitter proper.
F. Power Output Indicator
The power output indicator is a voltage operated device which provides a rela-
tive indication of transmission line voltage at the point of insertion into the trans-
mission line. The pickup unit is brazed to the short section of transmission line
inside the power amplifier cabinet. It consists of a small adjustable probe, a cry-
stal detector, and RF filters. The indicator is a 1 milliampere meter mounted on the
meter panel, accessible behind the upper right panel of the power amplifier cabinet
for setting a convenient mid-scale meter reading for full power output.
Section IV - 7

BLOCK DIAGRAM OF THE DUAL CHANNEL MODULATOR
TO POWER AMP
GRID CIRCUIT.
I-
aHm
Du,og
U
o
88- 08 MCS.
30 WATTS
A
829B
T^
8298
D
A D
7C7
D D A
MIX T
-I 7C7
-0
T A T
BALANCED
CONVERTER T T A T
Owif".)
záU
CONT. XTAL OSC.
INPUT
TRANS.
PROGRAM LINE INPUT
r- -1 VAR. FREQ. TEMP CONT.
1 TO ADJUST
I
i FIINQCENTER POWER
L__.833-2250 KCS. AMP
PHASE INVERTER
CHOKE AUDIO
CORRECTOR
BUFFER
AMP.
FIRST
TRIPLER
DUAL
CHAN.
INPUT
TRANS
O
O
CHAN. I
CHAN2
XTAL OSC
192-205 KCS. FIRST
TRIPLER
A- AMPLIFIER
D DOUBLER
T- TRIPLER
MIX - MIXER
TRANS.D.0
FIL.SUPPLY FILTER
TRAN. H.V.
PLATE a
FIL. SUPPLY FILTER
FILAMENT AND
PLATE SUPPLY TO ALL
UNITS EXCEPT'bUTPUT"
UNIT.
FILAMENT AND
PLATE SUPPLY
TO OUTPUT UNIT.
FIG. i tFction IV .. F.

SECTION VI
MODULATOR AND POWER AMPLIFIER ADJUSTMENT PROCEDURE
A. MODULATOR LINE UP PROCEDURE
The tuning of the modulator is extremely simple, and ordinarily should require
only a few minutes. In each of the panels the signal direction is from right to
left, and one must proceed this way in alignment. Assuming that complete align-
ment is needed, the following procedure should be followed:
1. Place the voltmeter probe in J-204 and adjust the trimmer on Z-200 until
a voltage is obtained. This serves to indicate that the low frequency
crystal oscillator is operative.
2. With the probe in J-303 go through the Balanced Modulator Chassis, Cat.
#587A from right to left adjusting Z-201, Z-203 and Z- 204'for maximum
drive as read at J-303. Z-202 is not adjusted at this time. See para-
graph 26 for detailed procedure. Then, when Z-300 is peaked the drive at
J-303 should be 20 to 30 volts.
3. With the probe in J-402, Z-205 and Z-400 are peaked for meximum drive.
the voltage at J-402 should be 20 to 30 volts.
4. Return the probe to J-204 and tune the low frequency oscillator tank,
Z-200, until the voltage indicated is zero. It is important that V-201
is not driven into the grid current region, which is indicated by a volt-
age reading at J-204.
5. The multiplier and Balanced Converter, Cat. $588, may now be tuned by ire
serting the probe in J-304 and peaking transformer Z-301 for a 20 to 30
volt indication.
6. Insert the probe in J-305 and peak Z-302 for a 60 to 70 volt indication.
7. With the probe in J-306, peak Z-303 for 35 to 45 volts of drive.
8. Insert the probe in J-307 and peak Z-304 for a reading of 5.0 to 8.0 volts.
9. Insert the probe in J-308 and tune Z-100 in the control crystal oscillator
circuit and Z-305 to maximum. After Z-305 is peaked lower the drive with
Z-100 until 8 to 10 volts at J-308 is obtained.
10. For line up of the Multiplier and Single Ended Converter Cat. +589, insert
the probe in J-403 and peak transformer Z-401 for a 20 to 30 volt indica-
tion.
11. Insert the probe in J-404 and peak Z-402 for a 60 to 70 volt indication.
12. With the probe in J-405, peak Z-403 for 35 to 45 volts of drive.
13. Insert the probe in J-406 and peak Z-404 for a 6 to 10 volt reading.
14. Insert the probe in J-408 and peak Z-306 and Z-406 for a 0.5 to 4 volt indi-
cation.
Section VI - 1

SECTION VI
MODULATOR AND POWER AMPLIFIER ADJUSTMENT PROCEDURE
15. The Semi Final Multiplier, Cat. #590 is now tuned by inserting the probe
in J-501 and peaking Z-405 and Z-500 for 15 to 25 volts of drive.
16. Insert the probe in J-502, and peak Z-501 for 40 to 50 volts.
With the probe in J-503, Z-502 is peaked for 45 to 55 volts. 4 '-
18. z-503 is next peaked for 60 to 70 volts as read at J-504. 2-0
19. Insert the probe in J-505 and peak Z-504 for a 50 to 60 volt indication.
20. The Final Multiplier Cat. 0591A is tuned by inserting the probe in J-601
and peaking Z-505 and Z-600 for 40 to 50 volts. Approximate resonance of
Z-505 may be noted by a slight increase of approximately 1 volt at J-505
as Z-505 becomes resonant.
- 21. With the probe in J-602 the doubler plate and tripler grid are tuned for
120 to 150 volts of drive.
22. Tune the tripler plate for minimum reading on the plate meter, M-600,
(Plate resonance dip.)
23. Insert the probe in J-603 and tune the amplifier grid for maximum drive
repeak both the tripler plate and amplifier grid controls. The amplifier
grid drive should be between 130 and 180 volts, and the tripler plate cur-
rent, as shown on the plate current meter, between 60 to 100 mills.
24. Tune the amplifier plate for minimum reading on the plate meter M-601,
(Plate resonance dip.)
25. Tune Power Amplifier grid circuit and the intermediate Amplifier output
tuning for maximum indication on the Power Amplifier grid meter. Check
Amplifier plate and output tuning and grid tuning for maximum drive. The
grid meter should read 30 to 35 ma. This completes the Modulator tuning
adjustments. A simplified chart of the above adjustments is included on
the next page.
26. Z-202 and Z-407 cannot be adjusted by simply peaking a reading on a volt-
meter. In the absence of proper equipment necessary for their adjustments,
they must be set at the factory marked position, which is not in the least
critical. The equipment required for these adjustments is as follows:
a. Distortionless or very low distortion receiver.
b. Distortion measuring equipment.
c. A means of determining frequency deviation. The REL Cat. #600
Monitor may be used for this or one of the more fundamental
methods may be used.
d. A good, high gain, oscilloscope such as the Dumont 208B.
e. A source of sinusoidal 50 cps.
Section VI - 2

SECTION VI
MODULATOR AND POWER AMPLIFIER ADJUSTMENT PROCEDURE
Z-202 is merely adjusted for minimum distortion, with a modulation fre-
quency of 50 cycles per second and a deviation of plus /minus 75 kc. This
adjustment is very broad and not critical as to distortion.
Z-407 is adjusted by modulating 100% (plus /minus 75 Kc. deviation) at 50
cycles and observing the output of the low distortion receiver on the os-
cilloscope. Make the image very large and observe párticularly the peaks.
Then adjust Z -407 for the purest sine wave peak. If no high frequency hash
is seen on the peaks of the 50 cycles waveform, do not disturb the adjust-
ment of Z-407. Again this adjustment is non-critical making approximately
0.1 db difference in distortion measurements at 50 cycles.
Section VI - 3

SIMPLIFIED CHART OF MODULATOR TUNING
PLACE PROBE
IN
JACK ADJUST APPROXIMATE RANGE
OF CORRECT
INDICATION
ORDER OF
TUNING
OPERATION
J_204 Z -200 (All voltages negative
with respect to ground)
Any voltage
1
J-303 Z-201, Z-203 20 - 30V 2
Z-204, z-300
J_402 Z-205, Z-400 20 - 3ov 3
J-204 Z-200 Muet be zero, 4
J-304 Z-30L 20 - 30v 5
J-305 2-302 6o 7ov 6
J-306 z-303 35 - 45v 7
J-3o7 2-304 5 - 8v 8
J-308 Z-100, Z-305 After tuning Z-305 to
maximum, lower voltage
with Z-100 to 8-10
volts. 9
J_403 2-401 20 - 30V 10
J-404 2..402 60 - 70V 11
J-405 Z-403 35 - 45v 12
J-406 Z-40L 6v - lov 13
J-408 Z-306, z-4o6 0.57 - 4V 14
J_501 2-405, Z-500 15V - 25V 15
J-502 Z-501 407 - 50V 16
J-503 2-502 45 - 55V 17
J_504 2-503 6o - 70v 18
1-505 Z-504 5o - 60V 19
J-6o1 Z-505, z-600 40 - 5ov 20
J-602 Doubler Plate
& Tripler Grid 120 - 150V 21
Section VI - 4

SIMPLIFIED CHART OF MODULATOR TUNING
PLACE PROBE
IN
JACK ADJUST APPROXIMATE RANGE
OF CORRECT
INDICATION
ORDER OF
TUNING
OPERATION
Observe Tripler
Plate Cur. Meter
J-603
Observe Intermediate
Amplifier Plate Cur-
rent meter.
Observe Power Ampli-
fier Grid current
meter.
Tripler Plate
Amp. Grid
Tripler Plate
Intermediate
Amplifier Plate
Intermediate Amp-
lifier Plate, Out-
put tuning, P.A.
Grid tuning.
Tune for dip
66 - 100 Mao
130 180V Drive
Tune for dip
110 - 150 Ma,
30 to 35 Ma Grid
Drive on Power
Amplifier
22
23
24
25
Section VI - 5