Inovonics 630 Manual

OPERATING AND MAINTENANCE
INSTRUCTION MANUAL
MODEL 630
FM RELAY RECEIVER
__________

—–USER’S RECORD —–
Model 630 -Serial No. _______
Date Purchased _____________
Warranty Card Mailed —¨
OPERATING AND MAINTENANCE
INSTRUCTION MANUAL
MODEL 630
FM RELAY RECEIVER
June, 1996
1305 Fair Avenue, Santa Cruz, CA 95060
TEL: [phone] –FAX: [phone]

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TABLE OF CONTENTS
Section I -INTRODUCTION
Model 630 Product Description ........................................................................................... 3
General -Features
Model 630 Technical Specifications..................................................................................... 4
Block Diagram ...................................................................................................................... 5
Section II -Installation and Connection
Unpacking and Inspection ................................................................................................... 6
Mounting ............................................................................................................................... 6
Rack Requirements -Heat Dissipation
AC (Mains) Power ................................................................................................................. 6
As Delivered -Voltage Selector -Power Cord
Radio Frequency Interference (RFI) .................................................................................... 7
Location -Ground Loops
Antenna Considerations ....................................................................................................... 7
The Receiving Antenna -Input Filters
Programming the Receive Frequency ................................................................................. 8
De-Emphasis Selection ........................................................................................................ 9
Audio Loss Delay Jumpering .............................................................................................10
The Composite MPX Output ..............................................................................................10
The Stereo Program Line Output .......................................................................................11
Remote Control Inputs and Alarm Outputs .......................................................................11
Alarm Outputs -Remote Control Inputs -
Analog Metering Outputs
Section III -Panel Controls and Indicators
Panel Controls and Indicators ...........................................................................................13
(All Controls and Indicators Defined According to Function)

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Section IV -Calibration
Calibration ..........................................................................................................................17
Equipment Required -Power Supply Check -Synthesizer
PLL Frequency -Tuner and IF Adjustments -Mute Level Cal -
Composite-Baseband Equalization -Demodulation Separation -
Line Output and Meter Calibration -Multipath Filter Tuning
Section V -Circuit Descriptions
Circuit Descriptions ............................................................................................................22
Component Annotation -RF / IF / Detector Section -
Stereo Decoder -Audio Loss and Multipath Alarms -
Bargraph Meter -Power Supplies
Section VI -Appendix
Frequency Programming Chart -Parts Lists -Schematics -Warranty .....................27

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Section I
INTRODUCTION
MODEL 630 PRODUCT DESCRIPTION
General Inovonics’ Model 630 is a frequency-agile FM “Relay” Receiver
intended for single-channel translator (re-broadcast) service and for
other professional applications requiring high quality off-air program
pickup. The receive frequency is user-programmable over the FM
broadcast band in 100kHz increments.
The 630 has two outputs: a conditioned composite “baseband” output
which may be fed directly to the broadband input of an FM exciter, and
balanced program line outputs which provide demodulated left-and
right-channel stereo audio.
Features Features of the Inovonics 630 include:
•Wide/narrow IF bandwidth which may be locally or
remotely selected.
•A noise-reducing “blend” function for the demodulated
program audio output which may be locally or
remotely enabled.
•Automatic output muting and over-deviation limiting
circuits to protect the re-broadcast signal.
•Alarms with remote outputs for low incoming RF and
for loss of program audio.
•Local and remote measurements of incoming signal
level and multipath distortion for accurate antenna
orientation.
•Accurate front-panel metering of relevant signal levels.

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MODEL 630 TECHNICAL SPECIFICATIONS
Receiver Sensitivity:
10µV for 50dB stereo SNR with
WIDE IF.
Receiver Selectivity:
WIDE IF: –6dB at ±150kHz;
NARROW IF: –6dB at ±75kHz.
(See Figure 1, below.)
Stereo Separation:
WIDE IF: >45dB (typically 50dB),
20Hz–15kHz;
NARROW IF: Typically 20dB,
20Hz–15kHz.
Distortion (in baseband signal or
demodulated audio):
WIDE IF: <0.3% THD;
NARROW IF: <3% THD.
Composite Baseband Output:
Adjustable between 2V p-p and 5V
p-p; 75-ohm source impedance,
unbalanced.
Program Line Outputs:
Left and right channel active-
balanced outputs deliver 0dBm
into 600 ohms at ±75kHz
deviation.
Frequency Response (of de-
modulated program audio):
±0.5dB, 20Hz–15kHz
Noise (in demodulated stereo
program audio):
Better than 60dB below ±75kHz
deviation with 250µV or greater
RF input.
Remote Control Logic:
Individual contact closures to
ground initiate forced-mono
reception, select narrow IF
bandwidth, defeat output muting
and defeat the “blend” feature.
Remote Alarm Provision:
Open-collector NPN transistors
saturate to ground for loss of
carrier and for loss of program
audio.
Power Requirements:
105–130VAC or 210–255VAC,
50/60Hz; 15 watts.
Size and Weight:
1¾”H x 19”W x 7”D (1U);
7 lbs (shipping).
Figure 1 -Receiver RF/IF Bandwidth, WIDE and NARROW Modes.

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BLOCK DIAGRAM
A simplified Block Diagram of the Model 630 is shown below. Receiver
circuitry is explained in detail in the Circuit Descriptions starting on
Page 22, which reference Schematic Diagrams found in the Appendix.

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Section II
INSTALLATION AND CONNECTION
UNPACKING AND INSPECTION
Immediately upon receipt of the equipment, inspect carefully for any
shipping damage. If damage is suspected, notify the carrier at once,
then contact Inovonics.
It is recommended that the original shipping carton and packing
materials be saved for future reshipment. In the event of return for
Warranty repair, shipping damage sustained as a result of improper
packing for return may invalidate the Warranty!
IT IS VERY IMPORTANT that the Warranty Registration
Card found at the front of this Manual be completed and
returned. Not only does this assure coverage of the equip-
ment under terms of the Warranty, and provide some means
of trace in the case of lost or stolen gear, but the user will
automatically receive specific SERVICE OR MODIFICA-
TION INSTRUCTIONS should they be issued by Inovonics.
MOUNTING
Rack
Requirement Inovonics’ Model 630 is packaged to mount in a standard 19-inch equipment rack and requires only 1¾ inches (1U) of vertical rack
space. The use of plastic “finishing” washers is recommended to help
protect the painted finish around the mounting holes.
Heat Dissipation Consuming far less power than an electric coffee grinder, heat
generated by the 630 is insignificant. The unit is specified for
operation within an ambient temperature range extending from
freezing to 120°F/50°C. Because adjacent, less efficient equipment may
radiate substantial heat, be sure that the equipment rack has sufficient
ventilation to keep the temperature below the stated maximum.
AC (MAINS) POWER
As Delivered Unless specifically ordered for export shipment, the Model 630 is set at
the factory for operation from 115V, 50/60Hz AC mains. The rear-
panel designation next to the fuseholder will confirm both the mains
voltage selected and the value of the fuse supplied.
Voltage Selector
A mains voltage selector switch is located beneath the top cover of the
unit and adjacent to the AC mains connector on the circuit board.
With primary AC power disconnected, you may slide the red actuator

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With primary AC power disconnected, you may slide the red actuator
with a small screwdriver so that the proper mains voltage (115 or 230)
is visible. You must always install an appropriate fuse, and check that
the rear-panel voltage/fuse designation is properly marked. It is
factory practice to cross-out the inappropriate designation with an
indelible black marking pen. You can remove this strikethrough with
solvent to redesignate.
BE SURE that the mains voltage selector setting and pri-
mary fuse value are appropriate for the mains supply before
plugging the 630 into the wall outlet.
Power Cord The detachable IEC-type power cord supplied with the 630 is fitted
with a North-American-standard male plug. The individual cord
conductors are supposed to be color-coded in accordance with CEE
standards; that is:
BROWN = AC “HOT” BLUE = AC NEUTRAL GRN/YEL = GROUND
If this turns out not to be the case, we offer our apologies (cord vendors
vary) and advise that U.S. color coding applies:
BLACK = AC “HOT” WHITE = AC NEUTRAL GREEN = GROUND
RADIO FREQUENCY INTERFERENCE ( R F I )
Location Although we anticipate installation of the 630 in the immediate
proximity of broadcast transmitters, you should practice care in
locating the unit away from abnormally high RF fields. This includes
the exercise of common sense when locating the receive antenna as
well. (See additional installation comments in the following Antenna
Considerations subsection.)
Ground Loops With some installations a mains frequency or RF ground loop may be
formed between the antenna or output cable shield grounds and the AC
power cord ground. Use of a “ground-lifting” AC adapter may remedy
the situation, though the chassis ultimately must be returned to earth
ground for safety. Generally, being screwed-down in the equipment
rack will satisfy the safety requirement.
ANTENNA CONSIDERATIONS
The 630 has a rear-panel “F” connector for the receiving antenna. This
is a 75-ohm unbalanced input which should be fed with 75-ohm foil-
shielded coax cable. Appropriate cable and the “F” connector are
standard items with consumer cable-TV equipment in the U.S. and
should be readily available. If the “F” connector is foreign to your area,
feel at liberty to replace it with a more common type.

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The Receiving
Antenna Almost by definition, FM relay (translator) installations are in the fringe of the primary broadcast reception area. This means that a
high-gain, directional receiving antenna must be used if the re-
transmitted signal is to maintain full broadcast quality. This is
particularly important when composite-baseband is re-broadcast
directly. SCA and RDS subcarriers can be degraded, even when the
stereo program sounds fine.
A number of professional FM receiving antennas are available to
broadcasters, and no doubt your preferred equipment distributor can
be coerced into making a recommendation. Be sure to check antenna
impedance, however. A 50-ohm antenna will require a “balun”
matching transformer to properly match a 75-ohm feedline and the
antenna input of the Model 630.
Residential FM antennas should not be ignored for translator
receivers. Something equivalent to the Radio Shack®(Tandy) 15-2163
is a quite acceptable “low-end” choice, and some of the so-called “deep
fringe” consumer FM antennas are really quite good. Many in this
category will exhibit a 300-ohm impedance and will require an
appropriate balun, such as the popular 300/75 matching balun used for
cable connections to older TV sets.
Input Filters Installations which co-locate the re-broadcast receiving and
transmitting antennas may require installation of a notch filter “trap”
in the Model 630 antenna feed. This keeps the transmitter from
desensitizing (or completely “blocking”!) the receiver. The closer the
receive and transmit frequencies, the more likely this is to be a
problem. The “tuned-cavity” trap will probably prove best for this job.
PROGRAMMING THE RECEIVE FREQUENCY
The 630 is tuned by programming the SET FREQ. “DIP” switch beneath
the top cover. This is located on the circuit board directly behind the
front-panel headphone jack. A programming chart is affixed to the
inside of the top cover and shows the DIP-switch settings for each
100kHz frequency increment between 87.9Mhz and 108.1MHz. A copy
of this chart also appears in the Appendix of this Manual on Pages 28
and 29.
The chart has eleven columns of switch settings. These are labeled A
through K and correspond to the first eleven DIP-switch positions which
are similarly labeled in the circuit board legend to the right of the
switch. Each column of the chart contains a 0 or a 1, signifying OFF or
ON, also labeled on the circuit board.
Use a ballpoint pen or small screwdriver to set the switches. To
program a 0, push the switch actuator down-to-the-left, or away from
the large synthesizer chip, IC39. To program a 1, push the switch

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actuator down-to-the-right, or toward IC39. Figure 2, below, illustrates
Model 630 programming for a receive frequency of 103.1MHz.
Figure 2 -DIP-Switch
Programming for 103.1MHz
Station Reception
DE-EMPHASIS SELECTION
The rear-panel left-and right-channel PROGRAM LINE OUTPUT follows
the transmission de-emphasis characteristic. Either the 50-or the 75-
microsecond curve may be selected. The factory setting is proper for the
shipment destination, if this destination is known at the time of
shipping.
De-emphasis selection is made with jumper programming beneath the
top cover. Two jumper strips, labeled JMP2 and JMP3 in the circuit-
board legend, are located about three inches behind the front-panel
MUTE switch. Legend markings designate the proper jumper position
for either 75 or 50 (microsecond) operation. Figure 3, below, illustrates
the two jumpering options.
75µs DE-EMPHASIS 50µs DE-EMPHASIS
Figure 3 -Program De-emphasis Jumpering

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AUDIO LOSS DELAY JUMPERING
The 630 signals a remote alarm for loss of program audio. The delay
between the loss of audio and the alarm output may be set for one, two
or four minutes of “dead air.” This selection is made with a jumper
selection beneath the top cover. The factory setting is for a 1-minute
delay.
The jumper strip, labeled JMP1, is located about an inch behind, and
midway between, the FAULT indicators and the STEREO switch. The
circuit board legend shows the jumper positions for the three timing
delays. Figure 4, below, illustrates the three jumpering options.
1-MINUTE DELAY 2-MINUTE DELAY 4-MINUTE DELAY
Figure 4 -Program Audio Loss Alarm Delay Jumpering
THE COMPOSITE MPX OUTPUT
The composite or “baseband” output is a conditioned, amplified,
wideband output taken directly from the FM detector. It contains the
multiplex stereo program signal along with any SCA, RDS, and/or high-
speed data subcarriers. The rear-panel “BNC” connector labeled
COMPOSITE MPX OUTPUT is an unbalanced output with a source
impedance of 75 ohms. Cable runs from this output should be kept as
short as possible, consistent with providing isolation between the Model
630 receiver and the re-broadcast transmitter. The 630 is capable of
driving 75-ohm cables up to about 100 feet in length. Excessive cable
length can degrade performance, not the worst of which is a loss in
stereo separation.
The COMPOSITE MPX OUTPUT is variable between 2 volts p-p and 5
volts p-p, and is adjusted by the front-panel MPX OUTPUT LEVEL
control. The instantaneous peak value of the received signal at the rear-
panel connector may be observed by setting the front-panel multimeter
to MPX / OUTPUT VOLTS P-P and referencing the lower (volts) scale.
“Conditioning” of the COMPOSITE MPX OUTPUT signal consists of low-
pass filtering and peak-excursion limiting. The low-pass filter is

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amplitude-and phase-flat to 100kHz, serving mainly to eliminate noise
components outside the baseband spectrum. A peak clipping circuit in
the output signal path is factory-set to restrict program peaks in excess
of 130% modulation (±100kHz deviation). This restricts deviation of
the re-broadcast transmission in the event of gross overdeviation or
other problems with the off-air feed.
THE STEREO PROGRAM LINE OUTPUT
The demodulated left-and right-channel stereo line outputs appear at a
6-position terminal block on the rear panel. This connector is labeled
PROGRAM LINE OUTPUT with the LEFT and RIGHT channels identified,
as well as the +and –signal terminals and a G(ground) terminal for
each of the stereo channels. The screw-terminal part of the block may
be unplugged from the chassis; simply grab the portion which protrudes
and pull it straight out. Having a removable terminal block makes
connecting easier and affords a quick disconnect for servicing.
The PROGRAM LINE OUTPUT is active-balanced with a resistive source
impedance of 200 ohms. At 100% modulation (±75kHz deviation) this
output will drive a 600-ohm load to approximately 0dBm. This is a fixed
level and is not affected by the front-panel MPX OUTPUT LEVEL control.
The PROGRAM LINE OUTPUT may be connected to transformer-
balanced or active-balanced inputs. Should you require an unbalanced
output from the 630, use only the +and G terminals from each channel,
do not ground the unused –terminal.
REMOTE CONTROL INPUTS AND ALARM OUTPUTS
A 16-position terminal block affords access to the various logic inputs
and outputs of the 630 Receiver. Like the PROGRAM LINE OUTPUT
connector, this terminal block unplugs from the chassis.
Alarm Outputs
The 630 has alarm output “tallies” for two major fault conditions: loss
of program audio (AUDIO LOSS) and loss of carrier (LOW SIG). The
alarm outputs are redundant to the similarly-designated front-panel
LED indicators. The fault conditions are detailed in Section III under
Panel Controls and Indicators, starting on Page 13.
Each alarm output is an open-collector NPN transistor which saturates
to ground when an alarm condition occurs. The transistor has a
breakdown of at least 40 volts and can sink up to 100 milliamps.
Whatever is connected to the alarm output must supply its own voltage
and “seek” chassis ground from the 630. Adjacent GND (ground)
terminals establish the ground reference. If the output represents
more than a 100-milliamp load, the use of an intermediate relay is
recommended. Any inductive load (such as a relay coil) should include
its own protection against induced back-EMF. This usually takes the

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its own protection against induced back-EMF. This usually takes the
form of a parallel diode properly connected with regard to polarity.
Remote Control
Inputs Four of the operating options may be remotely selected. These are: the narrow IF bandwidth (IF NAR), defeat of the “mute” function (MUTE
DEF), defeat of the “blend” function (BLEND DEF), and “forced
monaural” operation (STER DEF). These options are discussed in
Section III: Panel Controls and Indicators.
Each of the remote control inputs has a 10K-ohm “pullup” resistor to
an internal +9-volt supply rail. A contact closure (or NPN transistor
saturation) to ground will initiate the command. Adjacent GND
terminals furnish a ground reference.
Analog Metering
Outputs To help locate and align the receive antenna, two analog DC voltages have been brought to the rear panel. These are labeled SIG LVL and
MPTH LVL and are proportional to the front-panel multimeter
measurements of signal strength and multipath distortion,
respectively. The DC levels at these outputs are in the 1-volt range.
Like the front-panel meter indications, the DC levels at these terminals
reflect relative measurements of the signal and multipath values. The
idea is to temporarily run these lines to the antenna site where they
can be monitored with a hand-held multimeter. As the antenna is
aimed (rotated and angled up and down) the direct effect on signal
strength and multipath distortion can be conveniently factored into the
alignment procedure.

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Section III
PANEL CONTROLS AND INDICATORS
This section describes the function and operation of all front-panel
controls as they appear, left-to-right, on the front of the 630.
Discussions in this section also explain how and when certain functions
are used, plus other factors which apply to everyday operation. Please,
at least skim this section to verify that our terminology agrees with your
understanding, and to see what we had in mind when certain functions
were incorporated into the 630 design.
POWER Rather than risk insulting our esteemed, technically-
adept users, we have chosen to omit an explanation of
this switch function.
“MULTIMETER” A 27-segment bargraph display monitors several
parameters of the incoming signal. Metering exhibits
peak response to signal waveforms for all
measurements.
The up/down switch to the right of the display cycles
the metering circuit among the measurement
selections. A row of LEDs below the bargraph
indicates the function being measured. These are:
LLeft program channel audio*.
RRight program channel audio.*
L+R Left-plus-right (stereo sum) program
audio.*
* PLEASE NOTE that L, R and L+R
program audio measurements will have
a 100%-modulation, 0dB reference only
when the incoming carrier is deviated
to ±75kHz by a monaural test signal
with a frequency below the influence of
transmission de-emphasis. Stereo
transmissions will have a –1dB
reference, assuming 10% modulation of
the carrier by the 19kHz stereo pilot.
L–RLeft-minus-right (stereo difference)
program audio. This measurement will
generally remain below –10dB with typical
stereo programming.

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MPX
TOTAL
MOD %
This is a fixed measurement of carrier
modulation and references the upper
(percentage modulation) scale. While the
630 lacks the accuracy, resolution and
proper ballistics of a true FM “Mod-
Monitor,” this reading will give a quite
accurate indication of incoming carrier
deviation to the nearest 5%.
MPX
OUTPUT
VOLTS P-P
This measurement shows the loaded peak-
to-peak voltage at the rear-panel
COMPOSITE MULTIPLEX OUTPUT
connector. This voltage level is read on
the lower (volts) meter scale and reflects
the setting of the front-panel MPX OUTPUT
LEVEL control. Though this reading will
follow program modulation, the peak value
shown will be useful in setting the MPX
OUTPUT LEVEL to an approximate figure
required by the re-broadcast exciter input.
SIGNAL Signal strength of the incoming carrier is
shown with this metering selection. This
is a relative measurement only and none of
the meter scales applies. Use this
measurement to align the receive antenna
for maximum signal and to monitor signal
variations due to weather, other
miscellaneous acts of God, and totally
inexplicable phenomena.
MULTI-
PATH This selection gives a quantitative readout
of multipath distortion in the received
signal. Like, the SIGNAL measurement,
MULTIPATH is a relative reading. This
measurement is useful in orienting the
antenna to minimize multipath effects.
FAULT LOW
SIGNAL Whenever the received signal falls to a
level of approximately 10µV, a LOW
SIGNAL alarm is registered. This lights
the LOW SIGNAL front-panel FAULT
indicator and provides a remote-alarm
ground at the rear-panel LOW SIG
terminal. Alarm logic also operates the
optional MUTE function.
This circuit has a certain amount of built-
in hysteresis. Once a low-signal condition
is sensed, the incoming carrier must
return to approximately 20µV to reset the
alarm and un-mute the outputs.

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AUDIO
LOSS An extended loss of program audio will
light the AUDIO LOSS indicator. L+R
(stereo sum) program audio must remain
below –20dB (10% modulation) for the 1, 2
or 4 minute pre-programmed delay. (See
Audio Loss Delay Jumpering on Page 10.)
Loss of audio also applies ground to the
rear-panel AUDIO LOSS terminal for a
remote alarm.
MULTI-
PATH This indicator is associated with multipath
distortion measurement circuitry. It is
calibrated to light whenever the level of
multipath distortion exceeds a value which
has been shown to compromise acceptable
stereo (and subcarrier) performance.
STEREO The STEREO switch simply defeats the stereo decoder
circuitry for the left-and right-channel program line
outputs only. It has no effect on the composite-
multiplex output signal. A ground applied to the rear-
panel STER DEF terminal will also place the 630 in a
forced-mono reception mode. The front-panel DEFEAT
and ENABLE LEDs will always indicate the actual
reception mode, whether selected by the front-panel
switch or by the rear-panel terminal.
In normal STEREO / ENABLE operation, the yellow
LED at the far-right of the STEREO switch lights when
a stereo broadcast is received.
BLEND This feature is part of the stereo decoder circuitry. It
has no effect on the composite-multiplex output, only
on the demodulated left and right program audio
outputs.
This “blend” function is a bit more sophisticated than
the similar feature incorporated into consumer
automobile FM receivers. Most simple circuits merely
blend stereo programming to monaural as the carrier
level drops. The 630 decoder instead samples noise in
the 53kHz to 100kHz composite spectrum to
determine how much of the stereo program should be
blended to mono to lessen the audible noise in the
demodulated output. This feature can help maintain
audio quality when conditions deteriorate due to
weather, etc. It can be locally defeated by the BLEND
switch, or remotely by grounding the rear-panel BLND
DEF terminal. In either case, the ENABLE and
DEFEAT indicators will show the function status.

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MUTE With the MUTE switch set to ENABLE, both the
composite-multiplex output and the left-and right-
channel program line outputs are muted when a fading
carrier triggers a LOW SIGNAL alarm. (See discussion
under FAULT indicators.)
This MUTE function may be locally disabled by setting
the front-panel switch to DEFEAT, or remotely by
grounding the rear-panel MUTE DEF terminal. The
ENABLE and DEFEAT indicators confirm circuit status.
The yellow LED to the far-right of the switch signals a
“muted” condition.
IF BANDWIDTH IF bandwidth, nominally WIDE or NARROW,
determines receiver selectivity. WIDE is the normal
operating mode with best distortion and stereo
separation specifications. (See Specifications, Page 4.)
NARROW bandwidth should be used only when strong
adjacent-channel interference is encountered. The
NARROW mode degrades stereo separation to about
20dB! Also, harmonic distortion in NARROW can
reach 2% or more, and intermodulation between
program audio and any subcarriers may render the
subcarrier service unusable.
The front-panel IF BANDWIDTH switch sets the
selectivity characteristics with LED verification of
selection. When the switch is left in the WIDE position,
a ground applied to the rear-panel IF NAR terminal will
change the selectivity to NARROW and light the
appropriate LED.
MPX OUTPUT LEVEL This multi-turn control sets the level of the composite-
multiplex output signal at the rear-panel COMPOSITE
MPX OUTPUT connector. The peak-to-peak output
level may be observed with the bargraph multimeter
(as it is being adjusted) by selecting MPX / OUTPUT
VOLTS P-Pmetering.
PHONES Buffered left-and right-channel program audio is fed
to the front-panel PHONES jack. This level is preset
for a headphone volume which should be adequate for
identifying and qualifying the received program signal.
Either 8-ohm or medium-impedance “professional”
headphones may be plugged into this jack.

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17
Section IV
CALIBRATION
The Model 630 Relay Receiver does not require routine calibration. In
normal operation the 630 can be expected to maintain its specification
over an indefinite period.
Should a catastrophic failure occur, necessitating replacement of
component parts in critical circuits, return to proper operation may be
confirmed by following the adjustment procedure given below.
Equipment
Required •Dual-Trace Oscilloscope —5mV sensitivity, 20Mhz bandwidth, 10:1 probe.
•RF Generator —FM-stereo test signal source with internal audio
modulation, accurate deviation readout, and a variable, calibrated
RF output. This should be a “laboratory-grade” instrument, not
some dusty old derelict from a TV repair shop.
•Digital Multimeter
•AC Voltmeter —with dB scaling.
•Audio Distortion (THD) Analyzer
•Audio Generator —20Hz–20kHz range; variable output.
•Frequency Counter —capable of exact frequency measurement
to 5Mhz.
•“Precision” FM-Stereo Demodulator —station Mod-Monitor
with input for composite-baseband signal. (Must be able to resolve
separation to at least 50dB.)
Power Supply
Check 1. Apply power to the 630.
2. Check that the positive and negative 9-volt regulated supplies are
between 8.5V and 9.0V. You can check these on pin 8 (positive) and
pin 4 (negative) of any 8-pin IC, except IC38.
3. Check the +5-volt supply on pin 1 of the synthesizer prescaler,
IC38. This should measure between 4.5V and 5.0V.
4. Check the LED supply. Measure between pin 3 (+) and pin 2 (–) of
IC2. The voltage should read between 20V and 24V.
Synthesizer PLL
Frequency Using a low-capacitance ‘scope probe, monitor pin 26 of IC39 with the frequency counter. Adjust C94 for exactly 3.2000MHz.
Tuner and IF
Adjustments
1. Turn the front-panel MUTE and BLEND switches to DEFEAT and the
IF BANDWIDTH to WIDE.
2. Set the receive frequency to mid-band: 98.1MHz. From top-to-
bottom (A through K) of programming DIP switch S7, this
is: 11111101110. (“1” is ON, or down-to-the-right; “0” is OFF, or

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is: 11111101110. (“1” is ON, or down-to-the-right; “0” is OFF, or
down-to-the-left)
3. Set the RF Generator to this same frequency and feed it to the
antenna input of the Model 630.
4. Set the bargraph metering to read SIGNAL (RF signal strength) and
apply full output from the RF Generator. This should drive the
bargraph display to the 0dB point. Then decrease the output until
the 0dB LED just goes out.
5. Modulate the RF Generator with a 400Hz monaural test signal at
100% modulation (±75kHz deviation). (This must be monaural
modulation without the 19kHz stereo pilot.)
6. Monitor the rear-panel COMPOSITE MPX OUTPUT with the
Oscilloscope and Audio Distortion Analyzer. Set the front-panel
MPX OUTPUT LEVEL control for an output of 4 volts p-p.
7. Adjust quadrature coil L3 for a peak in the waveform level and a
null in the indicated THD. Distortion at full modulation should be
under 0.25%.
Mute Level Cal This adjustment procedure directly follows the preceding one.
1. Set the front-panel MUTE switch to ENABLE.
2. Reduce the RF Generator output to exactly 10µV. Make sure that
this is the loaded level which is actually applied to the rear-panel
75-OHM ANTENNA connector.
3. Set trim control R149 at a point where the MUTE and the LOW
SIGNAL indicators just come on. Check circuit hysteresis. As the
RF Generator output level is turned up and down, the indicators
should turn on at 10µV and off at approximately 20µV.
Composite-
Baseband
Equalization
1. Reset the RF Generator to the “nearly full” RF output level (just
under 0dB SIGNAL bargraph indication) and 100% monaural
modulation at 400Hz. Monitor pin 14 of IC29 with the AC
Voltmeter.
2. Adjust R187 for 400mV r.m.s. After this is adjusted disconnect the
ACVM.
3. Connect the rear-panel COMPOSITE MPX OUTPUT of the Model 630
to the composite-baseband input of the Modulation Monitor. Adjust
the MPX OUTPUT LEVEL control of the Model 630, and/or the input
level control of the Mod-Monitor, for a Total (peak) Modulation
indication of 100% (±75kHz deviation).
4. Reset the RF Generator for stereo transmission, audio modulation
frequency to 1.5kHz. The 630 should indicate stereo reception. If
necessary, decrease the audio modulation level of the RF Generator
to maintain 100% total modulation (±75kHz deviation).
5. Set the RF Generator for left-channel-only modulation, and the
Mod-Monitor to show stereo separation.