QEI 675 User manual
www.SteamPoweredRadio.Com
TABLE
OF
CONTENTS
,
SECTION
1
GENERAL
INFORMATION
1-1
.Description
1-2
Electrical
S~ecifications
1-3 Mechanical
Spedfications
1-4 Instrument
[dentification
1-5
Acces
so
•
ri
es
SECTION
2
INSTALLATION
2-1
Initial
Inspection
2-2 Preparation•for
Use
2-3
Repacking
for
Shipment
SECTION
3
OPERATI.ON
3-1
Operator Controls
and
Indicators (Front
Panel}
3-2 Controls
and
Connections (Rear Panel}
3-3
Initial
Operation
3-4
Normal
Operation
-
SECTION
4
THEORY
OF
OPERATION
4-1
General
4-2 Detail
Circuit
Destription
SECTION
5
ALIGNMENT
AND
TROUBLESHOOTING
5-1
Equipment
Required but
Not
Supplied
5-2
FMO
and
Phase
Lock
Assembly
Alignment
5-3
Power
A~plifier
Alignmen~
5-4 Exciter-Transmitter.Interface
5-5 Troubleshooting
5-6
Power
Tran~fo~mer
Wiring
SECTION
6
PARTS
LISTS
SECTION
7
SCHEMATICS,
LAYOUTS,
WAVEFORMS
SECTION
8
OPTIONS
www.SteamPoweredRadio.Com
-
-
SECTION
l
-
GENERAL
INFORMATION
1-1
DESCRIPTION
1-2
The
QEI
Type
675
FM
Exciter
is
an
all
solid
state,
on
carrier
direct
FM~
phase locked, frequency synthesized
exciter
designed
to
meet
or
exceed the
FCC
requirements
for
use in the standard
FM
broadcast
band
(88-108
MHz).
The
Exciter
may
be
programmed
to operate
on
any
100
KHz
increment in the
FM
band
using the
same
high
stability
8
MHz
crystal
as .a reference.
The
Exciter
is
manufactured in a standard
3½
11
X
19
11
rack
mount.
All
operator
controls,
adjustments
and
indicators
are
located
on
th~
front
panel. Signal
input
and
output connections,
fuse,
AC
power
and
the
MONO-COMP
switch are
lo-
cated
on
the
rear
panel.
The
Exciter
is
all
solid
state,
employing
silicon
transistors"
diodes
and
in-
tegrated
circuits.
The
Exciter
features
phase locked stabil.,ity
and
on
carrier
direct
FM
for
full
multiplex operat,ion with freedom
from
spurious responses.
The
Power
Amplifier
is
capable
of
withstanding
any
magnitude or·phase
of
VSWR
.
and
the
power
output
is
adjustable
from
less
than 5 to
greater
than
20
watts.
ELECTRICAL
SPECIFICATIONS
Primary
Power
Power
Consumption
Power
Output
Frequency
Range
Type
of
Emission
Modulation Capability
(less
than
1%
THO)
Frequency
Stability
Output
Impedance
VSWR
Protection
Harmonic
and
Spurious
Suppression
l05-125/210-250
Vac
50/60
Hz.
Approximately
50
watts
max.
Adjustable
from
less
than.5
to
greater
t.
han
20
watts.
88
MHz
to
108
MHz
(programmable).
180F3
or
300F9.
150
KHz
peak.
+
500
Hz
(-10°C
to
+55
6C).
50
·
Ohms.
Any
magnitude
or
phase.
Better
than
80dB.
-3-
I
www.SteamPoweredRadio.Com
1-3
Mono
Input
a.
Impedance
b.
Level
c. Pre-emphasis
Stereo Input
a.
Impedance
b.
Level
SCA
Inputs (2)
600
Ohms
(balanced).
+10
dBm
for
75
KHz
dev.
@400
Hz.
75
usec + 1
dB
(50
usec
optional).
lOK.
4V
pp
for
75
KHz
de
viation.
a
a.
Impedance
------
lOK.
b.
Le
vel
""T"
Distortion
FM
Noise
(below
75KHz
dev.
with
75
usec de-emp.)
AM
Noise
Stereo Separation
Crosstalk
(Main
to
SCA)
Crosstalk
(SCA
to
Main)
Environmental
MECHANICAL
SPECIFICATIONS
Dimensions
Mounting
Dimensions
Net
Weight
Shipping
Weight
Maximum
Operating
Temp.
JYp
p
for
10%
inj
ection.
0.35%
max.
THO@
75
KHz
dev.
Better
than
-70dB.
Better
than
-55dB.
Better
than
40dB
from
30Hz
to
15KHz
with
QEI
Model
772
Stereo Generator.
-55dB.
-65dB.
0°C
to
+55°C
operating. (-15°C to
+55°C
with
30
minute
warm
up.)
3½"H
X
19"W
X
14
11
D.
Figure 2-1.
13 pounds
17 pounds
131°F
(55°C)
Ambient.
-4-
www.SteamPoweredRadio.Com
1-4
INSTRUMENT
IDENTIFICATION
This
unit
is
identified
by
a
Model
Number
and
a
six
digit
serial
number
located
on
the
rear
panel.
All
correspondence
to
your
sales
representative
or
the
factory
in regard
to
this
unit
should
reference
the complete
Model
and
Serial
Numbers.
1-5
ACCESSORIES
The
Exciter
may
be
used -as a
10
Watt
Transmitter
with the accessory
Meter
Panel. This Panel contains Final
Amplifier,
and
Incident
and
Reflected
Pow-
er
,Metering, di~ectiorial ~oupler ~nd ~ignal sampler.
-5-
www.SteamPoweredRadio.Com
SECTION
2
INSTALLATION
2-1
INITIAL
INSPECTION
Check
the shipping carton
for
external
damage.
If
the carton
exhibits
evi-
dence
of
abuse in handling
(holes,
broken
corners,
etc.)
ask the
carrier
agent to
be
present
when
the
unit
is
unpacked. Carefully
unpack
the
unit
and
inspect
all
equipment
for
physical
damage.
Immediately
after
unpacking,
any
bent or broken
parts
or
scratches
should
be
noted.
Keep
all
packing
material for proof
of
damage
claim
or
for possible future use.
2-2
PREPARATION
FOR
USE
The
unit
is
designed to
be
mounted
in a standard
19
11
rack. Air space should
be
provided
above
and
below
the
unit
so
that
heat generated
by
the
circuitry
may
be
dissipated.
Additional cooling
may
be
required
if
the
unit
is
placed
above high heat generating equipment in order to
keep
the ambient temperature
below
the
maximum
specified.
Mount
the
unit
to the rack using (4)
#10
countersunk screws
and
finishing
washers.
The
unit
requires a
105-125V
single
phase,
50
oi
60
Hz
power
source
or
a 210-
250V
single
phase,
50
or
60
Hz
power
source.
The
identification
place
on
the
back
panel
shows
for
which
power
source the
unit
is
wired.
See
Section 5-5
for
information
on
changing
taps.
Connect a
suitable
50
ohm
RF
load
to
RF
OUT
jack Jl using a type N connector
and
RG-8/U
or equivalent cable.
tonnect
Mono
audio.
line
to
TBJ
and/or Stereo
Generator ·:to
COMP
jack J2. Connect
SCA
Generator
to
either
SCA
jack J3
or
J4.
Connect
AC
power
plug
to
·approp~iate
power
source.
C A UT I O N
When
connecting the Exciter to the Transmitter, tuning
of
the
transmitter
input
circuitry
will
be
facilitated
by
the use
of
a
3dB
30
watt
pad
and
a
thru-line
wattmeter
between
the Exciter
and
-the Transmi~ter.
If
these-devices are not a-
vailable
reduce the output
power
of
the
exciter
and
tune the input
of
the
trans-
mitter
until
a
somewhat
reasonable
match
is
obtained.
If
the
transmitter
is
al-
ready tuned to
exciter
frequency a
11
touch
up
11
adjustment should
b{
all
that
is
necessary.
If
the
IPA
of
the
transmitter
can
be
mistuned to the point
of
os-
cillation
be
sure to use the
3dB
pad.
It
is
possible to drive
large
amounts
of
power
back
into
the Exciter
from
an
oscillating
IPA
thereby destroying the out-
put
transistor.
-6-
www.SteamPoweredRadio.Com
In
some
transmitters
it
is
possible to overdrive the
IPA
of
the
transmitter
causing
it
to
break
up.
Therefore,
you
should
keep
the
PWR
ADJ
control
of
the
exciter
at
minimum,
then slowly increase
it
until
the
IPA
of
the
trans-
mitter
indicates
the
same
amount
of
grid
current
as with your previous ex-
citer.
The
final
stage
of
the
transmitter
can
be
tuned
for
full
output
at
this
time.
2-3
REPACKING
FOR
SHIPMENT
NOTE:
Before returning a
unit
for
repair
or
calibration,
contact
the factory
or your authorized
representative
for a Return Authorization. Attach a tag
showing
owner's
name
and
address. A description of the
service
required should
also
be
included. Unit must
be
shipped prepaid
and
insured
for
full
value.
Use
the
original
shipping carton
and
packing material
for
re-shipment.
If
they
are
not
available,
proceed as follows:
A.
Use
a carton with
minimum
test
strength
of
250
lbs.
B.
Use
heavy
paper
or
sheets
of
cardboard to
protect
all
surfaces.
C.
Use
at
least
four inches
of
tightly
packed shock absorbing material
such as
extra
firm polyurethane
foam
or rubberized
hair.
NEWSPAPER
IS
NOT
SUFFICIENT
CUSHIONING
MATERIAL.
I
D.
Use
heavy reinforced shipping tape to secure the outside
of
the
carton.
E.
Use
large
FRAGILE
labels
on
each
surface.
-7-
www.SteamPoweredRadio.Com
SECTION
3
OPERATION
3-1
OPERATOR
CONTROLS
AND
INDICATORS
(FRONT
PANEL)
l.
POWER
Switch
Sl
and
POWER
Indicator
CR2
This switch controls primary
power
to
the
unit.
The
LED
(CR2)
will
light
indicating
power
on.
If
the
LED
flashes,
it
indicates
a
power
supply overload or
an
extreme
RF
load mismatch.
2.
MULTIMETER
Switch
S2
and
MULTIMETER
Ml.
3.
4.
This switch controls the function monitored
by
the meter. A
list
of
multimeter readings
is
supplied
by
the
factory
with each
unit.
Since
these readings are only a
relative
indication,
it
is
recommended
that
they
be
checked
and
logged
periodically
so
that
any
excessive deviation
from
normal
will
be
recognized.
PWR
ADJ
Control
Rl
This screwdriver adjustment
can
be
used
to
vary the
RF
output
from
less
than 5 watts to over
20
watts.
If
the Exciter
is
to
be
used
below
app-
roximately
12
watts output,
it
is
recommended
that
the tap
on
the
power
transformer secondary
be
moved
to the
75%
point. This will
limit
the
maximum
output
power
to
less
than
12
watts but will cut
down
on
the
pri-
mary
power
consumed
and
lower heat
dissipation
within the
unit.
See
Section 5-6.
FREQ
ADJ
Control
R2
This screwdriver adjustment
can
be
used to
fine
tune the Exciter over a
range
of
approximately
2:_
500
Hz.
5.
AFC
LOCKED
Lamp
DSl
and
Socket
XDSl
This
lamp
indicates
when
the
FMO
is
.locked
to
the reference
crystal
·
as"".
cillator.
If
the
FMO
is
not locked
to
the
reference,
sensing
circuitry
will extinguish
lamp
DSl
and
shut
down
the
RF
output
of
the Exciter.
It
is
normal
for
this
lamp
to
light
and
RF
power
to appear within a
few
se-
conds
after
the Exciter
is
energized.
3-2
CONTROLS
AND
CONNECTIONS
(REAR
PANEL)
l.
MONO/COMP
Switch
S3
This .switch
selects
either
the
mono
or
stereo
input
signals.
In
the
mono
position,
the input signal
is
automatically pre-emphasized in accordance
with the
75
usec curve.
-8-
www.SteamPoweredRadio.Com
2.
RF
OUT
Jack
Jl.
3.
COMP
Jack J2.
Approximately
4Vpp
across
lOK
is
required for
75
KHz
deviation.
4.
SCA
Jacks Js
and
J4.
Approximately
lVpp
across
lOK
is
required for 7.5
KHz
deviation.
5.
METER
Jack J5.
This jack provides access
to
the
PA
voltage
and
current
information
re-
quired
by
the optional meter panel. This panel
is
used
when
the Exciter
is
used
as a
low
power
transmitter.
6.
TBl.
7.
This
is
a
600
ohm
balanced audio input.
+10
dBm+
l
dB
is
required
for
75
KHz
deviation
at
400
Hz.
This input
is
always-pre-emphasized.
The
center terminal
of
TBl
is
connected to chassis ground.
FUSE
Fl
and
XFl.
This
is
the primary
power
fuse
for
the
unit.
It
is
the only fuse nec-
essary since
all
power
supplies are
short
circuit
protected.
It
should
be
replaced only with a fuse
of
the
same
type
and
rating
as the
original
(3AG
lA).
3-3
INITIAL
OPERATION
l.
Operate
POWER
switch
and
verify
that
LED
CR2
is
lit.
2.
Verify
that
AFC
LOCKED
lamp
lights
and
RF
output appears within a
few
seconds.
3.
Check
MULTIMETER
readings
against
factory supplied information.
Read-
ings should agree
within.:!:_
10%.
NOTE:
The
RF
reading will vary
somewhat
depending
on
the
RF
load connected to the
Exciter.
3-4
NORMAL
OPERATION
For
normal
operation,
use
PWR
ADJ
Control
Rl
to
set
power
output to level
required.
Check
MULTIMETER
readings
periodically
to
verify
that
no
drastic
changes
have
taken place.
-9-
www.SteamPoweredRadio.Com
Use
FREQ
ADJ
control
R2
to fine tune Exciter
to
exact frequency.
Remember
that
a phase locked Exciter
does
not
exhibit
the
drift
of
a frequency lock-
ed
exciter.
Be
sure
that
any
frequency
error
is
in the Exciter
and
not in
the measuring instrument before
you
attempt
to
tune the
Exciter.
Use
signal
levels
in Section 3-2 to get approximate
100%
levels
and
use
an
FCC
Type
Approved
modulation monitor
QEI
Model
671
(with
Model
771
for
stereo)
or
equivalent
for
exact determination
of
modulation.
-10-
www.SteamPoweredRadio.Com
SECTION
4
THEORY
OF
OPERATION
4-1
GENERAL
Refer to block diagram
of
the
Exciter.
The
Exciter
circuitry
is
on
three
circuit
boards:
A2-FMO
and
Phase
Lock
Assembly;
A3-IPA
and
PA
Assembly;
and
A4-Power
Supply Regulator Assembly.
1.
A2
FMO
and
Phase
Lock
Assembly.
A packaged
on
carrier
direct
FM
oscillator
sub-assembly produces
the basic
signal.
This signal
is
amplified
by
the
FMO
buffer
and
control
amplifier
to a level
of
approximately
100
mw.
A sample
of
this
signal
is
fed to a high speed
divider
which
reduces the
fre-
quency
to
nominally 5
MHz
(fc/20).
This 5
MHz
signal
is
then pro-
cessed
by
the programmable
divider
whose
output
is
5
KHz
regardless
of
the assigned frequency.
The
output
of
an
8
MHz
crystal
controll-
ed
oscillator
is
digitally
divided to 5
KHz.
This signal
is
phase
compared
with the output
of
the
programmable
divider
and
the
re-
sulting
signal
is
filtered
and
used
to
control the
FM
oscillator
sub-assembly. Thus, the
programmable
divider
allows the use
of
the
same
high
stability
8
MHz
reference
crystal
regardless
of
channel
assignment.
It
should
be
noted
that
a phase locked loop required a phase
error
not a
frequency
error
to
generate
its
correction
signal.
Because
of
this-:-t"he
output of a phase locked
exciter
exhibits
long term phase coherence with
the reference
oscillator
without the frequency
drift
associated with
fre-
quency
locked loop
exciters.
·
Circuitry
is
included
that
senses lock
and
provides a signal
that
cuts
off
the control
amplifier
thereby
shutting
off
the
RF
output
until
lock
is
es-
tablished.
2.
A3-IPA
and
PA
Assembly.
This board contains a
two
stage
amplifier
which
raises
the
100
mw
output
of
the
A2
assembly
to
a level
of
20
watts~ -
The
transistors
are
of
the
emitter
ballasted
type
and
this
in conjunction with the
circuit
and
power
supply design allow operation
into
any
magnitude
or phase
of
VSWR
without
damage.
However,
good
operating
practice
dictates
that
this
VSWR
protection
not
be
abused.
Do
not knowingly
operate the Exciter without a proper
RF
load.
-11-
www.SteamPoweredRadio.Com
3.
A4-Power
Supply Regulator
Assembly.
This board contains three
power
supplies.
The
IPA-PA
power
supply
regulator,
the
+l5V
FMO
regulator
and
the
5V
FMO
logic
regulator.
All
of
these supplies are short
circuit
protected.
The
IPA-PA
sup-
ply
can
be
varied
from
approximately
14V
to
24V
using the
PWR
ADJ
control
for
the purpose
of
controlling
the output
power
of
the
Exciter.
4-2
DETAIL
CIRCUIT
DESCRIPTION
l.
A2
FMO
and
Phase
Lock
Assembly.
The
output
of
the
FMO
sub-assembly
is
fed
to
the base
of
Ql, the
FMO
buffer.
This stage drives
Q3,
the control
amplifier
and
Ul,
a high speed
emitter
coupled logic
(ECL)
flip-flop.
Q3
raises
the
power
level
to
approximately
100
mw,
a level
sufficient
to drive
the
IPA.
If
an
unlocked condition
is
sensed, a signal
is
devel-
oped
which
causes
Q2
to conduct thereby shorting the base
of
Q3
to
ground
and
shutting
off
the
RF
output.
Q4
provides level matching
between
the output of
Ul
(fc
7
2)
and
the input
of
U2.
U2
is
a high speed divide
by
10
circuit.
The
output
of
U2
is
therefore
fc7
20.
U3,
U4,
U5
and
U6
make
up
the
prograITJTiable
divider.
By
grounding the appropriate points (as
shown
in Table
5-l
),
this
circuit
can
be
made
to
divide
by
any
whole
number
from
2 to
2000.
For
operation in the
FM
band, the
circuit
is
made
to
divide
by
a
number
between
881
and
1079.
When
this
is
done, the output frequency
of
the prograrrmable
divider
is
5
KHz
when
the
FMO
is
operating
on
the assigned channel.
Q7,
Yl
and
associated
circuitry
form
a
stable
8
MHz
crystal
os-
cillator
which
provides the reference frequency
for
the system.
C27
is
the coarse tune
capacitor
and
QB
(a
transistor
used as a
varicap) provides the voltage
controlled
fine
tuning.
QB
is
con-
trolled
by
the
FREQ
ADJ
pot
on
the
front
panel.
Q9
buffers the
output
of
the reference
oscillator
and
provides level matching to
drive
U7.
U7,
U8
and
U9
are
TTL
integrated
circuits.
The
output
of
U9
is
8
MHz
7
1600
or
5
KHz.
This 5
KHz
square
wave
is
diff-
erentiated
and
applied to
Q7.
When
Q7
conducts,
it
discharges
C21.
C21
is
charged through constant
current
source
Q6,
R46
and
R47.
The
result
of
this
action
is
to convert the 5
KHz
square
wave
to
a
linear
5
KHz
sawtooth.
R47
is
an
amplitude
and
linearity
ad-
justment.
The
5
KHz
output
of
the
programmable
divider
drives pulse amplifier
Q5.
The
output of
Q5
and
the sawtooth converter
are
coupled to
Ul2.
This
IC
and
associated
circuitry
form
a "sample hold" phase
detector.
Ul2
is
a gated Operational Transconductance Amplifier. This device
has
a high
impedance
(constant
current)
output.
R39
and
C20
form
a
-12~
www.SteamPoweredRadio.Com
2.
3.
storage
circuit.
Ul2
charges
this
storage
circuit
to the point
on
the input sawtooth
which
is
coincident with the pulse
from
QS.
There-
fore,
as the phase angle between the reference derived
and
the
FMO
derived S
KHz
signals
changes, the voltage
on
C20
rides
up
or
down.
However,
since the voltage
can
change only
when
the pulse
from
QS
is
present,
the
filter
required to
eliminate
the reference frequency
is
greatly
reduced.
Ull
is
a high input
impedance
voltage follower
which
eliminates
any
loading
of
the storage
circuit.
The
low
imped-
ance output of
Ull
is
filtered
and
applied to the
AFC
control
port
of
the
FMO
sub-assembly thereby closing the control loop.
QlO
buffers the output
of
U9
(reference
S
KHz)
and
drives the
REF
position
on
the
MULTIMETER.
UlO,
Qll
and
Ql2
dorm
the
circuit
that
senses lock. -
AS
KHz
square
wave
from
U9
and
a S
KHz
pulse
from
the
programmable
divider
are
fed
to
UlO.
If
the
two
inputs are not locked, a square
wave
will
appear
at
pin 6
of
UlO.
This signal
is
converted to a
DC
level
by
Qll
and
this
level
is
applied
to
Ql2
which
drives the
other
half
of
UlO.
The
output
of
UlO
is
then fed
to
Q2
where
it
shuts
down
the
RF
output
and
to
Ql3
which
turns
off
the
AFC
LOCKED
lamp.
A3
IPA
and
PA
Assembly
The
output of the
A2
Assembly
(approximately
100
mw)
is
applied to
Tl.
Tl
and
T2
provide impedance matching
to
the base
of
Ql, the
IPA.
C2
stabilizes
the
amplifier
throughout the
power
adjust
range.
C7,
C8
and
L2
provide impedance matching
between
the
collector
of
Ql
and
the base of
Q2,
the
PA.
LS,
Cl4
and
ClS
provide
impedance
match-
ing
between
the
collector
of
Q2
and
the load.
CRl
and
associated
circuitry
drives the
RF
position
on
the
MULTIMETER.
Parallel
bypass
capacitors
are
used
on
both stages
to
insure
that
the
power
supply
is
bypassed for
all
frequencies. This precaution
is
necessary
due
to the extremely high
low
frequency gain
of
RF
power
transistors.
If
adequate bypassing
is
not used,
low
frequency
oscillations
of
a
sufficient
magnitude to destroy the
transistor
can
occur.
Do
not
operate the Exciter with
any
of
these bypass capacitors disconnected.
Although the
PA
can
withstand
VSWR
without
damage,
good
operating
practice
dictates
that
the
Exciter
should not knowingly
be
operated
without a proper load.
A4
Power
Supply Regulator Assembly.
a.
IPA-PA
Regulator
A
12
volt
zener diode,
CR4,
is
the reference for
this
supply.
The
PWR
ADJ
control
Rl
(front
panel
control)
supplies
all
or
part
of
the
12
volts
across
CR4
to
the base
of
Q2.
Q2
and
Q3
form
a
DC
amplifier
with a gain
of
approximately 2. This
raises
the voltage supplied
to
the base
of
pass
transistor
AlQl
(mtd.
on
heat sink
on
rear
of
unit)
to
approximately 24.7
volts
max.
-13-
www.SteamPoweredRadio.Com
b.
c.
The
emitter
of
the pass
transistor
supplies the load through
Rl2.
If
the
current
drawn
through
Rl2
is
excessive,
the
volt-
age drop across
Rl2
will
exceed the forward voltage necessary
to
cause
Q4
to
conduct.
When
Q4
conducts,
it
fires
SCR
CR3
which
shorts
out the reference thereby causing the supply
to
shut
down.
When
this
occurs,
Cl
starts
to
charge through
Rll.
When
the voltage
at
the junction
of
Rll
and
Cl
becomes
more
negative than the gate voltage
of
SCR
CRl,
CRl
fires
discharg-
ing Cl.
The
resulting
pulse causes
Ql
to
momentarily
interrupt
the holding
current
through
CR3
thereby
cutting
off
CR3.
This
action
resets
the supply automatically.
15
Volt Regulator
Zener diode
CR6
is
the reference for
this
regulator.
Q5
and
Q7
amplify the voltage across
this
diode
to
approximately
15
volts.
Q6
acts
similar
to
Q4
if
the current
drawn
from
the supply ex-
ceeds approximately
100
ma.
5 Volt Regulator
A 6.3
volt
zener diode
CR5
is
the reference for
this
regulator.
QB
buffers the voltage a~ross
this
diode
and
drives the chassis
mounted
pass
transistor
AlQ2.
Q9
and
R25
provide the
current
limit
function for
this
supply.
The
limit
point
is
approximate-
ly
500
ma.
-14-
www.SteamPoweredRadio.Com
SECTION
5
ALIGNMENT
AND
TROUBLESHOOTING
5-1
EQUIPMENT
REQUIRED
BUT
NOT
SUPPLIED
l.
RF
Load (50
ohms
-
20
watts
min.)
2.
RF
Wattmeter
(Bird
43
or
equivalent)
3.
FM
Modulation
Monitor
(QEI
671
or
equivalent)
4.
Audio
Generator
(less
than
.1 %
distortion)
5.
Distortion
Analyzer
(Hewlett
Packard
331
or
equivalent)
6.
Dual
Trace
10
MHz
Oscilloscope
(Telequipment
054
or
6
equivalent
7.
110
MHz
Counter
(Stability
better
than
l
part
in
10
)
8.
Signal
Sampler
(-20
to
-30
dB
output)
9.
Spectrum
Analyzer
NOTE:
DO
NOT
ATTEMPT
TROUBLESHOOTING
OR
ALIGNMENT
OF
THIS
UNIT
WITHOUT
ADEQUATE
TOOLS
AND
TEST
EQUIPMENT.
Before
starting
alignment
of
this
unit,
verify
that
three
supply
voltages
are
present
and
correct.
Connect
the
Exciter
to
a
suitable
(50
ohm
-
20
watt)
RF
load
through
the
signal
sampler.
-
5-2
FMO
AND
PHASE
LOCK
ASSEMBLY
ALIGNMENT
l.
AFC
Adjustment
a .
Connect
a
scope
to
test
point
11
L"
. A
ct
j us t A2R47
for
the
greatest
amplitude
linear
5
KHz
sawtooth
obtainable.
b.
Connect
a
scope
to
pin
6
of
A2Ull.
Adjust
trimmer
access-
ible
through
hole
in
FMO
can
until
pin
7 shows a
DC
level.
Either
side
of
lock
will
give
a
sawtooth
signal
whose
frequency
becomes
lower
as
lock
is
approached.
2.
Modulation
Level
Adjustment
a.
Connect
an
FM
Modulation
Monitor
to
the
low
level
output
of
the
signal
sampler.
b.
Connect
a 400
Hz
+10
dBm
signal
to
TBl.
Place
S3
in
MONO
position.
Adjust
A2R31
until
monitor
reads
100%.
C.
Connect
a 400
Hz
4Vpo
(l
.41Vrms)
signal
to
COMP
jack
J2.
Place
S3
in
COMP
pos1tion.
Adjust
A2R65
until
monitor
reads
100%.
3.
Coarse
Frequency
Adjustment.
a.
Connect
a
counter
to
the
low
level
output
of
the
signal
sampler.
-15-
www.SteamPoweredRadio.Com
NOTE:
BE
SURE
OF
THE
ACCURACY
AND
STABILITY
OF
THE
COUNTER.
b.
Remove
all
modulation
from
the Exciter.
If
any
modulation
is
pre-
sent,
it
is
necessary
for
the counter
to
have
a gate time
of
at
least
four seconds in order
to
obtain a
correct
reading.
c. Set
FREQ
ADJ
pot
R2
to
the
center
of
its
range.
d.
Adjust
A2C27
until
Exciter
is
on
frequency.
e.
Vary
FREQ
ADJ
pot
R2
from
end
to end. Frequency should vary app-
roximately+
500
Hz.
Reset Exciter
on
frequency.
5-3
POWER
AMPLIFIER
ALIGNMENT
1. Coarse Alignment
a. Connect a
power
meter capable
of
displaying
25W
to
the
RF
OUT
jack
Jl located
on
the
rear
panel
of
the
unit.
Connect a signal
samp-
ling
probe to the output
of
the
power
meter. Connect a spectrum
analyzer
to
the probe. Connect a
50
ohm
dummy
load
to
the output
of the signal sampling probe.
Be
sure
that
the
power
meter
and
dummy
load are designed
for
use
at
FM
broadcast frequencies.
b.
Apply
power
to
the
unit
and
observe
pilot
lamp
CR2
and
AFC
LOCKED
lamp
DSl.
If
lamp
does
not illuminate
refer
to
FMO
alignment pro-
cedure.
c. Set
PWR
ADJ
control
Rl
full
clockwise. Set the
MULTIMETER
switch
S2
to the
IPA
position.
Set
A3C2
to mid-range.
d. Observe
an
indication
of
IPA
collector
current
on
the multimeter.
Maximize
this
indication
by
adjusting
A2C6
and
A2C7
of
the
A2
board.
e. Set the multimeter switch
to
the
PA
position.
for
a
maximum
reading in
this
position.
f.
Set the multimeter switch
to
the
RF
position.
A3Cl5
for
a
maximum
reading in
this
position.
is
now
complete.
2. Final Alignment
Adjust
A3C7
and
A3C8
Adjust
A3Cl4
and
The
coarse alignment
a. Set
MULTIMETER
switch
S2
to
the
RF
position.
Adjust
A3Cl4
and
A3Cl5
for
maximum
reading
on
the multimeter.
If
the
Power
Amp-
lifier
draws
excessive
current
and
trips
the
power
supply overload
circuitry,
adjust
A3Cl5
clockwise
until
this
condition
is
corrected.
When
this
condition appears, the output
power
is
in excess
of
20
watts. Adjust
A3Cl5
clockwise to reduce the output
power
to
20
watts. Readjust
A3C14
for
a
maximum
reading
on
the multimeter.
-16-
www.SteamPoweredRadio.Com
b.
Adjust
A3C7
and
A3C8
. for a
maximum
reading
on
the
MULTIMETER.
c. Adjust
A3C2
for
stability
as observed
on
the spectrum analyzer
as follows:
Turn
the
PWR
ADJ
control
Rl
to
the
max,
CCW
position.
Adjust
A3C2
for
stability
as observed
on
the spectrum analyzer.
Turn
the
PWR
ADJ
control to the
max.
CW
position.
Adjust
A3C2
if
necessary to
stabilize
the
unit.
5-4
EXCITER-TRANSMITTER
INTERFACE
When
connecting the Exciter to the Transmitter, tuning
of
the
transmitter
input
circuitry
will
be
facilitated
by
the use
of
a
3dB
20watt
pad
and
a
thru-line
wattmeter
between
the Exciter
and
the Transmitter.
If
these de-
vices
are
not
available
reduce the output
power
of
the
exciter
and
tune the
input
of
the
transmitter
until
a
somewhat
reasonable
match
is
obtained.
If
the Transmitter
is
already tuned to
exciter
frequency a "touch
up"
adjust-
ment
should
be
all
that
is
necessary.
If
the
IPA
of
the
transmitter
can
be
mistuned to the point
of
oscillation
be
sure
to
use the
3dB
pad.
It
is
poss-
ible
to
drive
large
amounts
of
power
back
into
the Exciter
from
an
oscillat-
ing
IPA
thereby destroying the output
transistor.
5-5
TROUBLESHOOTING
Refer
to
schematics for
waveform
and
voltage information.
Using
these,
the
theory
of
operation in Section 4
and
the
test
equipment
listed
should allow
a competent engineer to diagnose
most
problems.
If
factory
help
is
required,
it
is
as
close
as your telephone.
In
addition,
do
not attempt replacement
of
components
on
printed
circuit
boards
unless
you
are
familiar
with
this
work. All
PC
boards
can
be
severely
damaged
by
using the
wrong
tools or methods.
Do
not use a soldering iron over
25
watts
or anything
other
than 60/40
ROSIN
core
solder.
Use
a "solder sucker" or "sold-
er
wick" wire
to
remove
a component.
Because the
Power
Supplies are overload
protected,
it
is
possible for a
defect
on
the
A2
or
A3
boards to cause a voltage
to
be
either
missing or
less
than
nominal.
If
a voltage
is
low
or missing
remove
the load
and
see
if
the
volt-
age
returns.
5-6
POWER
TRANSFORMER
WIRING
1. Input Voltage
Change
a.
Change
jumpers
as
shown
on
next page.
-17-
www.SteamPoweredRadio.Com
NOTE:
To
Line
Cord
Primary
Power
XFMR
105-125V
Connection
To
Line
Cord
Primary
Power
XFMR
210-250V
Connection
Refer to Chasis Schematic
for
further
details.
b.
Mark
rear
of
chassis to
show
supply
for
which
unit
is
wired.
2.
Tap
Change
a.
If
Exciter
is
to
be
used
below
to
CRl
instead
of
Yellow
lead.
wer
to approximately
12
watts,
within the
unit.
12
watts ,
connect
Red/Yellow
lead
This change will
limit
output po-
but will reduce heat
dissipation
b.
Change
A4Rl0
from
820
ohm
to 1.5K. This insures
that
the
IPA-PA
supply stays in
regulation
with the reduced input voltage.
c.
Change A4Rl9 from 120
ohm
2
watt
to
68
ohm
2
watt.
This
insures
that
the
+15
volt
supply
stays
in
regulation
,
-18-
www.SteamPoweredRadio.Com
X---TIE
TO
GROUND
FREQ.
MHz
Xl-X2 Al Bl
88. l 0
X
88.3
0
X
88.5
0
88.7
0
X
88.9
0
89. l 0
X
89.3
0 X
89.5
0
89.7
0 X
89.9
0
90. l 0 X
90.3 0 X
90.5 0
90.7 0 X
--
90.9
0
91. l 0 X
91.3 0
X
91. 5 0
91. 7 0 X
91. 9 0
92.l
0 X-
92.3 0
X
92.5 0
92.7 0 X
92
·
.9
0
93.l
0 X
93.3 0 X
93.5 0
93.7 0 X
93.9 0
94. l 0 X
94.3 0 X
94.5 0
94.7 0 X
94.9 0
-
TABLE
5-1
PROGRAM
KEY
0---0PEN
Cl
Dl
A2
X
X
X X
X
X X
X
X
X
X
X
X
X X
X X
X
X
X
X X X
X X X
X X
X
X
X X
X
X
X X
X
X
X
X X X
X X X
X X
X X
X X
X X
X X
X
X
X
X X X
X X X
X X
X X
-19-
*---
SHORT
B2
C2
D2
A3
B3
C3
D3
X X X X
X
X X X
X
X
X X X X
X
X X X
X
X
X
X X X
X X
X
X X
X
X
X X X
X X
x·
X X
X X X X X
X X
X
X X
X X X X X
X X
X X
X
X X X
X
X
X X X X X
X X X X X
X X X X X
X X X X
X
X X
X
X X
X X
X
X X
X X X X X
X X X X X
X X X X
X X X X
X X
X X
X X X X
X X X X
X X X X
X
X
X X
X
X
X X
X X X X
X X X X
X X X X
X X X X
X X X X
X X X X
www.SteamPoweredRadio.Com
FREQ.
MHZ
Xl-X2
Al Bl
Cl
Dl
A2
B2
C2
D2
A3
B3
C3
D3
95. l 0 X X X X X X X
95.3
0 X X X X X X X
95.5
0 X X X X X X
95.7
0 X X X X X X
95.9
0 X X X X X
96. l 0 X X X X X X
96.3
0 X X X X X X X
96.5
0 X X X X X X
96.7
0 X X X X X X
96.9
0 X X X X X
97. l 0 X X X X X X
97.3
0 X X X X X X
97.5
0 X X X X X
97.7
0 X X X X X
97.9
0 X X X X
98. l 0 X X X X X
98.3
0 X X X X X X X X
98.5
0 X X X X X X X
98.7
0 X X X X X X X
-
98.9
0 X X X X X X
99. l X X X X X
0 X X
99.3
0 X X X X X X X
99.5
0 X X X X X X
99.7
0 X X X X X X
99.9
0 X X X X X
l 00. l * X X X X X X X X X X X X
100.3
* X X X X X X X
100.5
* X X X X X X X X X X X
l 00.7 * X X X X X X X X X X
·100.9 * X X X X X X X X X X X
l 01. l * X X X X X X X X X X X
l 01.3 * X X X X X X X X X X
l 01.5 * X X X X X X X X X X
101.7 * X X X X X X X X X
l 01.9 * X X X X X X X X X X
l 02. l * X X X X X X X X X X X
102.3
* X X X X X X X X X X
l 02. 5 * X X X X X X X X X X
102.7
*
X
X X X X X X X X
l 02.9 * X X X X X
X
X
X
X X
-
-20-
Other QEI Recording Equipment manuals
