Lafayette STARFLITE KT-390 User manual

FR - D2O
assembly
manual
STARFLITE
90 WATT TRANSMITTER

EE
6 vi v3 7
[x3}—0 BCLE 6CL6 6146 ON TER
OSCILLATOR a DRIVER | FINAL AMPLIFIER
(x5}—_S ) . L
v4 V5
|2AXT 6DE7
SPEECH AMPLIFIER MOOULATOR
BLOCK DIAGRAM
SUPPLY
HEATER
CIRCUIT DESCRIPTION
While reading the circuit description, refer to both the Block and Schematic diagrams,
OSCILLATOR
The oscillator stage, V1, functions as a modified Pierce crystal oscillator, The crystal selector
switch SW-1] is used to select the desired crystal, When VFO operation is desired, the VFO output is
connected to the VFO INPUT jack and V! then operates as a buffer stage. The oscillator may be
operated at the fundamental frequency of either an 80 or 40 meter crystal, The plate circuit is
untuned for 80 meter operation, coil L1 having no effect in the circuit on this band, The plate circuit
ie alug tuned by coil Ll for operation on 49 through 10 meters,
The output of Vl is coupled to y2 (the driver stage) through capacitor C4,
DRIVER
The driver tube, V2, is operated as a class C amplifier, Its plate circuit is tuned to the desired op-
erating frequency by coil L3 (or portions thereof, selected by Band Switch SW-Za) and variable capacitor
C8 (DRIVE TUNE). This stage operates straight through on 80 and 40 meters, as a doubler on 20
leas sn il n —o
Tt tore, =
The DRIVE LEVEL control, R5, varies the screen voltage of Y2 and thus controls the output (drive},
which is coupled to the prid of the final amplifier through capacitor C1z,
FINAL AMPLIFIER
Final amplifier tube V3 operates straight-through on all bands as a shunt-fed, neutralized amplifier,
The tank circuit is made up of C20 (FINAL TUNING), Lé4 (or portions thereof, selected by Band Switch
SW-2b}, and C22 (FINAL LOADING), C22 consists of three 450 ppf parallelled sections to eliminate the
need for switching fixed capacity into or out of the circuit when changing bands, (C21 is added to the
tank circyit on 80 meters to maintain a good L-C ratio on this band,
The output ie fed through a 3-section low-pass filter with a cut-off point of approximately 34MC, ef-
fectively suppressing RF energy above this frequency. The output should be connected ta a 50-75 ohm
unbalanced line,
Grid or Plate current of the final amplifier is read by proper positioning of switch SW-4 (METER switch).
In the "Grid" position, the meter reads the voltage developed across resistor Ri0, and thus, in effect,
measures the grid current passing through this resistor,
In the "Plate" position, the meter reada the voltage developed acrose the resistor R13, and thus meas-
ures the current drawn through this resistor, Although cathode current is actually the combined grid,
acreen, and plate current, the reading may be taken as a true indication of plate current, The error
cauged by the addition of grid and screen current is very ammall and on the legal side,

yt &
SPEECH AMPLIFIER
V4, atwin trinde, operates as
second triode section is couple
MODULATOR
The
modulator
tube
V5
consists
of
two
dissimilar
triodes,
one
with
a
power
rating
of
1.5
watta
and
the
other
7
watts.
The
output
of
the
lower
power
triode
ia
coupled
directly
to
the
grid
of
the
higher
power
triode
which
is
eactually
the
modulator,
The
cathode
of
the
modulator
section
is
coupled
to
the
screen
prid
of
V3
(final
amplifier)
through
R25
and
C30.
The
bias
on
V5
1s
so
arranged
that,
with
no
audio
mput
signal,
conduction
of
the
tube
is
limited
(low),
This
allows
the
screen
voltage
of
the
final
amplifier
V3
to
remain
at
a
low
value,
thus
reducing
the
plate
current
of
V3
to
a
low
resting
state,
When
an
audio
signal
is
applied
to
¥5,
conduction
in
the
modulator
section
increases,
raising
the
screen
voltage
of
¥3,
This
causes
an
increase
in
the
plate
current
of
V3
with
modulation
producing
a
controlled-carrier
effect,
“iy
Sy
GRID BLOCK KEYING
ry
ollowing
way:
With
the
key
plug
inserted
and
in
the
key
up
position,
a
high
bias
voltage
(several
times
the
normal
grid
bias}
is
placed
on
the
grids
of
tubes
V1,
VZ
and
V3.
This
cuts
these
tubes
off
and
there
is
no
transmitter
output.
eving ig achievedi
Keying af GOT YOU Li
In
the
key
down
position,
R&S
is
shorted,
removing
the
high
bias
voltage
from
VI
and
¥2,
Also,
the
bias
voltage
to
V3
is
reduced
to
a
normal
operating
value
through
RY,
The
amount
of
fixed
bias
on
V3
is
sufficient
to
protect
the
tube
should
the
drive
be
accidentally
removed.
The
values
of
RA
and
C2
were
chosen
to
provide
the
most
desirable
waveform
on
CW.
a
woe
bees
Vi Vv V3
RI
|
ws
Ri
—
&
=
—-130V
:
GRID
BLOCK
KEYING
voy
,
POWER SHPPLY
The
B+
supply
is
derived
from
four
silicon
diodes
(D2,
D3, D4, D5)
ina
voltage
doubler
circuit,
Filtering
is
provided
by
C34,
C35,
C36,
and
resistora
R28,
R29.
The
bias
voltage
for
grid
blook
keying
is
developed
by
silicon
diode
D-1
in
a
half-wave
xrectifiar
cir-
cuit,
Filtering
is
provided
by
C33
and
R27,
~
cd +
A
separate
winding
provides
6,3
volts
at
4
amps
at
the
accessory
power
socket
for,
YFO
flaments
or
other
accessory
equipment,
eof
Os

OPERATION
An Amateur Radio Operator and Station License must be obtained before placing this transmitter on
the air, If you require any information regarding licensing and amateur frequency allocations, contact
the Federal Communications Commission PCr. ae thse Asssvizan Badin Delta
Ths WVOMTLTTUMLCOTONe WOTYc ion pe OF Pe GEC PIiCah aa wlaay League {ARRL).
ANTENNAS
The pi network output circuit of the KT-390 will match pure resistive loadsa of 50 to 75 ohms, A simple
"dipole" antenna, constructed so that its lenpth is a half wavelength at the frequency of operation, of«
fers a good match for this transmitter, Other antennas falling into the 50-75 ohm range are beams,
verticals, and trapped antennas Useful information on n this subject can be found in the Radio Ama-
CRYSTAL OPERATION
Recommended crystals for operation on the various bands are as follows:
BAND FUNDAMENTAL CRYSTALS
60 meters 160 or 80 meter crystals
40 meters 80 or 40 meter crystals
20 meters 80 or 40 meter crystals
15 metera 40 meter crystals
10 meters 40 meter crystals
Pin spacing 0,486" Pin size .093 dia,
NOVICE OPERATION
Novice operation is restricted to the following frequencies,
BAND FREQUENCY ALLOCATION
80 meters 3700 - 3750KC
40 meters 7150 -7200KC
15 meters 21, 100 ~ 21, 250KC
Novice power input is limited to 75 watts, In the operating instructions, the final amplifier is loaded
to 120 ma for novice operation (as opposed to 150 ma for regular operation), This keeps power input
within the present novice power limitation,
CAUTION
Be sure to check the latest FCC regulations regarding amateur frequency allocations and power input
requirements, When ordering crystals, be sure to stay well within the assigned bands of frequencies
or a violation will result,
ACCESSORY SOCKET
The accessory socket at the rear of the transmitter supplies the following:
6,3V AC at 4 amps Pin 7
300V DC at 50 ma Pin 3
*~-50¥ DC Bias Pin 8
Pin 5
110V AC (for Relay) (Pin 6
Ground Pin 1
This bias voltage has been made available for grid block keying of a VFO, Slight modification of the
VFO may be necessary in order to make use of this voltage, Information on any changes necessary
for grid block keying of your VFO can usually be obtained from the manufacturer,

NOTE: When using a VFO with an output impedance lower than 47K (this applies to link-coupied types as
well), it will be necessary to add a decoupling capacitor in series with the VFO input to the transmitter,
18.
OPERATING INSTRUCTIONS
FOR “AM” OR “CW”
Plug the line cord into an AC outlet, Make sure the antenna is connected and that desired crystals
(or VFO} are installed,
Place the MODE ewitch in the "standby" position, -
Set DRIVE LEVEL and DRIVE TUNE to approximately 1, L fo ° “4
Using the CRYSTAL SWITCH, select desired crystal (or VFO).
Select the desired BAND,
Set the FINAL TUNING control to the panel marking for the band being used,
Set the FINAL LOADING control fully counter-clockwise,
Set the METER switch to "Grid",
Set the MODE switch to "'Tune''!,
Adjuet DRIVE TUNE for maximum grid reading on the meter,
Adjust DRIVE LEVEL for 2,5 ma grid current,
Change METER switch to the ''Plate'" position.
Set MODE switch to "'AM'",
Adjust FINAL TUNING for minimum plate current reading (dip).
Set MODE switch to CW,
mall steps, adjusting the FINAL TUNING for
mi =
munimum pla fa currant fdin 4 fter each ston
120 ma for NOVICE operation,
150 ma for REGULAR operation,
Set METER awitch to "Grid", Re-adjust DRIVE TUNE for a maximum grid reading, then re-set
DRIVE LEVEL for 2,5 ma,
Return METER switch to "'Plate'! and the MODE switch to 'STBY'",
FOR CW OPERATION
1
2
Insert key plug in KEY jack,
To transmit, switch MODE to "CW" and proceed,
FOR AM OPERATION
3.
lf inserted, remove key plug (or close the shorting bar if the key is so equipped),
Attach microphone to MIKE connector,
To transmit, switch MODE to "AM" and proceed,

OPERATING NOTES
1,
Operating
the
transmitter
without
a
crystal
(or
VFO),
a
proper
antenna
or
dummy
load
will
result
in
component
failure.
2,
Operating
the
transmitter
with
the
final
amplifier
not
tuned
to
resonance
(minimum
plate
current)
may
damage
the
final
amplifier
tube,
3.
Never
switch
directly
from
OFF
to
the
AM
or
CW
positions
or
the
final
amplifier
tube
will
be
damaged,
Always
switch
to
the
"STBY"
position
first,
leaving
the
mode
switch
in
thia
position
for
at
least
60
seconds
before
attempting
to
operate
the
transmitter.
This
will
allow
the
tubes
to
reach
normal
operating
temperatures.
4,
If
you
change
your
operating
frequency
by
more
than
a
few
kilocycles,
it
may
be
necea sary
to
re-
tune
the
driver
and
final
amplifier
stages,
-
5.
Never
cover
the
perforations
in
the
top
of
the
cover
or
ventilation
will
be
restricted,
Failure
to
observe
this
precaution
will
result
in
sharply
reduced
component
and
tube
life,
IN THE EVENT OF DIFFICULTY
A,
If
all
of
the
tubes
remain
unlit
when
the
transmitter
is
turned
on,
or
if
they
suddenly
go
off,
check
to
sce
that
the
fuse
is
intact.
Uf
it
is
not,
replace
it
with
one
of
the
same
value
(see
parts
list}.
Should
the
fuse
blow
again,
a
short
or
a
component
failure
must
be
suspected,
B., Carefully re-check all wiring and valuea of components inserted against the inatructions. If you
have
not
already
done
ao,
trace
each
lead
and
component
in
the
pictoriala
with
a
colored
pencil.
It is frequently helpful to have a friend check your work with you as there is a tendency for the
constructor to repeat his errors,
C. Inspect all solder connections carefully. A large number of kits returned for repair haye been
found
defective
due
to
poox
solder
connections,
Therefore,
any
doubtful
connections
should
be
re-
heated to make gure they are correctly soldered,
BD, Check for small piecea of solder or wire which may have fallen into the chassis, Make sure that
the use of excess solder has not caused a short between adjacent terminals or nearby wiring, par-
ticularly on tube sockets and switch terminala,
E.
Check
all
tubes
with
a
tube
tester,
or
by
substitution
with
tubes
of
the
same
type
and
known
to
be
good,
F,
A
resistance
chart
has
been
included
as
an
aid
in
locating
defective
componenta
and
to
permit
a
careful
stage-by-stage
check
of
the
unit,
If
any
of
the
readings
obtained
differ
widely
from
those
provided
in
the
chart,
recheck
that
part
of
the
circuit
involved
carefully,
If
the
wiring
and
con-
nections
are
correct,
component
failure
must
be
euapected,
G,
If
you
are
still
unable
to
locate
the
trouble
and
a
vacuum-tube
voltmeter
is
available,
check
the
voltage
readings,
referring
to
the
voltage
chart.
A
variation
of
+15%
may
be
considered
normal,
If
any
voltage
is
incorrect,
recheck
that
part
of
the
circuit
involved
carefully.
If
the
wiring
and
connections
have
already
been
checked
and
found
correct,
the
trouble
will
probably
be
due
to
a
de-
fective
part
(tube,
capacitor,
resistor,
etc.),
CAUTION:
EXERCISE
GREAT
CARE
WHEN
MAKING
ANY
CHECKS
WITH
THE
UNIT
TURNED
ON,
lf
there
are
obvious
signs
of
a
short
circuit
(components
becoming
discolored
or
amoking)
do
not
attempt
to
make
yoltage
checks,
Switch
the
unit
off
and
remove
the
AC
plug
until
the
short
circuit
has
been
lo-
cated
and
the
trouble
corrected,
Parts
found
defective
may
be
returned
(postpaid)
to
ue
for
replacement,
[If
they
are
covered
by
the
re-
placement
warranty,
new
parte
will
be
sent
to
you
at
no
charge.
AJ]
packages
should
be
addressed
to
the Kit
Adjustment
Division,

Part No,
12-219
12-205
12-193
12-194
12-196
12-220
12-197
12-198
12-199
12-190
12-2
12-191
12-34
12-22
12-192
12-79
12-200
12-201
12-202
12-203
12-204
12-82
12-11
23-37
23-38
23-39
23-40
23-41
23-42
235-32
22 22
os -F
23-43
23-34
15-43
14-46
14-47
14-45
14-17C
20-23
20-22
20-47
20-74
20-20
20-311
20-312
20-313
20-305
20-314
20-317
20-43
Circuit Designation
C23/R16
C18
C36a, b
C34, 35
C25
C33a, b
cs
C20
C22
C2,5,6,7,9, 14, 13, 14,
15, 16, 17, 37, 38, 39
cl
c4
C3, 12, 29
C2t
cal
c24
C40, 43
C41, 42
c19
clo
C26, 28
C31, 32
C30
Description
CAPACITORS
Tube-~R-Kap (combined 560K ohms /100 ppl}
0,003 pf 1o00¥y feed-through
40-40 pf 450Y electrolytic
30 pf 450V electrolytic (with insulating covering)
10 pf 350V electrolytic (with insulating covering)
10-10 pf 150V electrolytic (with insulating covering)
25 wpf variable (DRIVE TUNE)
140 put variable (FINAL TUNING}
3 gang variable, 450 put per section(FINAL LOADING)
0,005 pf 500V 20% ceramic disc
0,001 pf 500y 10% ceramic disc
50 ppf S00V 10% ceramic disc
100 ppf 500V 10% (N750} ceramic disc
470 ppf 500V 10% ceramic disc
68 pf 3KV 10% ceramic disc
0,002 pf 500V 10% (may be marked 2000)
47 pi 300V 10% molded mica
180 ppt 300V 10% molded mica
0,001 pf 2000V 20% molded mica (marked 12-202)
120 pp£ 1500V 20% molded mica (marked 12-203)
0.005 pf 400V 20% molded paper
0,01 pf 600V 20% molded paper
0,05 pi 400V 20% molded paper
COILS, CHOKES, TRANSFORMERS
RF choke 1 mh
RF choke 1,1 mh
RF choke .4 ph
.32 ph low-pass filter coil (yellow dot)
-44 ph low-pass filter coil (green dot)
.5 ph low-pass filter coil (blue dot)
40 meter oscillator coil
Dvi-er sinte 2631
afFiyeor peatc cols
Parasitic choke
Pi-net tank coil
Power transformer
SWITCHES
5-position 1 section rotary (MODE switch)
6-position 1 section rotary (CRYSTAL switch)
5-position 2 section rotary (BAND switch}
DPDT slide switch (METER)
TERMINAL POSTS
3-lug
4-lug
3-lug
1-lug
2-lug
4-lug
5-lug
5-lug
3-lug
3-lug
Z-lug
2-lug
Quantity
A a —
Bw Nh ee Nw ON ee Re Re te Oe
ee ee ee | lll el ee oo oe oe A 38 ed
De a el

Part No,
19-46
19-30
19-45
19-3
20-282
19-25
20-228
26-51
26-38
26-1
26-52
17-23
17-24
10-152
1o0-151
io- 150
10-149
10-148
10-147
10-146
10-145
16-144
10-143
10-142
19-141
27-5
20-173
20-304
20-290
an an
ey he
20-310
20-309
20-198
20-11
20-315
20-318
20-215
20-175
26-12
20-210
20-75
20-33
22-150
22-90
22-147
18-70
18-69
22-10
22-11
22-42
Circuit Designation
pantalla paeeln nana nua
ys
yil,v2
4
V5
D2, 3, 4,5
D1
Deacription
SOCKETS, JACKS, CONNECTORS
Octal tube socket
Noval tube socket
Crystal socket
RGA phono jack (VFO input)
Coaxial connector (RF OUTPUT)
Closed-circuit jack (KEY jack), with hardware
Mike connector (MIKE input), with hardware
TUBES AND DIODES
cou oar
6146 tube
6CL6 tube
1ZAX7 tube
6DE7 tube
Silicon diode (marked 1723)
Silicon diode (marked 1724)
SHEET METAL PARTS
Cover plate
Shield bracket
Shield bracket
Crystal socket bracket
Final amplifier shield (rear)
Final amplifier shield (front)
Center shield
Low-pass filter housing
Escutcheon
Cover
Bottom plate
Chassis
MISCELLANEOUS
O-Ll ima meter
Tube shield
Tube shield
Ceramic plate cap
Ceramic standoff terminal
Pitot light socket
Standoff insulator
Pilot lamp
Pilot lamp jewel (red)
Foot (Polyethylene, gray)
AC line cord
Strain relief
Fuse holder
3 amp fuse, 3AG
1/4" grommet
Electrolytic mounting wafer
L/2'' grommet
SHAFTS, BUSHINGS, KNOBS
1/4'' diameter shaft
3/8"
panel
bushing
for
1/4"
shaft
(with
hex
nut}
Shaft coupler
Knobs, small
Knobs, large
HARDWARE
4-40 x 1/4” machine screw
6-32 x 1/4" machine screw
8-32 % 3/8" machine screw
meee oe
ee whe eee ee ee Ne Se ee
BUD oe
34
15
Quantity |
4
2 |
23
ae
lL 4
1
1
l
boy
2
1
l
4
1

Part No. Circuit Designation Description Quantity
22-149 4-40 x 7/8" machine screw 1
22-66 2-56 x 1/Z" machine screw 5
22-146 6-32 x 3/16" machine screw 5
22~ 144 6-32 x 3-3/4" bolt 1
22-116 #4 x 1/4" sheet metal screw 10
22-152 #8 x 3/8" sheet metal screw (nickel plated) 4
22-92 4-40 x 3/8" machine screw 1
22-27 8-32 x 1/4" machine screw 4
22-93 #68 x 3/8" sheet metal screw (hex head) 20
22-16 #4 internal tooth lockwasher 36
22-28 #8 internal tooth lockwasher 1zZ
22-122 #2 internal tooth lockwasher 5
22-142
#8
flat
steel
washer
2
22-154 #6 split lockwasher 3
22-2) 3/8" internal tooth lockwasher 7
22-143 Fiber washer 1
22-17 #6 internal tooth lockwasher 28
22-140 Cork washer 3
22-14 4-40 hex nut 36
22-46 2-56 hex nut 5
22-26 8-32 hex nut 8
22-15 6-32 hex nut 28
22-145 5/16" hex nut (for C18) 1
22-20 3/8" hex nut &
20-24 #6 solder lug i
22-151 6-32 x 7/16" spade lug 8
20-100 Double solder lug z
22-106 Solder lug 4
22-141 Thumbscrew, 8-32 x 1/2" 1
20-83 #8 solder lug 1
22-156 6-32 x 1/4" spade lug 2
WIRE AND SLEEVING
21-15 #22 Black lead 24"
21-11 #22 Yellow lead 60"
21-69 fee Gray lead 561
21-25 #22 Red/White lead 198"
21-13 #22 White lead TZ
21-14 #22 Blue lead 69"
21-87 #18 Yellow lead 60"
21-86 #20 Bare wire 4g"
21-18 Yellow, cotton varnished sleeving 30"
21-19 Black, vinyl sleeving 12"
21-868 #22 Red lead, heavy insulation 30"
20-1044 Solder, 15-f£, roll !
NOTE, To test the transmitter after completion, it wil] be necessary to construct a dummy load. You
will need a coaxial connector (PiL-259 or equivalent), a 75 watt light buib, and about 12 inches
of #16 bare wire, You may wish to purchase these parts now to avoid delay after construction,
IMPORTANT: For convenience in packing, the AC power transformer has been temporarily mounted
on the main chassis, Please remove this transformer before beginning construction, Instructions for
its installation will be provided at the propar time,

Part No,
13-272
13-273
13-217
13-267
13-215
13-72
13-269
13-1
13-50
12_A0
ae EG
13-51
13-280
13-45
13-4
13-3
13-226
13-75
13-118
13-99
13-19
13-281
13-144
11-57
11-58
Circuit Designation
na
aA
R9, 15, 20
Rll
R18, 19
R14
R17
R24
R23
R27
"wt
R13
Rl2
RLO
R22
RS
R21
PARTS LIST
Description
RESISTORS
TEN shms &
25K ohms 30 watt, wire-~wound (center-tapped}
15K ohms 2 watt (brown-green-orange-silver)
12K ohms 2 watt (brown-red-orange-silver)
1.5K ohms 2 watt (brown-green-red-silver)
10K ohms 2 watt (brown-black-orange-silver)
6,8K ohms 2 watt (blue-gray-red-silver)
100K ohms 1/2 watt (brown-black-yellow-silver)
33K ohms 1/2 watt (orange-orange -orange -silver)
10K vlims 1/2 wait (brown-biack-orange -silver)
4,7K ohma 1/2 watt (yellow-viclet-red-silver)
18K ohms 1 watt (brown-gray-orange-silver)
470K ohms 1/2 watt (yellow-violet-yellow-silyer)
47K ohms 1/2 watt (yellow-violet-orange-silver)
2,2 megohm 1/2 watt (red-red-preen-silver)
33K ohms 1 watt (orange -orange-orange-silvyer)
1.5 megohm 1/2 watt (brown-green-green-silyer}
330 ohms 1/2 watt (orange-orange-brawn-silver}j
10 ohms 1/2 watt (brown-black-black-silver)
2.2K ohms 1/2 watt (red-red-red-silver)
620 ohms 1/2 watt 5% (blue-red-brown-gold)
22 megohm 1/2 watt (red-red-blue-silver)
25K ohms 4 watt wire-wound (DRIVE LEVEL)
100K ohms 1/4 watt potentiometer
Oe |
tt 22 We
Quantity
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