Kenwood TL-911 User manual

Ample
2KW
PEP
input
provides
high
power
operation
in
SSB.
i
x
class
AB
grounded-grid
configuration
with
the
regulated
screen
grid
voltage
is
employed
to
assure
stable,
distortion-free
SSB
transmission.
‘The
linear
switch
can
be
set
to
CW
for
additional
_
safety
in
CW
(A1)
operation,
=
is
re
ae
|
ree
An
overcurrent
detection
type
protection
circuit
is
added
to
prevent
heat
trouble
caused
by
abnormal
operations
and
to
assure
safe
tuning,
which
would
be
difficult
with
the
TV-application
~ tubes.
The
plate
currents
in
the
power
amplifier
tubes
can
be
monitored
individually
to
facilitate
determining
which
tube
is
defective
when
they
develop
flashing,
low-emission
trouble,
etc.
A
dynamic
balance
circuit
is
employed
to
make
power
sharing
uniform
among
the
power
amplifier
tubes.
This
enables
all
power
tubes
to
serve
with
full
efficiency
and
safety.
|
The
ALC
circuit
is
a
dual
type
which
centrols
both
Igi
and
Ig2
for
quality
transmission
over
an
extended
dynamic
range.
| |
An
SWR
meter
is
provided
for
quick
matching
to
the
antenna.
A
final
tube
box
with
efficient
heat
radiation
and
a
large,
powerful
cooling
fan
(with
a
6-vane)
are
employed
to
double
the
life
of
power
tubes.
TL-911
is
designed
as
a
desk
top
type,
the
same
construction
as
TS-515
transceiver
so
that
they
can
be
put
together
on
a
space-limited
table.
:
Switching
between
exciter
and
linear
amplifier
operations
is
simple
and
accomplished
by
switching
an
antenna-through
relay
by
means
of
the
linear
switch.
CONTENTS
ETERNAL
VIEW
ssc
ve
seecc
dad
sitetenaesscete
reece
ee
teats
3
TOP
CHASSIS
VIEW.......
eee
cee
eee
eee
e
ene
eneete
sen
enaees
:
4
BOTTOM
CHASSIS
VIEW
.....
0.
cece
cece
eee
erent
teen
tees
5
CIRCUIT
DESCRIPTION
.....
0.0202
cece
eee
cert
eee
eee
eee
t
ents
6~8
TROUBLESHOOTING
.........0
cece
ec
ee
ee
eee
ete
teen
eenes
neat
9~
10
CONNECTING
REMOTE
CABLE
.........--+++++::
ee
ree
11
ADJUSTMENT.
oouasulawiseugs
ce
die
yyeuaeen
ude
aaa
te
aes
12~
15
VOLTAGE
MEASUREMENTS
OF
TUBES
AND
TRANSISTORS
........---
—
16
PARTS
LIST
.....-
Se
Te
ee
ere
ee
ere
17
~
21
PC
BOARD
cctees
do
tten
sd
oder
etewesw
bbe
ee
noes
seeeeaeens
ene,
92.23
SCHEMATIC
DIAGRAM
......-.--ecseeceeeeeeeeeeeees
ee
SPECIFICATIONS
&
COLOR
CODE
....
see
ence
ee
eee
eee
eee
ene
24

Knob
Meter (B31-0114-05)-— (K21-0226-03)
Knob
(K21-0210-03) .
Toggle switch __ Knob
(S44-2009-00) (K21-0213-04)
Panel
(A20-0466-02)
> Lampholder Toggle switch
(E15-0040-00)~~ (S44-2009-00)
. Name plate
VARA
(B40-0425-04)
2024-00). Ba a eos nm aa ante che te Msi ees be Receptacle type M
VR6 (RO3-2024-00) (ar 7 (eomeaTieon)
Fan
(T40-0002-00)———_——
ae
|
=
ee
oe
3
a
Case
(A01-0147-01)
ABoicaves spcxseatc /
sooo sassac eed faa eaabon otc aStaraleioeaicissonesnes
LEALLE HORI IY
WKS 28340x
Receptacle,
type
M
Our
ane
1
Ho)
(E04-0115-05)
|
e.2.
i
Fuse
holder
~~~
VR5
(RO3-3048-00)—
|
(E15-0041-00)
Oe
Se
ae
eeeenene
anes
Nut
(M14-0053-00)

C44
(C90-0095-00)
C43
(C90-0094-00)
C28 (CE62AD2H 470 x 2)
C29 (CE62AD2H 470 x 2) «
V2 (6LQ6)
T1 (LO9-0095-00)
awn V3 (6LQO6)
VR8 (R12-3001-05)
_——- Fan (T40-0002-00)
VR7 (R12-3001-05) ——
VR6
(1.P.L
SET)
__
cttw
A
LBL
OG)
(R12-3001-05)
Pana
VR5 (R12-3001-05) ——
a
VR4
(R12-3001-05)-————
|
|
—
V5
(6L.Q6)
VR3
(RO3-2023-00)
—————!_
ca
re
4
Pr}
|
be
vars
(R03-2023-00)
ae a (| O45 296-00)
VA Wie sae 6.0 yo) Sewers Oe ee, ! : : : ? | Pian he Seem S1 (S19-2003-00)
V6 (6CWS5) a ae Se ee Pare eI eae eee _! : Bsasacesutitrcanieeasapnimneatceacencrnanoasasmnietsecsaoavanisicn meena \/ | (6LQ6)

BOTTOM CHASSIS VIEW
VR5 (RO3-3048-00)
Fan (T40-0002-00)
VR6 (RO3-2024-00)
L10 (L33-0156-00)
Receptacle type M
(E04-011 5-05)
SBS 4D LRES4 FRF442.dTK5
Cbetrs re ssees
TCS (CO5-0029-05) ==
S5 (SO01-1008-00) -
R1,
R3,
R5,
R7,
oo
(RW
98G3D1004)
S4 (S01-1007-00) ™
VR1
(R12-3031-00)
=
RL2 (S51-301 0-00)
C29 (CE62AD2H 470 x 2)
.C44 (C90-0095-00)
eee US socket
"(EO01-0801-05)
-Nut (N14-0053-00)
————— T 1 (LO9-0095-00)
Fuse holder
(E15-0041-00)
—————— $2 (S44-2009-00)
RECTIFIER
UNIT
=~ S3 (S45-2001-09)
—-C28 (CE62AD2H 470 x 2)
ome C27 (CE62AD2H 470 x 2)
-VC2 (CO1-016 1-00)

CIRCUIT DESCRIPTION
O OUTLINE
TL-911 linear amplifier circuit is shown in the block diagram of Fig. 1.
The hybrid type amplifier employs 6 vacuum tubes, 3 transistors, 27
diodes, and 1 thyristor. The unitized sections are so arranged that each
unit performs a different function of the amplifier, thus permitting the
final amplifier section to be completely shielded, and the rectifier and
control units independently mounted on the printed circuit boards, etc.
O FINAL POWER AMPLIFIER SECTION
The five 6LQ6 tubes are enclosed in a shielded box containing a powertul
cooling fan. The tube operation is Class AB for SSB and Class C for CW in
a grounded-grid configuration. The required bias switching is accomplished
by means of the LINEAR ON switch. The screen grid voltage to obtained
from a regulated power supply, thus assuring freedom from distortion. In
addition, a dynamic balance circuit which maintains uniform dynamic
characteristics among the power tubes, a dual type ALC circuit for
improved linearity, and an SWR meter circuit are included.
O POWER SUPPLY SECTION
The individual supply voltages from a large power transformer having a
current capacity more than actually required are rectified by rectifier unit
X43-1010-00. The high voltage for the tube plates is obtained from a
bridge rectifier composed of 8 diodes (10D 10); voltage for the screen grids,
bias circuit and relays are supplied by 10D4 and 10D1.
O OPERATION OF PROTECTION CIRCUIT
109 resistors R1, R3, R5, R7, and RY are inserted into the cathode of
each power tube. When current flows through the cathodes, the resistors
develop voltages, which are fed to the protection circuit through the diode
matrix. Operation of the protection circuit, therefore, is determined by
the cathode current.
The protection circuit is designed to operate when a cathode current of
240 mA continues for 20 seconds or more, or 400 mA or more flows
instantaneously through a power tube.
If a 240 mA current flows through the cathode of one of the power tubes,
a voltage (2.4 V) develops across the cathode and is applied to the input of
the protection circuit to increase the potential across capacitor C16
(220uF). When this voltage increases to 1.2 V, it causes transistor Q3 to
produce approximately 0.7 V across the emitter, which turns the thyristor
on.
The thyristor turn-on results in actuation of relay RL1 connected to the
collector of the transistor. Relay RL1 in turn removes the supply from
relay RL2, which then supplies high negative voltages to the screen and
control grids of the power tubes to cut the tubes off. The relay, at the
same time, lights the protection lamp. Under this condition, the antenna
output is automatically switched to exciter output. This operation is
shown in Fig. 2.
When 400 mA or greater flows through a tube, the thyristor is turned on
by the collector current of transistor Q2. The 400 mA causes the tube to
develop 4 V across the cathode, and the voltage is applied to the emitter of
Q2 through the diode matrix. This voltage at the emitter, however, is
ry a on Te on
the transistor is adjusted to a base voltage of 3.0 V, the transistor develops

CIRCUIT DESCRIPTION
0.7
V
across
the
base-emitter
junction
—
the
same
level
as
produced
by
the
240
mA
fault
current.
Thus,
the
thyristor
is
turned
on
by
this
voltage
to
energize
relay
RL1,
and
protect
the
power
tubes.
To
reset
the
protection
circuit,
shift
the
exciter
stand-by
switch
to
the
receive
mode
or
turn
the
LINEAR
ON
switch
off.
This
procedure
is
necessary
-since
relay
RL2
has
been
self-heid
by
“make”
contacts
since
operation
of
relay
RL1,
The
thyristor
however
has
been
automatically
reset.
Fig.
3
shows
the
operating
characteristics
of
the
protection
circuit.
Power
Amp.
ANT
Detector
Switching ~~~.
Regulated 70V
Rectifier X43-1010-00
P.T
po
Linear ON
a
4 '
1 4g |
1 t
I t
Remote STBY SW
FIG.1 BLOCK DIAGRAM

CIRCUIT DESCRIPTION
RL1~ 1
contact RL2 RL2~2
resets
Thyristor D10
short-circuited Thyristor, off
:
and
cathode
Thyristor,
>
RL1
Make
contact
on
operates
RL1
held
by
exciter
stand-by
switch
RL1~ 6LO6 screen receives
—115V block bias
RLi~4 Protect lamp lights
6LO6 screen receives
between anode
C16 time-constant circuit
FIG.2 OPERATION OF PROTECTION CIRCUIT
VR MAX
100
80
60
VR CENTER
40
20
0
1..5
2
2.5
3
3.5
4
——»
Cathode
voltage
(V)
(50
200
250 300
350
400
———>
Power
tube
current
(mA)
FIG.3 PROTECTOR CHARACTERISTICS

TROUBLE SHOOTING
CAUSE AND CORRECTIVE ACTION
(a)
Confirm
that
remote
calbe
is
connected
to
exciter.
External
stand-by
circuit
is
inserted
in
series
with
TL-911
linear-on
switch.
Linear
amplifier,
therefore,
will
not
operate
by
merely
turning
linear-on
switch
on.
:
Linear
amplifier
is
set
to
transmit
mode
by
connecting
remote
cable
to
exciter,
turning
linear-on
switch
on,
and
exciter
stand-by
switch
to
transmit
mode:
(b)
Is
remote
cable
properly
connected
between
exciter
and
{linear
amplifier?
(Accessory
remote
cable
is
for
TS-515
or
TS-510.
For
use
with
other
exciters,
change
pin
connections,
referring
to
CONNECTIONS
OF
REMOTE CABLE on page 11.)
Confirm
that
voltage
is
on
in
relay
circuit.
TROUBLE
(1)
Linear
amplifier
does
not
operate
in
transmit
mode.
(2)
Output
meter
does
not
(a)
SWR
SEN
knob
on
panel
is
in
fully
counterclockwise
position,
or
deflect.
meter
switch
is
not
in
FWD
position.
(SWR
meter
sensitivity
is
increased
by
turning
SWR
SEN
knob
in
the
clockwise
direction.)
(b)
SWR
detection
circuit
is
inserted
into
coaxial
cable
connecting
relay
RL2
and
antenna
connector.
Confirm
that
the
circuit
is
rectifying
RF
voltage.
;
Also check meter switch circuit.
(3)
Overcurrent
protection
circuit
does
not
operate.
(a)
Protection
circuit
is
turned
off
since
PRO
TIME
knob
on
Fear
of
set
is
set
in
the
fully
counterclockwise
direction,
Note:
This
knob
should
not
be
adjusted
in
normal
operation.
Power
tubes
may
be
damaged
if
transmission
is
continued
with
protection
circuit
off.
(b)
Confirm
that
the
protection
circuit
is
powered.
(The
voltage
should
be
approximately
DC
15
V
at
pin
28
of
X53-1000-00.)
(c)
Protection
will
start
only
after
an
extended
period
at
a
plate
current
of
around
150
mA.
This,
however,
is
not
a
trouble
but
is
due
to
the
operating
characteristic
of
the
protection
circuit.
See
Fig.
3.
(a)
Confirm
that
PRO
TIME
knob,
on
the
rear,
is
set
to
proper
operation
time.
(Refer
to
ALIGNMENT
for
the
time
adjustment.)
(b)
Rated
exciter
input
to
TL-911
is
100
W.
lf
driven
by
more
than
100
W,
protection
will
trip
more
quickly
than
rated
due
to
increase
in
Ip.
See
Fig.
3.
Protection
will
trip
quickly
if
transmission
is
continued
at
an
Ip
of
around
300
mA.
This,
however,
reduces
the
life
of
the
power
tubes,
and
drive
should
be
reduced.
(c)
If
linear
amp
tank
circuit
is
improperly
adjusted,
plate
dissipation
will
be
greater
under
this
condition.
Ip
will
rapidly
increase
with
the
increase
in
tube
temperature
and
protection
will
trip
more
quickly.
This
usage,
in
turn,
imposes
an
extreme
overload
on
the
tubes,
causing
them
to
flash.
The
tank
circuit,
therefore,
should
be
adjusted
until
tubes
deliver
maximum
output
for
a
given
rate
of
plate
current.
(4)
Overcurrent
protection
circuit
trips
too
quickly.
(a)
This
occurs
from
an
overdirve
in
which
whistling
instantaneously
swings
Ip
to
400
mA
or
greater.
Although
instantaneous,
this
large
current
will
rapidly
consume
the
life
of
power
tube
cathodes
and
microphone
in
the
SSB
exciter
microphone
gain
should
be
reduced
to
avoid
this.
mode
or
talks
ina
(b)
Variable
resistor
VR6
contained
in
the
control
unit
is
set
to
an
stronger
voice.
instantaneous
protection
level
of
below
400
mA.
Readjust
the
potentiometer
by
referring
to
ALIGNMENT.
9
(5)
Protection
circuit
trips
instantaneously
when
operator
whistles
into
the

TROUBLESHOOTING
TROUBLE CAUSE AND CORRECTIVE ACTION
(6) Linear amp output cannot (a) Meter switch is not set to SWR FWD position. If tank circuit is
be adjusted to a FWD scale adjusted with improper meter switch position, lp, plate dissipation
peak on the SWR meter. will increase in proportion to meter deflection and is quite dangerous
to tubes.
(b) BAND switch is not positioned in the desired frequency band. There
are two band switches — one on the exciter and the other on linear
amplifier. With an improperly set band switch, the plate VC cannot
be tuned and all plate input wil! be lost as plate dissipation.
Transmission should be interrupted more than 10 seconds after
protection circuit has tripped, to cool power tubes.
(c) Tank circuit is not switched to correct frequency. Check band switch,
and tank coils L7 and 8.
(d) Plate stopping capacitor C22 (0.002u/5kV) is not electrically
connected to plate choke coil L6 and tank circuit.
Bias control potentiometer is improperly set. Readjust referring to
ALIGNMENT.
Note: Bias can also become improper when line voltage is not AC 100 V. If
line voltage is low, Ip is high and, if is high, Ip is low.
(7) One or two tubes drain
much more or less
currents (1p) than the
other tubes in the absence
of signal.
Plate current varies
little with adjustment of
dynamic balance
trimmers.
The power tube is defective. This trouble often occurs with
flash-damaged tubes.
Replace with new tubes and readjust bias contro! potentiometer and
trimmer while referring to ADJUSTMENT.
10
a