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

e

ene

eneete

sen

enaees

:

4

BOTTOM

CHASSIS

VIEW

.....

0.

cece

eee

erent

teen

tees

5

CIRCUIT

DESCRIPTION

.....

0.0202

cece

eee

cert

eee

t

ents

6~8

TROUBLESHOOTING

.........0

cece

ec

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

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

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

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

Kenwood TL-911 User manual

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