Mcmartin Tbm-2500 User manual

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INSTRUCTION

M

NUAL

TBM

-2soo

RF

AMPLIFIER

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INSTRUCTION

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.1ANU.A.L

I . TBM-2500

RF

AMPLIFIER

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I.

II.

III.

IV.

V.

VI.

VII.

TABLE

OF

CONTENTS

G

eneral

Deacription

Technical

Specifications

In

stallation

and

Initial

Adjustment

In

spection

L

ocation

Connections,

Input

Connections,

Output

Initial

Adjustment

Operation

Interference

Filter

Carrier

Feilure

Relay

Circuit

Description

Parts

List

Schematic

I.

GENERt\L

DESCRIPTION

l

2

3-4

3

3-4

4

t9

...

The

Tm!-2500

is

designed

to

a

□

plify

a

transnitted

FM

si~nal

toe.

l

evel

suitable

for

any

Frequency,

Modulation,

or

Uultiplex

station

monitor

when

remote

operation

is

desired.

Although

specifically

designed

for

the

Nd1artin

TBM

-

3000,

TBM

-

3500,

end

TBM-4000

,

it

is

also

designed

for

u

se

with

other

brands

of

!llonitors

which

require

a

higher

input

si,gnal

leve

l.

The

TBH

-2500

has

two

separate

RF

outputs.

One

is

high

level

and

the

ot

her

is

l

ow

level.

Sufficient

isolation

is

provided

between

the

output

to

inter

action

bet;;een

McMartin

o.nd

other

type

monitors

.

A

carri

er

fai

l

ure

relay

is

inco

rp

orated

for

connection

to

a

wa

rnin

g

system.

Should

an

RF

failure

occur

at

the

transmitter

,

the

relay

is

activated

. A

front

panel

meter

indicates

relative

input

signa

l

st

rength

.

A

cut-to~

frequency

antenna

,

50

feet

of

coaxial

cable

with

c

onnectors

is

also

supplied

. Long

tube

life

end

st~ble

operation

were

the

prime

design

consideration

of

the

TBM

-2500.

-

1-

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TECHNICAL

SPECIFICATIONS

Operating

Frequency

RF

Sensitivity

Rear

Chassis

Connections

RF

Input

High

RF

Output

Low

RF

Output

Carrier

Relay

Rear

Chassis

Control

Top

Chassis

Contr

ol

Fron·c

Panel

Controls

Front

Panel

Indicstors

Tubes

Dimension3

Finish

S

hipping

Weight

Power

Antenna

Coaxial

Cable

- 2-

88-10') JllC

1

00

µv

input

for½

watt

output

1000 µv

input

for

2

watts

output

·

50

ohl!ls

coaxial

50

ohms

coaxial

50

ohms

coa

xial

3

termin~l

board

(SPDT)

Carrier

Reley Threshold

RF

Gain

Complete

RF

tuning

Power

OU-OFF

RF

Level

Meter

Pilot

Lemp

l -

6AK5

2-6AG5

l-6BH6

1-

5763

Standard

Re.ck

Panel

19" x

5¼"

Depth behind

panel

7"

Natural

Gray

Panel,

Cadmium

Chassis

19

lbs

.

1

20

VAC,

50

-

60

cps,

55

watts

Cut-

to-frequency

, 4

element

yegi

w

ith

coaxial

fitting

.

RG-59U

(50')

'

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INSTALLATION

and INITIAL

ADJUSTMENT

Inspection

:

Upon

receipt

of

your

TBM

-2500, remove

it

from

the

packing

material

and

inspect

for

any damage

caused

in

transit

due

to

handling

or

vibration

.

If

damage

is

found,

notify

the

shipping

agency

and

advise

McMartin

Industries,

Inc.

of

such

action

.

Location:

Installation

preferably

should

be

made

in

a

standard

equipment

rack

which

also

contains

the

station

monitor(s)

with

which

it

will

operate

. The equipment

rack

should

be

located

as

near

to

the

antenna

as

is

practical

. Adequate

ventilation

is

necessary

for

long

term

depend-

ability

of

the

TBN-2500.

Free

convection

air

flow

from

bottom

to

top

should

be

allowed

as

the

chassi

s

is

designed

wit

h

ventilation

screens

located

by

the

final

output

tube.

Connections,

Input:

The

AC

line

cord

is

plugged

into

a nominal

120

VAC

, 50-

60

cps

receptacle

. ,

With

the

50

feet

of

coaxial

cabl

e

supplied

,

connect

the

antenna

lead-in

between

the

antenna

and

ANT

D!PUT

to

the

TBM-2500

.

Follow

normal,

good

practice

when mounting

the

ar.tenna

and

running

the

leed-in

.

At

the

TBM

-2500,

dress

the

l

r;

ad-

in

away

fro~

the

output

cables

.

C

onnections,

Output

:

Either

the

HI

our

or

LO

OUT

output

is

satisfactory

for

operation

with

any McMartin monitor(TEM-3000,

TBM

-3500,

TBM

-4000).

If

a

combination

of

two McMartin

monitors

ere

being

operated

,

use

both

outputs

and

feed

th

e

monitors

separately

.

If

a McMartin

monit

or

is

being

operated

with

another

type

of

monitor

,

connect

the

McMartin

to

10

OUT

and

the

other

monitor

to

HI

OUT

.

If

only

one

nonitor

of

any

type

is

being

operat

e

d,

connect

to

the

HI

OUT

.

Coaxial

cable

is

used

(keep

as

short

as

possible)

for

connection

bet·,,een

the

TBM

-2500

output

and

the

oonitor

input(s)

. Amphenol Type

83

-I

SP

(

or

equivalent)

connectors

are

required

.

If

ocly

one

monitor

is

being

used,

be

sure

to

cap

the

unused output_

receptacle

.

This

will

prevent

unwanted

RF

radiation

.

Init

ial

Adjustments:

Turn on

the

AC

power

for

the

TBM

-2500 and

any

monitor

which

is

being

oper9.ted. Allow

sufficient

time

for

warn;.

-up

of

all

equipment.

Orient

the

antenna

for

maximum

indication

on

the

SIG

NAL

LEVEL

meter.

If

the

SIGNAL

LEVEL

meter

goes

off

-

scale

during

ante!jna

orientation

,

reduce

the

RF

GAIN

control

(top

chassis)

.

T_he

TBM-2500

i s

factory

aligned

to

your

f r

equency,

however due

to

unpredictable

input

and

output

loading

effects

et

your

location

,

the

complete

alignment

should

now

be

re

-

touched

.

In

the

following

order,

adjust

for

maximum

indication

on

the

SIGNAL

LEVEL

meter

:

ANT

, 1,

2,

3, and

FINAL.

Repeat

this

procedure

until

no

further

improvement

can

be

made

.

Reduce

the

RF

GADi

control

as

may

be

neceszary

.

-3-

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III.

INSTALLATION

and INITIAL

ADJUSTMENT

(cont

. )

At

this

point,

check

the

RF

input

level

indicated

on

the

monitor(s)

bei

ng

operated

.

Adjust

the

monitor

RF

input

control

for

the

proper

level

into

the

monitor

.

Fallo~

the

manufacturer's

reco~endation

.

Initial

adjust

~

cnt

is

now

cor.iplete.

IV.

OPERATION

Optimum

cperation

of

tbe

TB[-1

-

2500

is

with

the

RF

GAD1

control

set

as

lcw

as

uossible

while

still

maintainin

g

the

reco

!DJ'a

ended

RF

input

level

tothe

moni

tor(s)

. Check

the

settin

g

of

the

monitor

RF

input

leve~

control.

It

may

be

desirable

t~

increase

the

rnonitor

RF

level

control(

s)

and d.:::crea.se

the

TEM-2500

RF

GAIN

control.

If

this

is

done,

repeat

the

co1r.plete :_

:1

-25co

alignnent

once

again

,

st

a

rting

with

L-2,

L-3,

etc.

With no RF

carrier

present

at

the

input

to

the

TBM-2500,

con-

siderable

noise

may

be

generated

at

the

output.

Tnis

would ca.use

erratic

readings

on

the

connected

noni

tor(

s)

.

In

this

eve:it

tl;le

T3).1

-

2500

should

be

turned

off.

V.

INTERFERENCE

FIL~R

:

··

- - · Most

station

xr.oni

t o

rs

are

generally

broad-

tuned

and

therefore

not

capable

of

s~pe.rating

strong,

alternate

channel

signals.

Toe

ToI-1

-

2500

c

ontains

a pa:-a

llel

re

so

r.ant

tuned

circuit

which

when

tuned

properly,

·,1ill

reduce

the

intensity

of

the

int

e

rferring

signel.

As

the

T3;,!-2500

is

shipped

this

filter

is

tuned

to

a f~equency

ether

than

the

station

frequency

.

If

interference

is

not

a

proble:t

it

is

u:iecessary

to

e.djust

t h

is

filter.

If

an

interferring

station

is

present,

adjust

the

FILTER

(

top

chas3is)

for

maximum

rejection

.

After

this

adjustment

is

~ade,

it

will

be

neces

-

sary

to

re-align

the

antenna

coil

L-1,

e?ld

RF

coil

L-2.

VI

•

CARRIER

FAILURE

RELAY:

The

carrier

failu

re

relay

is

factory

adjusted

fo

r a

threshold

c~rresponding

to

approx

i

mately

50

µy

RF

input

l

evel

at

the

antenna

input.

Should

the

RF

carrier

level

fall

below

this

point

,

the

relay

is

activated

.

The

required

signal

to

reopen

relay

is

approxima.tely

250

µv,

The

thres

-

hold.can

be

adjusted

to

any

point

by

the

rear-chassis

RZLAY

control

.

The

RELAY

ter~inal

board

has

3

connections

to

an

SFDT

relay.

Ter.ninal

Bis

the

common

pole

.

Terminal

A

is

shorted

to

B

during

normal

operation

. With a

carrier

failure,

Bis

shorted

to

C. The

relay

contacts

are

rated

a 1 a~p. Almost any

type

of

external

·

elar~

circuit

nay be

connected

to

this

auto

m

atic

relay

circuit

.

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✓

.cMartin

B1·oadce.st

and

Audio

Products

~re

warranted

to

be

free

from

d~fects

in

·,:or!•;:nianship -

Fo::mv.e~

.

At

our

discretion

we

wil

l

exchance

or

repair

ony

defective

unit

or

ccrnponc!lt,

at

any

tille,

\Jhhout

charce

.

Material

and componerrts

are

iuaranteed

for

e

minir.1uri1

period

of

90

days

frou

the

dste

of

the

original

purchase.

Trans

-

portation

charges

r:

1ust

be

prepaid

on

equip

r.

ient

returr~ed

for

warranty

service.

This

;,arranty

does

not

extend

to

any

cf

our

products

which

have

been

subjected

to

;dsuse

,

ne5lect

,

accidents

,

inco:..·rect

wiring

not

our

o~m,

improper

in-

stallation,

or

to

use

in

violation

of

the

instructions

furr.ished

by

us;

nor

to

units

that

have

been

altered

outside

our

factory

.

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VII.

CIRCUIT

DESCRIPTION

:

A

signal

will

be

traced

through

the

TBM-2500

referring

to

the

schematic

.

RF

input

from

the

antenna

is

fed

through

ANT

INPUT

to

the

tuned

circ

uit

L-1 and

the

grid

of

V-1. A

parallel

resonant

circuit

FL-1, when

tuned

to

an

interferri

ng

frequency,

presents

a

very

high

impedance

block

t o

the

grid

of

V-1.

The

RF

signal

is

amplif

i

ed

consecutively

by V-1, V-2, and

V-3

.

L-2,

L-3, and L-4

are

the

t

u:1ed

circuits

forming

an

inpedance

coupled

eu~lifier.

The

gain

of

this

amplifier

is

controlled

by

adjusting

the

cathode

bias

of

V-2. Each

stage

of

a~plification

is

shielded

from

the

others

by

individual

conpartments

within

the

chassis

.

Filament

end

plate

voltages

are

fed

to

these

co~partme:its

via

feed

-

through

capacitors,

thus

preventin

g

interaction

between

the

stages

. ,

The

plate

output

of

V-3

drives

the

final

amplifier

stage

, V-4.

This

final

RF

output

stage

is

a

shunt-fed

class

C

amplifier

.

For

optimum

stability,

V-4

is

neutralized

with

a

srcall

voltage

fed

back from L-5

to

the

input

of

V-4 .

Capacitor

C-

111

and

R?

choke

CH

-2

for

m

the

neutra-

liz

ation

network.

L-5

is

th

e

output

tank

coil

and

is

tapped

to

provide

a

no~inal

output

impedance

of

50 oh~s . R-18 end C-21

form

a

voltage

divider

and

also

attenuate

200

kc

.

This

filter

action

serves

to

reduce

interference

fr

om

monitors

which

radiate

200 kc from

their

internal

frequency

counter

circuits

. The

voltage

divider

enables

connection

of

two

monitors

which

require

differen~

input

levels

.

A

s8.!D.ple

of

the

RF

appearing

across

L-5

is

i·ectified

by

D-1.

This

negative

DC

voltage

appears

across

R-

22,

and

meter

M-1

(in

series

with

R-

21).

The .::ieter

indic

ates

relative

RF

input

signal

strength

.

Adjustm

ent

of

R-22

determines

the

threshold

of

the

relay

control

tube

V-5. .

The

primary

of

the

power

trensformer

(T

-

1)

is

fused

and

RF

filtered

.

Silicon

rectifiers

,

SR

-1 and SR-2 form a

'DC

voltage

doubler.

The

filament

winding

of

T-1

supplies

only

6.0

volts

for

extended

tube

lif

e .

-

5-

•

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C-1

C

-2

C-

3

C-4

C-5

c-6

C-7

C-

8

C-9

C-10

C-ll

C-12

C-13

C-

14

C-15

C-

16

C-17

C-18

C-19

C-

20

C-

21

C-

22

,

C-23

P

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C-24

C-25

C-

26

C-

27C

C-27D

C-28

C-29

C-30

C-

31

C-32

C-

33

C-34

C-

35

c-36

C-

37

C-

38

R-1

R-2

R-3

R-4

R-5

R-6

PARTS

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220

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SPST

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IVICMARTIN

i,1rM,utm

industr

Ies

Inc

■

4500 S•.)uth

76th

Street

■

Omaha.

Nebraska

68127

■

(

402)

331

-2000

•

Telex

484485

McMartin TBM-2500 User manual

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