Marantz 5220 User Manual download pdf (Page 45)

should

have 3/16" (5 -mm)

thick

polyurethane

foam

lining their

sides.

Punch

hole in the bottom of

each

can to allow wires

pass

through

for

connecting

the

speakers

into the cir-

cuit.

Fashion two circular

wedges of

polyurethane

foam to

fit into the bot-

toms

the cans,

where they

will

hold

the

speakers

the correct

distance

away

from and at

the

proper

angle

assure

firm

contact

with the

handset

when

the handset

is placed

in the

cans.

You

may have to

experiment

bit to

get

the

right wedge shapes.

Punch

hole through each

wedge.

Route the speaker

wires

through the

holes in the wedges

and

the

cans,

and

silicone

cement

the wedges

in place.

Then

connect

the

wires

from the

speaker

with

the

silicone

"gasket"

the output

and

the wires

from the

other

speaker

to the

input terminals of

the

modem.

If you prefer,

you

can

use an

induc-

tive

pickup

the receiving side

the

modem.

do so, you'll

have

to lower

the

value of R19,

(which

determines

the

gain

the

last

stage

the active

filter) to compensate

for the

lower

gain of

the pickup.

In this way, you

eliminate

the possibility

of external

noise pickup.

Test and Adjustment.

Set

TRANSMIT

Switch

S1 to LOW and

DUP-

LEX switch S2

to FULL.

Temporarily

connect

a jumper

wire from

pin 2 of

the 25 -pin connector

to a

voltage

source of

about

-12 volts dc.

This can

found at

the negative sie of

C2.

Connect a

frequency

counter

test

point

TP3 (at

/C7)

and

temporarily

connect

a jumper

across

D16.

This will

turn on

the transmitter.

Now, adjust

R77

for a

frequency

1270 Hz, ±5

Hz.

Remove

the

jumper

from pin 2

the

connector

and power supply,

and

ad-

just

R78

fora frequency of

1070 Hz, ±5

Hz.

Set the

TRANSMIT Switch

to HIGH and

replace the jumper

from pin 2

the

connector

to the

negative voltage

supply.

Adjust R75

for a

frequency of

2225

Hz, ±10 Hz. Remove

the

jumper

and adjust R76

for

frequency of

2025

Hz,

±10 Hz.

The

output of

the

modem

must now

be set

for -15 dBm

(0.14 V rms or

0.39

V p -p)

the telephone

line

when the

handset is in position

in the

modem's

acoustic coupler

by adjusting

R79.

Assuming you don't

have a standard

modem test

instrument

perform

this

adjustment, carefully

follow the pro-

cedure

below.

CIRCLE

5 ON

FREE INFORMATION

CARO

First, make

no measurements of

the

voltage on

your phone

line

until

you

have

dialed and

have a party on

the

other

end.

Next, be very careful

not

short

the telephone

terminals, and use

an ungrounded

meter to

make

all

measurements.

If your

meter doesn't

have

an OUTPUT

jack, place a

0.1

-µF

capacitor

series

with one of

its test

probes.

Set

the

TRANSMIT and DUPLEX

switches

to the Low and

FULL posi-

tions,

respectively.

Turn

the trans-

mitter by jumpering

D16.

Place

the

telephone

handset

into the acoustic

coupler.

(Make sure

the

handset

correctly

oriented.)

Then

connect

the

meter to

the telephone

connector

block.

(Do

not

attempt

use

a "key -

set"

telephone

that

has lighted

pushbuttons.)

Adjust

R79

for

-15

dBm,

0.14

V rms,

0.39

V p -p.

Connect

1000

-ohm

resistor be-

tween

the

audio

input terminal

the

active

filter

and

ground.

With a

100,000 -ohm

resistor connected

series

with

the

signal

"hot" output,

connect

a signal

generator

to the

audio

input

terminal and

the

generator's

ground

lead to the

mo-

dem's common

ground.

Monitoring

the output

with

fre-

quency counter, set

the

generator's

frequency

for

1170 Hz. Connect

the

MODEM I

AUDIO OUT

GND¢BREAK

TRACE

EIJ

GNDY

MODEM

DATA

DATA OUT

TTY

20mA

TRANSMITTING

SPEAKER

(MODEM

OUTPUT

e I

OUTPUT

FROM

LINE

(

V'MODEM

INPUT

IA)

SWITCH

"WHEN

RE-

TRANSMITTING

RECORDED

DATA

(B)

SELECTOR

MAGNET

DRIVER

(C)

TERMINAL

EIA(RS

-232)

CONNECTION

MODEM

Fig. .1. Ways to connect the modem

to tape

recorder,

an E!A terminal,

or a Mode! .ld TTY Teleprinter.

counter

between

TP3

and

ground

and

a dc

voltmeter

between TP1

(floating

reference)

and

ground.

Adjust R10

through

its

entire

range, observing

where

the

monitored

voltage swings

smoothly

between

positive

and

nega-

tive.

This

the

lock

range of

the

PLL.

Adjust R10

that

the

meter

indicates

zero

within

the

lock

range.

Perform

this adjustment

several

times

to be

sure

you

haven't adjusted

outside

the

lock

range;

false

indications are

pos-

sible

there.

Direct

-Line

Hookup.

To wire

the

modem directly

to the

telephone

line,

the telephone

company

requires

that

you

use a

DAA

(Direct

Access

Ar-

rangement)

to isolate

the

two.

The

lowest

-cost system

available,

gener-

ally

renting

for

$2 to

month,

is the

CDT

(1001A) coupler.

It has a switch

that cuts

the

telephone out

and

the

coupler

in when

turned on.

The

wiring

diagram

for

this

setup

is shown

in Fig.

2A.

When the CDT

used,

1C8

is wired

"active

hybrid" circuit

that can

subtract

the output

the

transmitter

from

the

input of

the

receiver,

shown

Fig. 2B.

Terminal

E3 is con-

nected to

the output of

the

modem,

which

is also connected

to one

side

the phone

line.

goes to

the

input

terminal

the

modem and

the other

side

the phone

line. Ideally, R62

should

the same

resistance

the

line

impedance, specified

the

tele-

phone company

600 ohms,

when a

DAA

used.

However,

this

resistor's

value can

trimmed

if "balancing

out"

adjustments

are

needed.

Tape

Recorder

Connections.

The

phone jacks, .11, J2,

and J3, permit

the

use

the

modem

with a tape

recorder

record data

from the

terminal

from the phone

line, and

to play

the

data back

to the terminal

for the phone

line, or

both.

The

jacks

are

wired

into the

modem

as shown

in Fig. 3A.

Jack

then

con-

nects to

the

transmitting

speaker

and

serves

the

interconnect

for the

mic-

rophone

input

to the

tape

recorder.

Jacks J2

and

connect

between

and

E2 and

ground.

(Make

sure you

break

the

foil

between

El and

E2 on

the circuit

board

if you use

this

mode.)

JackJ2

goes

to E1,

which

is the output

the

first

stage

the

filter, and also

feeds

the

microphone

input of

the

tape

recorder

when

is used.

Jack

breaks

the connection

between

and

E2 and

allows

the tape

recorder

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Marantz 5220 User Manual Page 45

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