Zenith J584W - Page 35

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33

Since

this

preamp

assembly

is

common

to

both

the

8WJR56/

8WJR57

and

the

15WJR29

chassis

which

have

different

B+

supply

voltages,

it

is

necessary

to

provide

different

drop



ping

resistor

(on

the

preamp

circuit

board)

in

the

B+.

The

magnetic

preamp

is

connected

to

the

36V

B+

on

8WJR56/

8WJR57

while

it

is

connected

to

the

53V

B+

on

Chassis

15WJR29.

Because

of

the

higher

gain

of

this

magnetic

preamp,

it

is

most

important

to

avoid

ground

loops

and

also

ensure

that

all

leads

from

the

phono

cartridge

and

the

magnetic

cartridge

preamp

assembly

are

properly

dressed.

Ground

loops

and

improper

lead

dress

can

result

in

hum

or

other

unwanted

interference.

FIGURE

23

~

MAGNETIC

PREAMP

SCHEMA

TIC