Massive Audio DB8000 User Manual download pdf (Page 66)

CONVERTER

CONVERTER

(A)

COMMON

Is)

COMMON

(C)

1-íg. 1. Broadcast receiver

oscillator circuit configurations

include

(a) tapped coil and

(b) standard coil

with

"gimmick"

winding.

In

converted oscillator (c), L3 is replaced by

Cl, and

padder C2

is

added.

5495

-C or similar)

as

close

as possible

to the

converter tube (12SA7) ,

and

keep

the antenna coil (a

J.

W. Miller B-

5495 -A

or

similar)

at a

reasonable distance

away

from the oscillator

to

prevent

interac-

tion.

After mounting

the coils, disconnect

the ends of the leads

going to the old

coils

and connect them

to the

appropri-

ate pins on the new coils. If

a lead is

too short

and

will not reach,

don't add

to

it; replace it

with a new piece

of

wire of the proper length. And

be

sure

to

keep

all leads as

short and

direct as

possible.

Upon examining

your

receiver, you'll

find

one

of the three

oscillator configura-

tions shown

in Fig. 1,

or some varia-

tion thereof. The tapped oscillator

coil

shown

in (a) may include

a

"gimmick"

winding (L3)

which

serves to bypass the r.f.

com-

ponent around the grid leak re-

sistor (R1)

.

If not,

a capacitor

(C1) will

serve

that function.

Fig.

2. In

a standard

BC receiver

the

loop

antenna (a) or equivalent

is

replaced

with a

J. W. Miller r.f. coil

as

shown in (b). A suitable

short-

wave antenna must be

hooked up

to

the coil

primary for

best results.

72

In Fig. 1 (b),

the

oscillator

has

two

separate

coils,

Ll

and

L2, in

addition to

gimmick LS. The third arrangement,

shown in

(c)

,

replaces

L3

with Cl. Since

the short -wave

coils are

not

equipped

with the

gimmick, your converted

re-

ceiver

must include Cl, whose value

should

be 100 pF.

Also

note

that

a

new

capacitor,

padder C2,

has been

added.

The

reason for

this

is explained in the

instruction sheet

that comes with the

coil.

The secondary of the antenna

coil is

wired

to replace the

loop antenna

as

shown

in Fig. 2 (b) , and the primary

goes between ground and

the outdoor

antenna.

The before- conversion

circuit

is shown

in

Fig.

2( a

)

.

(Continued

on page 98)

CONVERTER

TO

OUTDOOR

ANT.

OCOMMON

(A)

CONVERTER

(B)

POPULAR ELECTRONICS

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