Mitsubishi Electric MUX-25TV - E1 User Manual download pdf (Page 50)

Fig.

2. Etching-

and

-drilling

guide.

r1,3

Ti 1 B

- C6-

T2,1

D1-

D2-

-R2- -ÿFT1,1

FT1,

Components-placement

guide.

placement and

orientation.

If you go

the perf

-board route, you

can use

the

same

layout shown

in Fig. 3, but

you'll

have to refer back to

Fig. 1 for

wiring details and

leave

extra

room

for wiring.

Regardless of the

wiring

method you

use, pay careful

atten-

tion to the polarization

of the diodes,

lectrolytic

capacitors

and battery,

to lead designations

for

the

t ansformers,

flashtube, transistors

and SCR.

Also,

it's

a good

idea to use

sockets

for the transistors

and SCR

to simplify

servicing

the circuit

should

this ever become

necessary

and to

facilitate

the steps

in the

checkout

procedure.

When mounting

on the circuit

board, be

very

careful

to avoid over

tightening the

hardware,

or the

very

The only

component

the Safety

Beacon calls

for that

isn't readily avail-

able

from

the

usual

parts sources

transformer

TI in

Fig. 1.

Though you

must

wind this transformer

yourself,

the task

isn't particularly

difficult.

The

materials

you

need are

readily available

and consist

of a pot-

core

/bobbin as-

sembly

(see

Parts

List for type

and avail-

ability),

some

No. 30 and

No. 36

enam-

eled

wire and

thin tape.

Wind the

1/2/3 feedback

turns

(see

Fig.

first.

This winding

consists

turns of

enameled

wire

with

tap at the

fifth

turn. Wrap

exactly

10 turns

wire

onto

the pot core's

bobbin

and add

7 "to

this

amount.

Clip

the

wire and unwind

from the

bobbin.

Fold the

wire exactly

half.

Carefully

scrape away,

down

to bare

wire, '/4

the enamel

coating

from

both

ends

and

centered

the

fold.

Scrape

away

3/4

" of enamel

from both

ends

of another

3 "

length

wire

and

twist

one

end of

it together

with the

bared

wire at the

fold.

Solder

the center

tap connection

and

wrap

with insulat-

ing

tape.

Now, starting

31/2

from one

end,

wrap exactly

turns

this

wire

Winding

The Transformer

around the

bobbin. Use pieces

of tape

with the numerals

1, 2 and 3 on them

identify the beginning,

center tape and

end

wires, respectively.

When you're

finished

winding this coil,

you

should

have two

leads that measure 3

% "

and

one

that measures 3 "

in length.

Remember

the direction

in which you

wound this

coil

(draw

an arrow

pointing

in this

direction

the

bobbin).

Wrap

couple of

turns of thin,

preferably

Mylar, tape over the

feedback

coil.

Next comes the primary

winding,

which

must be "bifilar"

wound. That

is,

two

lengths of

wire

used

to make this

coil

must

wound

at the same

time

achieve

the tightest

possible coupling

between

the two coil

halves. (Tight

couplings

minimizes

voltage

spikes

that

appear

across QI

and

Q2.)

The 4/5/6 primary

winding

in Fig. 1

consists of

13 double turns

wire if

the

project

is to be powered

from a

4.2-

to-4.5 -volt

source or

27 double

turns if

it's

to be powered

from a

12 -volt

source.

Cut a

48 " length of

wire for the

13 -turn

96"

wire for the 27

-turn pri-

mary.

Fold the wire exactly

in half and

remove '/a

" of enamel

from the ends

and center

fold exactly

as described

above

for the feedback

winding.

Starting at the center

-tap lead and

holding the

wires together,

wind

the

correct

number of turns on the bobbin

in the same

direction as you

wound the

feedback coil.

Label the ends of

this

winding

with numbers

and 6 tags and

the center

tap

with

number 5 tag. Then

wrap a couple of

turns of thin tape over

the

winding.

The 7/8 secondary

winding in Fig. 1

made up

of 240 turns of No. 36 enam-

eled

wire

wound in

either

direction. Be

sure

to accurately count

the turns as you

wind

the

wire

onto

the bobbin, since

the

number of

turns

will

determine the

potential that

will

be applied

to the

flashtube.

When winding is

done,

se-

cure

the coil with a couple of

layers of

thin tape.

Then scrape away

1/4 " of

enamel

from both

wire

ends and

label

these

wires with the numbers

and 8.

Place the bobbin assembly

inside

the

pot core, arranging

the

winding leads so

that they don't obstruct assembly.

Then

secure the two

halves of the pot core

with a

couple

layers

tape. You can

now

install the

transformer on your

Safety

Beacon's circuit

board, referring

to Fig. 1

for wiring details.

/ MODERN

ELECTRONICS

/ April /986

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It In

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