Heathkit IM-4100 - Page 57

82 pages

Save Page as PDF

To Next Page

To Next Page

To Previous Page

To Previous Page

Loading...

Ge-jHeatTHKIT?

The

trailing

edge

of

the

pulse

from

pin

11

of

IC18D

triggers

1C16

and

produces

a

200

millisecond

output

pulse.

This

pulse

first

turns

on

IC17D

and

clears

1C13B.

The

pulse

from

pin

6

of

IC16

also

gates

IC18A

and

IC18B,

and

resets

the

decade

counters

(IC3

through

IC7)

to

zero.

1C17C

then

‘changes

state

and

clears

1C13A.

Any

overrange

information

has

already

been

entered

into

data

latch

I1C14.

Period

Mode

The

input

signal

at

IC15E

pin

9

is

coupled

through

1C15

gates

E

and

F

to

IC13B,

the

GATE

control

flip-flop.

The

selected

time

base

signal

is

applied

to

IC2

pin

11

and

counted

by

the

decade

counters

during

the

time

IC2

is

GATED

on

(which

is

the

time

of

one

period

of

the

input

signal).

Totalize

Mode

1C2D

pin

1

and

IC15E

pin

10

are

held

low

by

Mode

switch

SW3.

This

inhibits

the

GATE

function

of

the

Counter

and

the

input

signal

at

IC2A

pin

3

is

coupled

through

gates

A

and

E

to

the

counters.

Switch

SW5

resets

the

Counter

in

all

modes

by

grounding

IC18B

pin

5.

If

you

reset

the

Counter

with

an

external

GATE

pulse,

the

pulse

is

coupled

through

R33

and

SW6

to

1C17A

pin

1.

This

creates

a

low

at

pin

6

of

1C17B

which

turns

off

GATE

IC2A

so

no

signal

can

propagate

through

IC2

to

the

counters.

Page

51

OVERRANGE

DETECTION

lf

the

count

passes

from

99.999

to

100.000,

a

pulse

is

produced

at

the

D

output

(pin

11)

of

IC7.

This

spillover

toggles

1C13A,

which

is

a

standard

JK

flip-flop.

The

J

input

of

this

IC

is

tied

to

logic

1

(+5

volts).

This

causes

the

Q

output

to

latch

to

a

logic

1

condition

whenever

the

CK

input

is

toggled.

The

Q

output

remains

in

this

condition

until

a

logic

O

is

applied

to

the

C

(clear)

input.

1C14

is

quadruple

2-input

NAND

gate

package

used

as

a

data

latch.

The

logic

level

at

pin

1

of

1C14

will

be

transferred

to

pin

6

when

pin

2

and

pin

13

are

both

at

a

logic

1.

A

logic

O

at

these

inputs

will

inhibit

the

transfer.

The

output

of

this

latch

is

used

to

short

out

the

overrange

LED

when

no

spillover

has

occurred.

The

overrange

indicator

lights

whenever

IC13

pin

15

is

at

a

logic

1.

POWER

SUPPLY

Transformer

T1

steps

down

the

line

voltage

to

the

proper

value

of

AC.

Diodes

D7

through

D10

rectify

the

AC

and

capacitors

C16

and

C17

filter

out

the

pulsations.

1C27

regulates

the

DC

to

a

constant

five

volts.

CIRCUIT

BOARD

X-RAY

VIEWS

NOTE:

To

find

the

PART

NUMBER

of

a

component

for

the

purpose

of

ordering

a

replacement

part:

A.

Find

the

circuit

component

number

(R5,

C3,

etc.)

onthe

X-Ray

View.

B.

Locate

this

same

number

in

the

“Circuit

Component

Number’

column

of

the

“Parts

List’’

in

the

front

of

this

Manual.

C.

Adjacent

to

the

circuit

component

number,

you

will

find

the

PART

NUMBER

and

DESCRIPTION

which

must

be

supplied

when

you

order

a

replacement

part.