Epson L90P - TM Two-color Thermal Line Printer Bedienungsanleitung PDF herunterladen (Seite 63)

T HE INCREASING

use of digital IC's

many

experimenters'

projects has

created

a need for

a low -cost

in- or out

of- circuit

tester for

these

complex

semi-

conductor

devices.

Up to now, most

ex-

perimenters

have

done

their best using a

conventional

voltmeter

trace the on-

off signal

a circuit

board. This is

difficult

process

at best. Making

contact

with

a narrow foil

strip

and

looking

at a

meter

at the same

time is trouble

enough,

but

most

of the

time

the pulses

are

so short

that they don't

even

on the meter.

It is

even

difficult to

test IC's

that

are

not

connected into

known

operating

circuits.

The

"IC Telltale"

described here

was

designed

solve many

of these

testing

problems. It

will test, in

or out

of the

circuit, the

RTL

(resistor-

transistor -log-

ic)

IC's such

as the MDtoropa

MC700P

Telltale

Zwv-waff

system

to check

digital

circuits

TROEMEL

series

and the

Fairchild 1í.L900

series

that are

used

number

POPULAR

ELECTRONICS

projects.

The

IC Telltale

consists

of two as-

semblies: a

10,000

-ohm

input- impedance

probe for checking

IC's

mounted on a

circuit board; and a test set with a built

and

-Hz trigger

pulse

generator

with

14 -pin in -line

and 8 -pin round IC

sockets for out -of- circuit

tests.

The oscil-

lator circuit in the

test

set can

also be

used as a trigger source for finished IC

boards, if desired.

The readout is

built in the probe

and

consists of a small pilot lamp

that is on

when

the logic is

at, or

near, ground

level

and goes "off" when

the

logic is

at,

near, +3.6

volts. The probe

can be

used to trace

digital

signal through

foil

patterns

and

integrated

circuit con-

nections.

April, 1969 69

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