Determining Types of Failures

TM 11-6625-539-15-2

3-6 Determining Types of Failures

3-5. Methods for Servicing S e m i c o n d u c t o r

The test set can be used to determine the type of

Circuitry

failure encountered, and some of the tests can be used

to verify the findings of other tests. The chart in para-

Test Set, Transistor TS-1836B/U is designed so that

graph 2-7 lists the types of failures that can be found

it is a safe instrument to use with semiconductor cir-

and the manner in which the test set can be used to

cuitry. The voltage and current levels that the instru-

determine the type of failure. An open and a shorted

ment can supply to the device are controlled so that

diode both give zero meter deflection on the in-circuit

diode measurement test. If the diode is shorted,

the accidental misplacing of leads will not damage

switching the meter to the C-E OHMS test will give

any semiconductor device; therefore, any device fail-

a 0-ohm reading. If the C-E ohms tests shows a resist-

ure would be caused by equipment operation and not

ance or an infinity reading on the meter, the diode

is open.

the manner which the test set is used.

a. Transistors.

Ohms (E-B, C-B, C-E)

Beta

Type of failure

Emitter-to-base

ohms

test.

Meter

indicates

infinity

Open emitter-to-base junction _ _ _ _

Beta reads infinity _ _ _

emitter-to-base

load.

Emitter-to-base

ohms

test.

Meter

indicates

ohm.

Shorted

emitter-to-base

junction

___

Test

set

cannot

set

for

BETA

CAL.

Test set cannot be set for BETA

Emitter-to-base

ohms

test.

Meter

indicates

low

re-

High leakage between the emitter-

sistance.

to-base

junction.

CAL.

Collector-to-base

ohms

test.

Meter

indicates

infinity

Open

collector-to-base

junction

____

Test

set

cannot

set

for

BETA

or collector-to-base load.

CAL.

Collector-to-base

ohms

test.

Meter

indicates

ohm.

Shorted collector-to-base junction ___ Test set cannot be set for BETA

CAL.

Collector-to-base

ohms

test.

Meter

indicates

low

re-

High

leakage

between

the

collector-

Test

set

cannot

set

for

BETA

sistance.

CAL.

to-base

junction.

Collector-to-emitter

ohms

test.

Meter

indicates

in-

Open collector-to-emitter _ _ _ _ _ _ _ _ _ Test set cannot be set for BETA

finity

the

collector-to-emitter

load.

CAL.

Collector-to-emitter

ohms

test.

Meter

indicates

ohm.

Shorted

collector-to-emitter________Test

set

cannot

set

for

BETA

CAL.

Test set gives reverse indication

Collector-to-emitter

ohms

test.

Meter

indicates

low

High

leakage

between

the

collector-

for

BETA

CAL.

resistance.

to-emitter.

b. Diodes.

Meter indication

Ohm (C-E)

Type of failure

In-circuit diode measurement

Shorted diode_ _ _

0 meter deflection _ _ _ 0.

Open diode _ _ _ _

0 meter deflection _ _ _ Infinite or circuit

resistance.

3-4