5.12

Question 1

When was new technology in circuit boards with LRU’s brought in?

Answer 1

1979

Question 2

What does LRU stand for?

Answer 2

Line Replaceable Unit

Question 3

What rate of unserviceablity did new generation computers have to old computers?

Answer 3

Three to four times higher under same handling conditions.

Question 4

What are Electrostatic sensitive devices (ESD) also known as?

Answer 4

Electrostatic Discharge sensitive devices (ESDS)

Question 5

How are ESD’s damaged?

Answer 5

By transient electrical static charges.

Question 6

What is the visible effect of transient electrical static charges?

Answer 6

There is no visible evidence on the circuit board

Question 7

What percentage of ESD problems do not cause total failure?

Answer 7

80-90%

Question 8

Why is ESD problems a problem?

Answer 8

Hard to inspect by maintenance shop personnel

Automatic test equipments are often not able to discover the problem.

Question 9

What factors contribute to static electricity build up?

Answer 9

Humidity
Temperature
Material
Form of Movement

Question 10

How is static caused?

Answer 10

Exchange of atomic electrons between two materials.

Question 11

How high is the effect of static electricity in non- conductors?

Answer 11

Very High

Question 12

If you only feel shock when getting an electric shock what was the voltage?

Answer 12

1500 - 2000V

Question 13

If you feel pain when getting an electric shock what is the voltage?

Answer 13

5000V

Question 14

At what voltage does it feel like a hammer has hit your finger when receiving an electric shock?

Answer 14

15,000V

Question 15

What voltage can cause damage to modern ESDS?

Answer 15

As low as 100V