Lesson 7 Chapter 4 - Troubleshooting Power Supplies

Question 1

Power supplies fail in 2 ways:

Answer 1

1. Suddenly
2. Over time

Question 2

What’s a tech’s first step when the computer will not start and the fan will not turn? (1) What are 2 things to check?

verify that…, check…

Answer 2

Verify that the system is getting power FIRST

Check if the outlet is bad and if the extension cord is plugged in

Question 3

The tech has confirmed that the system is getting power (outlet, cord) but it still won’t turn on, What’s the next step?

Use a… to check… coming out of…

Answer 3

Use a multimeter to check the voltages coming out of the power supply

Question 4

The voltages supplied by most PC power supplies can safely vary by as much as ___% of their stated values

Answer 4

+-10% (so for 12V, 10.8-13.2V)

Question 5

What setting do you use for the multimeter to test every connection on the power supply? (3)

Since all voltages are between ___V and ___V DC, set the multimeter to the ___V DC setting for everything

Answer 5

Use the 20 V DC setting

since all voltages are between -20V and +20V, set the multimeter to the 20V DC settings for everything

Question 6

Since PSU won’t turn on without being connected to a motherboard, what can you use in place of one to test the PSU?

Answer 6

ATX tester

Question 7

What’s an ATX tester?

Answer 7

It’s a small box with the typical power sockets and an on/off switch (look for one that supports 20-pin and 24-pin motherboard connectors)

It’s a motherboard temp replacement

Question 8

Can a multimeter help diagnose intermittent PSU issues?

Answer 8

Not really, The voltages will show up in tolerance. When it spikes or sags the multimeter can’t catch it.

Question 9

Whenever you experience ______ problems, your first guess should be that the ____ ____ is bad (3)

Answer 9

intermittent problems = power supply is bad

Question 10

Watch out for PSU that list their operating temperature at ____Celsius (about room temperature) as the inside of a PC is usually warmer which means less efficiency from the PSU

Answer 10

25

Question 11

What type of device connects to the motherboard via a 3 pin connector?

Answer 11

case fan

Question 12

A power supply that provides 750 watts at room temperature is likely to supply this in a warmer environment (2 words)

Answer 12

less wattage (less efficiency for PSUs in warmer environments)

Question 13

Electricity is measured by:
1. pressure =
2. speed of travel =
3. volts multiplied by amps =
4. resistance =

Answer 13

1. volts
2. amps
3. watts
4. ohms