Short version
This guide is designed to help you understand and how to test a voltage regulator. Please do not comment or ask questions in this thread so I can keep it only for updates and corrections. If you have a question, start a new thread in the appropriate subforum (Troubleshooting TV, computer LCD, etc).
Please read through the entire guide first. Corrections and revisions may be in subsequent posts below as I cannot edit post #1 once it is posted.
Long version
What is it
As the name implies, a voltage regulator is designed to regulate voltage to a desired constant output. For example, most modern electronics today have 5V DC standby that is on all the time as soon as it is plugged into the AC wall socket. Some components however require, say, 3.3V. A voltage regulator can be used to regulate the 5V down to 3.3V within a certain percentage (typically 1 to 2%).
Why is it important
Some components require a constant DC voltage in order to work properly. A voltage regulator like any other component can fail for a number reasons. When it fails, a number of symptoms can be seen including, but not limited to
a) poor, fuzzy, distorted, scrambled picture
b) power LED not turning on
c) blinking power LED
d) no picture
e) no sound
f) etc
How to identify a voltage regulator
Voltage regulators are normally found on the main or logic board. This board usually has the main CPU (or brains) of the electronic device. Voltage regulators can come in all types of different packages. See the photo below for examples (circled in red).
You can identify a voltage regulator by looking at its part number and finding its datasheet. Some common voltage regulator part numbers are 1117, 1084 and 7805.
How to test a voltage regulator
Testing a voltage regulator requires a digital multimeter. The test is simple and easy to perform. Note: Voltage regulators are typically "low" voltage. Most are 5V DC or less so there is little danger of you getting shocked, but as always, exercise caution when measuring power.
To test a voltage regulator (circled in red),
1) Set your multimeter (if manual range) to 20V DC or DCV for autoranging.
2) Put your black probe on a ground screw (circled in black). Leave it there the entire time. This is your ground.
3) Put your red probe on each of the pins including any "cut" or "stub" pin, but ignore the "fat" tab. The fat tab is "up" or "north". Number the pins left to right.
4) Report them like below along with the part number (include all lines on the IC) of the IC. Don't report "they all tested good". About once every 2 weeks, we get someone who reports that only to find out they did the arithmetic wrong or mis-interpreted the results. So report all the readings.
U100 -> pcb designation
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
How to interpret the results
First you have to identify whether you have a fixed or adjustable output regulator by checking its datasheet.
Let's take an example of 2 common regulators.
Example #1 - fixed regulator
Regulator #1 - Part number 1117-33
Typing in "1117-33 datasheet" into my search engine results in (also attached)
The datasheet tells you that the suffix, -33, denotes that 3.3V is the expected output voltage +/- 1%. So if your multimeter reading shows
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
then you have a good regulator since 3.301 is within 1% of 3.3V.
Here is an example of a bad fixed regulator
AS1117-18 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
In the above bad case, the part number AS1117-18 indicates that the expected output voltage is 1.8 (suffix is -18). However, we measured 3.301 which is well over the +/- 1% tolerance.
Example #2 - adjustable regulator
Regulator #2 - Part number 1117
From the same URL and datasheet, we can see 1117 is an adjustable regulator because there is no suffix. The correct output voltage should be the voltage reading on pin 1 (adj) + 1.25V.
Here is an example of good adjustable regulator.
AS1117 -> line 1 of the IC
pin 1 = 0.000
pin 2 = 1.250
pin 3 = 5.001
So in the above example, you can see that pin 1 = 0. So 0 + 1.25 = 1.25V should be the correct output voltage for pin 2.
Here is an example of bad adjustable regulator.
AS1117 -> line 1 of the IC
pin 1 = 1.250
pin 2 = 2.250
pin 3 = 5.001
In the above bad case, you can see that pin 1 is 1.25. So 1.25 (pin 1) + 1.25 = 2.50. So the correct output voltage for pin 2 should be 2.50, but we measured 2.25 or 10% off.
(2.50 - 2.25)/2.50 = 10% off
Misc Notes
1) A number of Vizio TVs seem to be plagued with bad voltage regulators. Certain models have bad U33, U9, U2, U6 etc. If you have a Vizio TV, I think it is mandatory that you check all your regulators regardless of the symptoms. It only takes about 5 minutes to do.
2) Thanks to PlainBill who taught me all about voltage regulators in this post.
3) If you have an analog multimeter, it will not be precise enough to give you accurate measurements. Time to get a digital one or borrow one.
This guide is designed to help you understand and how to test a voltage regulator. Please do not comment or ask questions in this thread so I can keep it only for updates and corrections. If you have a question, start a new thread in the appropriate subforum (Troubleshooting TV, computer LCD, etc).
Please read through the entire guide first. Corrections and revisions may be in subsequent posts below as I cannot edit post #1 once it is posted.
Long version
What is it
As the name implies, a voltage regulator is designed to regulate voltage to a desired constant output. For example, most modern electronics today have 5V DC standby that is on all the time as soon as it is plugged into the AC wall socket. Some components however require, say, 3.3V. A voltage regulator can be used to regulate the 5V down to 3.3V within a certain percentage (typically 1 to 2%).
Why is it important
Some components require a constant DC voltage in order to work properly. A voltage regulator like any other component can fail for a number reasons. When it fails, a number of symptoms can be seen including, but not limited to
a) poor, fuzzy, distorted, scrambled picture
b) power LED not turning on
c) blinking power LED
d) no picture
e) no sound
f) etc
How to identify a voltage regulator
Voltage regulators are normally found on the main or logic board. This board usually has the main CPU (or brains) of the electronic device. Voltage regulators can come in all types of different packages. See the photo below for examples (circled in red).
You can identify a voltage regulator by looking at its part number and finding its datasheet. Some common voltage regulator part numbers are 1117, 1084 and 7805.
How to test a voltage regulator
Testing a voltage regulator requires a digital multimeter. The test is simple and easy to perform. Note: Voltage regulators are typically "low" voltage. Most are 5V DC or less so there is little danger of you getting shocked, but as always, exercise caution when measuring power.
To test a voltage regulator (circled in red),
1) Set your multimeter (if manual range) to 20V DC or DCV for autoranging.
2) Put your black probe on a ground screw (circled in black). Leave it there the entire time. This is your ground.
3) Put your red probe on each of the pins including any "cut" or "stub" pin, but ignore the "fat" tab. The fat tab is "up" or "north". Number the pins left to right.
4) Report them like below along with the part number (include all lines on the IC) of the IC. Don't report "they all tested good". About once every 2 weeks, we get someone who reports that only to find out they did the arithmetic wrong or mis-interpreted the results. So report all the readings.
U100 -> pcb designation
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
How to interpret the results
First you have to identify whether you have a fixed or adjustable output regulator by checking its datasheet.
Let's take an example of 2 common regulators.
Example #1 - fixed regulator
Regulator #1 - Part number 1117-33
Typing in "1117-33 datasheet" into my search engine results in (also attached)
The datasheet tells you that the suffix, -33, denotes that 3.3V is the expected output voltage +/- 1%. So if your multimeter reading shows
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
then you have a good regulator since 3.301 is within 1% of 3.3V.
Here is an example of a bad fixed regulator
AS1117-18 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001
In the above bad case, the part number AS1117-18 indicates that the expected output voltage is 1.8 (suffix is -18). However, we measured 3.301 which is well over the +/- 1% tolerance.
Example #2 - adjustable regulator
Regulator #2 - Part number 1117
From the same URL and datasheet, we can see 1117 is an adjustable regulator because there is no suffix. The correct output voltage should be the voltage reading on pin 1 (adj) + 1.25V.
Here is an example of good adjustable regulator.
AS1117 -> line 1 of the IC
pin 1 = 0.000
pin 2 = 1.250
pin 3 = 5.001
So in the above example, you can see that pin 1 = 0. So 0 + 1.25 = 1.25V should be the correct output voltage for pin 2.
Here is an example of bad adjustable regulator.
AS1117 -> line 1 of the IC
pin 1 = 1.250
pin 2 = 2.250
pin 3 = 5.001
In the above bad case, you can see that pin 1 is 1.25. So 1.25 (pin 1) + 1.25 = 2.50. So the correct output voltage for pin 2 should be 2.50, but we measured 2.25 or 10% off.
(2.50 - 2.25)/2.50 = 10% off
Misc Notes
1) A number of Vizio TVs seem to be plagued with bad voltage regulators. Certain models have bad U33, U9, U2, U6 etc. If you have a Vizio TV, I think it is mandatory that you check all your regulators regardless of the symptoms. It only takes about 5 minutes to do.
2) Thanks to PlainBill who taught me all about voltage regulators in this post.
3) If you have an analog multimeter, it will not be precise enough to give you accurate measurements. Time to get a digital one or borrow one.
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