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Common fault Of IC Voltage Regulators

By Jestine Yong on October 25, 2012

Those days you could only see the common 3 legs 78 and 79 series of voltage regulator ICs in circuit boards but now it is common to see IC voltage regulators that have more than 5 pins. Some have single output and some have multiple output voltages. The common fault for a voltage regulator IC are:

Shorted IC
No output voltage
low output voltage
a too high output voltage and
IC breakdown when under load

Finding the IC problems on 1 to 4 is not difficult but locating the IC that breakdown under load will be a bit difficult but unless you know what to do. Lets take a power LED blinking problem in an equipment as example. For your information most power LED signal source is coming from a microcontroller (MCU) chip. If you get a good supply voltage to the IC voltage regulator and fluctuate output you will know that either the IC or the mainboard circuitry have problem. The problem now is that when you lifted up the output pin of the ic voltage regulators you will see that the output voltage is back to normal and ths will promt you thinking that the mainboard or the circuitry have problem. The actual fact is that the ic voltage regulator itself can't sustain the current draw from the mainboard.

You can confirm if the ic voltage regulators is good or bad by substituing a working one or use an automobile bulb to test it. A good IC should produce a steady light and bad one will not have any light or blinking light.

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8 Comments

dicksy

October 27, 2012 at 8:55 pm

these articals help us verymuch.thanx a lot

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- Jestine Yong
  
  October 27, 2012 at 8:59 pm
  
  Hi Dicksy,
  
  You are welcome!
  
  Jestine
  
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Kelum

November 8, 2012 at 8:47 am

thanks

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yosry mostafa

November 8, 2012 at 6:05 pm

It is really a good article
But I want to know some of the things in this article. Even sure whether I understand the article good or not

1) is the power led like the automobile bulb?
where it has 2 pins and work with dc voltage
2) does the signal come from the mcu to relay or transistor base to control in the power led lighting or it work directly from mcu?

does you mean with fluctuate output that i have many output to connect them with voltage regulator to be sure is it stable or not stable under various loads ?

does the mainboard circuitry is the load of voltage regulator ?
and what is the difference between mainboard and circuitry in( this will prompt you thinking that the mainboard or the circuitry have problem)

does the ( blinking light ) mean it light but weak light ?

Excuse me if I was weak in English and I'm not that good at expression
I hope that not to be disturbed
Your student
Yousry Moustafa

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- Jestine Yong
  
  November 8, 2012 at 9:21 pm
  
  Hi Yosry,
  
  1) is the power led like the automobile bulb?
  where it has 2 pins and work with dc voltage
  
  ===Automobile drain more current than LEDs. Yes both works with DC.
  
  2) does the signal come from the mcu to relay or transistor base to control in the power led lighting or it work directly from mcu?
  
  ====MCU sends out a ON signal to trigger a transistor so that it can activate a relay
  
  does you mean with fluctuate output that i have many output to connect them with voltage regulator to be sure is it stable or not stable under various loads ?
  
  ====Voltage regulator ICs can be connected to many loads but it should be stable and wull not fluctuate unless the load or the ICs itself have problem
  
  does the mainboard circuitry is the load of voltage regulator ?
  
  ===Yes
  
  and what is the difference between mainboard and circuitry in( this will prompt you thinking that the mainboard or the circuitry have problem)
  
  ====Mainboard consist of many section of circuitry and each section can be powered up by one or few supply voltages from SMPS or voltage regulators ICs.
  
  does the ( blinking light ) mean it light but weak light ?
  
  ====A Good voltage regulator ICs should produce a stable light when a bulb is connected.
  
  Jestine
  
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yosry mostafa

November 9, 2012 at 6:40 am

thank you
you are a great teacher

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- Jestine Yong
  
  November 9, 2012 at 6:42 am
  
  HI Yosry,
  
  You are welcome!
  
  Jestine
  
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opokusolomon

October 29, 2017 at 6:37 pm

This one is not coming at all

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