How to test a voltage regulator

[retiredcaps]

Regulars will hopefully appreciate this new guide I just wrote so you don't have to explain it over and over again.

https://www.badcaps.net/forum/showthread.php?p=261329

PS. Same thread also posted on Troubleshooting Computer Displays as some regulars read one, but not the other.

[tom66]

Re: How to test a voltage regulator

Fantastic guide - will be very useful for newbies.

Only one comment I'd make. The IC at the top is an LM2576T - a switching regulator, not LDO. Testing its output should be done at one end of the inductor - the "680 JYE" component.

[selldoor]

Re: How to test a voltage regulator

Fantastic guide - will be very useful for newbies.
.

And Me! - Thanks retiredcaps - got it bookmarked next to "2StoB"

[mariushm]

Re: How to test a voltage regulator

Uhm... you have there an example of a bad voltage regulator which should output 1.8v but it outputs 3.3v.

Yes, theoretically it's bad but generally even the fixed output regulators can be adjusted to other voltages by adding feedback resistors to the ground pin.

It should almost never happen in real world as these 1117 regulators cost pennies at volume purchases but especially when their output is a popular voltage like 2.5v or 3.3v, one should consider the manufacturer may have used the same part with adjusting resistors on it.

Maybe change the example to say instead of 3.3v something else, let's say 1.2v

...I'll second tom66 to say some regulators are switching regulators, which need an inductor and a diode to work: people should check the diode and the inductor.

Also, some switching regulators need to have the capacitor on the output with a somewhat higher ESR... somewhere around 0.4-1 ohm.

Some people get trained to think anything over 0.3 or so is bad capacitors but that's not always the case and it can affect the regulator's stability if such low ESR capacitors are used. Don't rush into replacing capacitors unless you tested everything and you think they might cause problems.

[woaimi]

Re: How to test a voltage regulator

thank you, that helps newbie like me to gain some real life experiences.

[budm]

Re: How to test a voltage regulator

Retiredcaps, glad you make the write up for the LDO. You may want to add about the two resistors used for setting up the output voltage of the adjustable LDO (that is one way to tell if it is fixed or adjustable LDO), there is formula for it.