LM7805 or 7815

[jimilee]

I've compared data sheets, tell me if I'm missing something, but they are interchangeable, yes?

[Aristatertotle]

Lm7805 is a 5 volt regulator while the lm7815 is the 15 volt version.

[jimilee]

Would that explain why I've blown 2 electros?


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[somnif]

Most electros I know are rated for at least 16v, so maybe not (though there are current issues in play as well), but still running 15V in a circuit designed for 5 is likely going to cause problem.

[daleykd]

Like it was mentioned, the 7805 is 5V, the 7815 is 15V (7812, 12V; 7818, 18V, etc.)

[To make things more complicated, the 7905 is -5V, the 7915 is -15V, etc.]

What is NORMALLY interchangeable in our DIY pedals is the LM7805 and the 78L05.  The difference here is the TO-220 vs TO-92 and the amps (the LM7805 can handle more).

As for the elctros... that's weird.  Try the 7805 and see what happens.

[jimilee]

I should elaborate a little, I'm working with the rust bucket.


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[daleykd]

I should elaborate a little, I'm working with the rust bucket.


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Oooo, so he wants a LM7815 (the TO-220), and he's asking for 18V to start.

He also states that you should have at least 25V caps.  That makes sense since you're starting at 18V.

What voltage are you using for your caps?  Anything less than 25V will go kaput.

[jimilee]

Good point, I'll have to check what I got.


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[EBRAddict]

The build doc specifies all = 25V min. Note that one electro cap is unipolar / non-polarized. Which cap is blowing?

I'd be stunned if a 16V cap was suffering catastrophic failure under 15V or even 18V conditions.

[jimilee]

The cap that goes from the regulator to ground.


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[m-Kresol]

you should go for the LM7815, it's possible that the 78L15 (TO-92) will not give sufficient current too. there's lots of ICs on the board. LM7815 and 78L15 also have In and Output switched, so have to turn it around (see datasheets).
as for the caps, I don't know what causes them to blow. Even if you've used 16V caps, those have to work with 15V although it's not ideal.

[jimilee]

Cool, I'll give that a shot. For now I've put it aside. When I get frustrated, things melt.


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