Kingslayer, really hot ic's and high pitch whine.

[jolly1423]

So I built two of these and wow, amazing pedal. Mine has been working great but the one I built for a friend worked great for months and then all of a sudden it has this awful high pitch whine when engaged. I checked it out and noticed the ic's are getting super hot, almost too hot to touch. Any thoughts on that, has anyone seen that before? 

[jimilee]

What do your voltages look like?

[jolly1423]

1-.57      8-.85
2-.35      9-.68
3-0        10-.59
4-8.67   11-.46
5-0        12-.7
6-.55     13-.72
7-.69     14-.76

1-8.63            5-8.57
2-4                6-8.39
3-.01             7-8.17
4- neg. .11     8-1.02

8.71v going in

[madbean]

Make sure your charge pump isn't backwards (I've done it) or your electrolytic caps.
You should be reading -9v on pin5 of the charge pump. It may need to be replaced.

[jolly1423]

I double checked everything with polarity, it's all the correct orientation. It seems odd to me that it would work great for 6 months and then not. It would suggest to me that something from the outside world affected it, i.e. a surge, but I know the guy has been powering it with a Pedal Power 2 so that seems unlikely.

[jimilee]

You may want to start with the electros perhaps? Sound Somme like a surge as well. Are the electros rates above 18 volts? I built a pedal that has a charge pump in it recently and pretty sure I put 16 v electros in it and often wonder what is going to happen.

[jolly1423]

They are all 25 or 50v except C23. Think that's the culprit?

[midwayfair]

They are all 25 or 50v except C23. Think that's the culprit?

I'd sooner suspect the charge pump and the Zener.

If your friend decided to see what happens when he powers the pedal on 18v, he could have blown both. The Zener would short to ground and then all your ICs would get hot, too.

[jolly1423]

Well, he says he only ever supplied 9v from the voodoo labs, maybe a wall wart once. He's a pretty honest guy. I think I'll just start by replacing the ic's, the zener, and C23 and see what happens. Thanks for the help thus far guys.

[jolly1423]

Is a tlc274acd going to be the same as tlc274? Smallbear has that one...don't recall where I bought them before. I think Mouser which is numbered tlc274bcn.

[jolly1423]

So I replaced the charge pump, no difference but replacing the tlc274 fixed it. I don't know what the deal was so I replaced the 9.1 zener and upgraded C23 from 16v to a 50v as a precaution. We'll see if it happens again! Thanks for your help guys