Neovibe humming

[reeko81]

I've built my Neovibe, and i'm really astonished by this beautiful effect. It's liquid, it's like a song played through the water....but....
My neovibe is humming terribly in time with LFO. I've tested every ground point, tried also to link my neovibe without true bypass using the cancel switch and the hum is decreased a little but is still present.
It seems to be a ground ring that i'm unable to find cause i've also tested my unit with so much different adaptors and checked also my diodes bridge and 7815 unit.
What can i do else???
please! Help me!

[R.G.]

The first step is always to read the stickie posting "Debugging thread: what to do when it doesn't work" at the top of the forum list and provide that information.

In this case also provide the voltages before and after the 7815 regulator and whether you built it from a pre-etched PCB, etched your own, or did perfboard.

[R.G.]

The first step is always to read the stickie posting "Debugging thread: what to do when it doesn't work" at the top of the forum list and provide that information.

In this case also provide the voltages before and after the 7815 regulator and whether you built it from a pre-etched PCB, etched your own, or did perfboard.

[sfx1999]

Are you using an AC transformer? It sounds to me like the AC is being induced to your signal. When you plan to use AC like that, you need to twist the AC wires like a DNA strand and keep them as far away as possible from your signal.

[reeko81]

Thanks so much....i'll keep in mind to do a good dna strand!!

To R.G.
All values are good when testing after 7815.

[reeko81]

Bad news... No improvements....Also with that strand that ridicolous and annoying hum is still present.

I'm planning to use a dc 18 v transformer and to remove those 1000uF caps, diodes bridge and 7815 plugging the new transformer directly to the circuit.
What else can i do....??
Should i copy fulltone project, making a kind of wall between power circuit and neovibe circuit to insulate better from that hum?

PLEEEEEEEEASE HELP ME!!

[R.G.]

The Neovibe is not particularly hum prone.

There is a very common mistake that makes hum, but it usually causes smoke too.

Is your AC input jack grounded to the case?

Here's a way to figure out power supply problems: Hook two 9V batteries in series and disconnect the AC supply. Connect the two 9V's right after the diode bridge. Does it still hum? If so, you have a grounding problem, not a power supply problem. If not, you have a power supply problem.

The slam-dunk way to find ground hum problems (not ground loop problems) is to hook an ohmmeter to the input jack ground, then use the free end of the ohmmeter to contact EVERY SINGLE POINT ON THE SCHEMATIC which is supposed to be grounded. If that shows all points have continuity, you're good. If not, find what you didn't connect to ground.

And chill out. This is a trivial problem.

I'm planning to use a dc 18 v transformer and to remove those 1000uF caps, diodes bridge and 7815 plugging the new transformer directly to the circuit.

That's a bad idea. Use your 18Vdc adapter, but remove only the diode bridge. Connect the + and - from the adapter to the  holes where the + and - came out of the diode bridge that you removed.

[reeko81]

Excuse my poor english (i'm Italian), but i can't figure out how my AC input jack can be grounded to the case...
I'm using an insulated jack with tip and ring linked to those two diode bridge holes on the pcb.

To make my AC input grounded which is the correct link??

Testing with an ohmeter there's not any failed ground point....

I'm really an electronical dummy....
Pardon me