neovibe humming badly...

[swt]

HI. I try this as the last chance. my neovibe is humming badly in time with the lfo. As a tube amp builder...this sounds a lot like a bad grounding, but didn't know that can happen in small signal and pedals. It's a pcb from geo/ggg, p'n'peel, it's working, but highs are really subtle, if this is a clue. if i turn the depth pot down, the humming goes down also. have already checked archives, and search function. Any clues??. bc549b transistors, 2n3904 for lfo and driver. pinout is correct.

[Aharon]

I built the NeoVibe and it works flawlessly as have others so I would look for a bridge between traces (PCB is tight) or a wiring mistake.
I used shielded cable for input and output.
Aharon

[petemoore]

 my neovibe is humming badly in time with the lfo. As a tube amp builder...this sounds a lot like a bad grounding, but didn't know that can happen in small signal and pedals.
  Have you clipped the DMM lead to ground and checked all grounds from that point?
It's a pcb from geo/ggg, p'n'peel, it's working, but highs are really subtle, if this is a clue.
  if i turn the depth pot down, the humming goes down also
  If my guess is correct, this pot pans between taps in the circuit [mixing clean w/phased signals?...] the humming decrease may be in the part of the circuit which 'that side' of the depth pot is connected to.

[KHStudio]

I'm having a serious HUM problem too. I'm using an external 16v AC wall wart, about 300ma... is this enough?

Grounds seem good.

When I put the lid/bottom cover on it gets MUCH WORSE.


Any ideas. The pedal is done & sounds GREAT exept for this issue.

Thanks,
Kevin

[swt]

more reports...i'm building a new one on perf, as usually do with everything else. on the one with problems, the hum is on the vibe side, the clean in ok, but chorus and vibrato gets affected by the lfo humming. strange thing...if i use the original cancel switch, the hum is gone. sounds like a reversed electro, but checked everything, and looks alright.
Any points worth checking with an audio probe??. voltages?. Thanks!!

[iron25]

I recently completed R.G.s neovibe project.<sounds killer>
In the tweaking stage now.
The hum problem, in my case was due to the power supply I was using.
18V ac 1000ma, purchased from a national chain, just a cheaply made product I suppose.
Dug out an old 18V DC 500ma, and the hummmmm is gone.
Try a different power supply if you can.
If that dosen't do it, list your voltages here and I'm sure something will jump out to one of the fine folks who frequent these boards.
Thanks again R.G.!! 

[KHStudio]

Well, if I try a DC supply - what components SHOULD I remove from the board?

Also, How would I arange diodes in place of the diode bridge?

This hum thing is driving me nuts It's pulsing with the bulb & gets worse with the cover on... not as bad outside the case.

Thanks,
Kevin

[iron25]

I wasn't really suggesting a DC as much as just a different power supply.
I happenend to have a DC that was in V range.
Here's a quote from a post I found from R.G.~

As to AC versus DC from the wart: The PCB is designed for an AC input, like the original. If you use a DC input, it will always be "rectified" to the proper direction by the rectifier bridge, so as long as the DC or peak AC is on the order of 18-24V, it will work fine. Note that this is 18-24Vdc and 13-15Vac because the peak value of the AC waveform is bigger than the RMS value that's quoted in the rating.

If you use a DC power supply, you must choose whether to use an isolated DC power jack or not. Because of the rectifier bridge, you cannot use a nonisolated power jack and the on-board rectifier bridge at the same time. You must either use an isolated (plastic busing style) power jack or else remove the rectifier diodes from the board and connect + to +DC and - to -DC from the power jack. Using the rectifiers and a non-isolated power jack simultaneously will result in overloads on the wall wart and some release of smoke, as well as another string of questions here.