Neovibe slowes down when i put my palm over the board

[yeeshkul]

Neovibe slowes down its speed when i put my palm over the board, or when i put it in the enclosure. Otherwise it works great.
On what shall i focus? Any idea?

[ddpawel]

Connect your palm to the ground. It will solve the problem   

[yeeshkul]

That's the thing, the enclosure is grounded and it does the same thing. When cover the first part of the enclosure (with the circuit) with a lid, the speed goes down.

[ppatchmods]

does it have an ldr/led combo?

[yeeshkul]

ldr/bulb

[ppatchmods]

probably just some ambient light getting in there without it being boxed up.

[slacker]

That's what it sounds like, that shouldn't affect the speed though. The LDR's aren't part of the LFO circuit they're in the signal path.

[yeeshkul]

Yes, it must be elsewhere. Grounding of the enclosure is fine, voltages sit where the're supposed to.

[R.G.]

Did you use the modification which replaces the dual section speed pot with a single pot and an LED-dual LDR?

If so, it's light leakage.

[yeeshkul]

No i didn't. I took the PCB completely out.

The thing is:
- the fastest speed is pretty low now although i am using 2.4k in the LFO - "the speed mod"
- it doesn't raise intensity with the speed - it blinks pretty hard even at slow speeds
- I'm using a switching supply, i have not checked yet for a possible interaction of its internal pulses with the LFO

[Nasse]

some 30 years ago I did a drum machine with organ rhytm chip brain. Rock 8 beat was damn quite nice but then snare drum snare wires got malfunctioning state. It was playing bongo drum sound mixed with white or coloured noise for snare, and after few minutes noise stopped working. By placing my finger on board somewhere near gate transistor, it started again. It was not easy to play guitar while other hand inside drum machine. Can t remember if I tried my toe but found that if I did substitute my finger with a damp lump of tissue paper, I could use myu both hands on guitar again. Never got the noise generator fixed, but the wet paper trick worked for 3 weeks.

I have been thinkin there must have been a bad solder joint, some passive components not ok, cracks in the pcb, some transistor out of spec or design related things, some temperature related things, or power supply problems (it was not really designed for 9 volt batteries but thats what I had to use). Plan b was to make totally new external noise generator but then I zapped the rhytm chip which soon went obsolete

[yeeshkul]

Reheating didn't help, a non switching power supply 24V didn't help, so I finally changed Q11/12 and the three 1uF caps and the thing started working.