Noise on faders

[Arkadiuz]

Hello there, I'm having problems with noise on the faders, and actually it may be an interesting problem:

The device is an Midibox LC, but with some hardware and software mods, not big deal. It doesn't have ledrings, and no motorfaders. Just regular cheap generic 10 KOhm faders. It uses 4 DINx4 modules, 1 DOUTx4 moudule, and a Core32 module. Also, a GLCD T6963 240x64.

The tact switches, encoders, leds, and faders, are all placed on custom PCB's designed and made by me, not a great work, but if anybody interested on the sch and pcb, contact me!

All boards and signals are connected by 5 pin ribbon cabe. There must be like 25 cables like those. The faders are connected directly to the Core32 board. The LCD too, but with a 20-16 ribbon cable.

So, the MBLC is working, I tested it with Cubase SX, and works like a charm, except for the noise on the faders. I get random noise, one channel at a time, then it hits any other channel, and other and so on, small changes though, but pretty annoying when using the 'solo' function.

• I tried lowering the AIN resolution to 4 bits, and didn't work.
  
• When the project is in 'Stop', there's no noise.
  
• When you hit 'Play', there comes the noise.
  
• When you unplug the LCD cable, the noise goes out and works perfect, except the LCD :S.
  

So, I think the LCD cable (25 cm long) is causing the problem, but don't know hot to solve it.

Update:

[ Tried to power the boards with batteries + 7805 but the noise is still there.

I don't know man, this is like black magic :-S ]

Any tip?

Edited December 13, 2010 by Arkadiuz