www.megadrum.info

Hi all

I have finished (finally) my megadrum, but i have a strange problem

When megadrum is connect with piezo if i turn on or off my ligh of room (or other room's) megadrum receive signal Note on


The same problem if i connect something in the power socket

I chek the voltage of my usb from pc, i have 4,96v, i have tried to change firmware version and to power the MD with external power supply (with regular 5v) and usb to computer but i have the same problem

If i don't connect anything ( no piezo or jack ) the the noise disappears

I see the pcb of my kit 3.2 synthex kit, the usb signal is controlled by PIC , is possible a problem of this ic's? (bad flash or malfunction???)

I have checked the GND is ok in all jack, no bad solder

Thanks a lot i will try to post a video

Electromagnetic interference. Make sure signal wires are well shielded and not extremely long.

Thans for the reply


The wires of jack are from flat ribbon cable, one side is crimping in a 40 pin connector, the other side is sold directly in a separate stereo jack's

The male stereo jack ( i have buyed the 3.5mm type) measure 1 meter, I think they are shielded

Have tryed with other usb port but this "electromagnet noise" is present... possible suggestions?


Thanks

put the megadrum in a metal box if possible. You may also have to use shielded jacks. This problem is usually caused older appliances, faulty wiring or bad grounding. Chances are, if you take it to a friends house, you won't have a problem.

Connect MegaDrum to a battery powered PC, e.g. a laptop running on battery. If you are still experiencing the issue than grounding/shielding is not good either on the board itself or on the input wires.

thanks Jman for your help, thanks dmitri for your reply

I have tried with old notebook (powered by battery) and the noise disappears, but if i connect the power supply (around DC 15v) in my notebook the noise note are present when i turn on or off the lamp/light or connect/disconnect something in electric courrent. This is for rooms where is placed the megadrum and in all room's of my house.

Actually i have megadrum in this box

http://www.elettronica-hobby.com/catalo ... i/TK10.jpg (container is plastic and 2 panel in alluminium)


It may be good idea if I cover the inside of the box with aluminum foil?

(yes, i should be careful not to create short circuit for the pcb)


thanks a lot and sorry for my english


( the kit i have is the old synthex kit v3.2 buyed from dmitri with blue pcb)

Maylord.war wrote:thanks Jman for your help, thanks dmitri for your reply

I have tried with old notebook (powered by battery) and the noise disappears, but if i connect the power supply (around DC 15v) in my notebook the noise note are present when i turn on or off the lamp/light or connect/disconnect something in electric courrent.

You may have problems with decoupling capacitors on the board. See http://en.wikipedia.org/wiki/Decoupling_capacitor

( the kit i have is the old synthex kit v3.2 buyed from dmitri with blue pcb)

You must be mistaken. I have nothing to do with Synthex's kits.

Hi Thanks for the reply

How do I recognize which are the decoupling capacitors on my board?

You can tell me the sigle? ( c1-c2-c3 etc..)

it may be useful i can take a pictures of my board for show you all the component's .


Thanks a lot for the help

All the capacitors which are connected to the ground and to +5 are decoupling.

Hi dmitri


I have controlled the pcb and i'm uncertain for 3 components ( capacitor )


I compared my pictures with the finished pcb of synthex

http://imageshack.us/photo/my-images/69 ... nthex.png/

This is my pcb:

http://imageshack.us/photo/my-images/82 ... citor.png/


The c8 and c14 in my pcb are ceramic (not polyester) , is a possible cause?

And the c12 in my pcb is ceramic and have the sigle 102 ( =1nf) , i see the quick manual and the c12 capacitor is 100nf polyester, is an error?

I have soldered the ceramic capacitor because I had not received the polyester in the kit.

I'm not expert but the difference from ceramic and polyester make this difference (noise in my case) ?

Shure, the c12 i will replace with 100nf (not 1nf)

Thanks a lot for the help