www.megadrum.info

I'm just getting my 2.7 board up and running. I fried the lcd due to conflicting data sheets from the same manufacturer. By the time I got it sorted out it was too late. New one is on order but in the meantime I'm flying blind.

I managed to get a newer firmware uploaded into my 644. My midi light comes on when I power up the board. Not normal right?

Now according to MCT and MidiOx, I have an orangutang beating on a huge kit when nothing is even plugged into the jacks. I managed to isolate it this far.

MCT says notes 26,36,37,38,41,43,45,46,48,49,51,53,57,58,62,63 are all going off at the same time with varying velocities. I pulled the 4 74HCs from the board and plugged it back in without them. Now only note 46 is going off steadily but at a low velocity.

I cleaned the flux off my board the best I could and had a look for solder bridges and breaks but didn't see any.

I verified that all my chips were inserted the correct way and that all my resistors were the right values.

I get the same results with nothing plugged into the board except the USB cable (no LED, LCD, jacks, etc.).

I will bring a multimeter home from work on Monday if someone can give me some things to check. I was pretty careful assembling the board and double-checked each component value several times before and after soldering. I went over the whole board with a magnifying glass afterwards to inspect my solder.

Did I use the wrong capacitor types in some places or does it matter? What about my crystal? MCT recognizes Megadrum and confirms my firmware version so that part works.

Pretty frustrated, spent all day trying to get it working.

Any help will be greatly appreciated.

Spugnoid.

spugnoid wrote:My midi light comes on when I power up the board.

It is normal for the LED to blink once during startup. If it stays on it means that there is persistent MIDI activity.

Are you using an inputs board or have you wired the input jacks yourself?

Also, there are 16 notes that are being falsely triggered. That might mean that two of your MUX IC's that you pulled out are responsible for your troubles. I would check the signal paths from the MUXes to ATMega. If there is a problem (e.g. a short) on a single MUX' output, it can erroneously trigger 8 channels at once.

The false triggering is occurring even with the jack interface ribbon cable unplugged. I am using Synthex All-In-One Board.

Other than an incorrect part value or a damaged mcu I just can't see what else could cause it with everything disconnected. I'm just running the bare board with no muxes inserted. Still getting one note triggering. USB circuit maybe?

Oh, at work I have the use of a scope as well if that will help.

My wild guess is that it is probably the hi-hat that is triggering. Do you have a hi-hat you can plug into it and see if that is the output that is causing the problem.

spugnoid wrote:Other than an incorrect part value or a damaged mcu I just can't see what else could cause it with everything disconnected.

If you can provide pictures of your board (from both sides) we might come up with more suggestions. Have you tried plugging e-drum pads in?

I don't have a hat pedal or any pads constructed as of yet. Does the board require certain jacks to have pads plugged in to function correctly? I went through all the inputs in MCT and disabled all the notes for each jack. Or does that only affect the output? I can try to get some pics of it and put them up here if you think it may help. I really hope I don't have to start replacing soldered components, I'm not very good at removing parts.

With all settings at default and without anything connected nothing should be triggering except maybe CC 04 messages for a HiHat pedal. If it is triggering then there is an electrical problem somewhere, e.g. short cuts, breaks, excessive flux and etc.

spugnoid wrote:I can try to get some pics of it and put them up here if you think it may help

Visual feedback can sometimes help very much.

spugnoid wrote:I really hope I don't have to start replacing soldered components, I'm not very good at removing parts.

It is not as hard as it may seem at first. If using a wick proves difficult, then there is always the soldering pump method. However, given the current description of your problem, my money is on shorts/flux related issues.

I hope these are not too large. Looking at the photo of the solder-side, are the tabs for the USB connector supposed to be soldered?

spugnoid wrote:Looking at the photo of the solder-side, are the tabs for the USB connector supposed to be soldered?

Definitely. Otherwise your 4 USB contacts' soldering joints (D+/-, +5V and GND) might eventually crack from the stress of plugging the cable in/out.