USB midi signal lost possibly due to electrical noise

[dmitri]

Replacing R22 of 3k3 with a 1k res does not make a difference.

Are you sure you're using my firmware?

[Firelord]

Yeah, the one that's 'recommended' in the download section.

[Firelord]

I've also found this document that should probably shed some light on the problem at hand.

http://ecee.colorado.edu/~mcclurel/iap125.pdf

Damn, I would like to blame this one on the flux. But you can't blame flux for every trouble that you have, can you? Anyway, we have another fact from this topic that when the analogue board is disconnected, no noise is generated. Also, no one with a Synthex kit reported in. In the document above I'd stumbled upon one interesting thing called 'Ground noise' (among other possible noise related problems). Could this be it?

[dmitri]

1. Try lowering R29 to 10k-1k.
2. Try another crystal.
3. Try resoldering all solder points.
4. Try another PIC.

[Firelord]

I've done another test. This time I disconnected the analogue board and used MIDI-OX to monitor MIDI messages from MD in Fw Updater mode, pressing the left key. No noise was generated (obviously) and the USB connection was stable during this test (I was continuously turning the soldering station on/off).

[Firelord]

1. Try lowering R29 to 10k-1k.
2. Try another crystal.
3. Try resoldering all solder points.
4. Try another PIC.

I'm afraid this will not do any good. I'm convinced (at the moment, at least) that we have a grounding issue here. I will do some more testing later (next week maybe?) and come back with the results (hopefully).

Thank you for your support

[Firelord]

With the analogue board connected in Fw Updater mode the USB connection was lost during similar testing.

[dmitri]

...
3. Try resoldering all solder points.
...

...
I'm convinced (at the moment, at least) that we have a grounding issue here.

resolder all soldering points leading to the ground.

[Firelord]

resolder all soldering points leading to the ground.

Even though I'm new to manufacturing printed circuit boards, I'm quite sure my soldering is quite solid (before assembling MegaDrum, I've checked that several times). Besides,

1. Two people share the same problem (and how many of MD users assemble MD from scratch using the two board desing anyway?);
2. Even when I unsolder the ground wire on the analogue board (i.e. there is NO connection between the analogue board and the jacks) I still get this problem.

Thus the issue lies somewhere else. Of course, it may be some dumbass mistake (like in the case of the conductive flux), but it is not THAT obvious, I assure you. My money is still on ground noise. I would assemble a new analogue board with 4851's without the resistors/bat85's (to compare the circuit behaviour), but I do not have the resources right now. This becomes rather a personal challenge, and I will do my best to find a cure for the situation.

[dmitri]

resolder all soldering points leading to the ground.

Even though I'm new to manufacturing printed circuit boards, I'm quite sure my soldering is quite solid (before assembling MegaDrum, I've checked that several times).

It's not about soldering skills. Resoldering can eliminate hard to see loose solder bits and may spread some excess flux. I do it myself sometime.

I would assemble a new analogue board with 4851's without the resistors/bat85's (to compare the circuit behaviour), but I do not have the resources right now. This becomes rather a personal challenge, and I will do my best to find a cure for the situation.

Does the issue go away without the analogue board connected?