testing megadrum input pins

[gkurtenbach]

I'm wondering if maybe I"ve got malfunctioning MD. I re-wired my input wires but after that the wrong inputs were triggering. I traced all my wiring and it seems correct. So I reduced my input connections down to just the kick trigger: pin 4 for the kick tip and pin 40 for the ground. That produces kick triggers but there's lots of random triggers so I have to have the threshold much higher then before. It seems like there's something wrong.

Is there some way that I can test the MD with the input ribbon cable removed? For example, if I touch pin 4 with a screwdriver should the kick input trigger? Is there a way to test trigger the input pins?

thanks,
Gord

[dmitri]

For example, if I touch pin 4 with a screwdriver should the kick input trigger?

It should.

[maakassander]

I didnt want to make a new topic.

I have a few questions. I have built 2.5 all in one version of this project. It uses atmega32 without protected bootloader(silly me that i didnt figure it out before ordering parts that i can only use 2010 firmware with that).

I programmed the chips via ISP and ISCP cable. I got latest unencrypted on atmega and i think i got the firmware for pic from the download page(i just dont remember). I got it working all good. if i touched the pins, i got LED flashing VU meters working and usb-midi activity from every pin it should come from. But now that i have time for that again, it wasnt that good. If plug my MD in, the device is connected and then disconnected and reconnected and so on.(it has happened a few times before too actually). It sounds like a bad solder somewhere, doesent it?where can it possibly be? Or is it that resistor from pic to gnd and suitable firmware thing? Is there anything else it can be caused by?

So now to atmega. I touch the pins, no movement activity at all - no vu meters no led. I accidentally discovered, that if i get connection between these jumpers just above the 4 chips and one of the input pins, i get led flashing and vu meters moving. i once got even midi activity in midi-ox just after i connected it to computer and it hadnt disconnected yet. This sounds like bad solder somewhere too, huh? But where should i search for it the most. Can the atmega problem be caused by this pic problem? I dont think it can be vice versa.

Any recommendations? i'm afraid to screw something up trying to repair it all by myself

[dmitri]

Synthex 2.5 PCB is so old and it is not compatible with the latest PIC USB firmware that I suggest you to re-build it using viewtopic.php?f=3&t=1623 or viewtopic.php?f=3&t=1075

[ignotus]

Dmitri, I use an even older Synthex pcb design with the latest PIC firmware and it works fine. I reckon the connect/disconnect problem of the PIC is related to the pullup resistor for the PIC (22k - 47k from pin 26 to ground). I had the same problem and that resistor solved it. As for the Atmega problems, that's anyone's guess... All I can say is check/re-check all connections with a multimeter. If it first worked and then stopped working, chances are that a connection somewhere failed.

[maakassander]

Well, i soldered a 47k resistor from pin 26 of pic to gnd and the problem is gone. Did a lot of resoldering near input and now it's working all good. Feels good, heh Now i just need to find an enclosure and some piezos. Thanks for advice!