MIDI IN not working on Shruthi-1


My Shruthi-1 built 6 months ago has stopped today receiving MIDI message. I’ve tried with various MIDI interface (audio-to-MIDI via SilentWay, Prodipe MIDI interface, MOTU MIDI express 128) without success. The MIDI OUT seems to work, I’ve made a global sysex back-up from the Shruthi. I know how to solder and build, but I’m a newbee in electronic. The 6N137 is partly responsible of the MIDI ports, but I don’t really know what and how to check this problem ?

PS : I’ve spent my whole day with Metric Halo on-line support solving a boot states problem that crashed my MIO2882 audio interface. Today, the studio is a complete mess …

Thanks for your help !
Hédi K.

What is the voltage at pin 6 of the 6N137, at rest (no MIDI input), and when you send heavy MIDI traffic to the MIDI in?

With no MIDI event coming : 4,85V.
With a MIDI clip with a lot of notes and MIDI controller events : between 2,80 and 3,86V

This looks correct. No symbol on the Shruthi-1 LCD? The only thing I see would be a weak solder joint on the ATMega644P. This would be difficult to access, but you can try temporarily putting a piece of wire from the optocoupler pin 6 to pin 14 of the MCU.

I’ve tried it again and now the MIDI is working. I’ve also temporarily try to put a piece of wire from the optocoupler pin 6 to pin 14 of the MCU, it’s also working.

To say the truth, when you send me last March/April 2012 the PCBs for a Dual SVF Shruthi + ATMega644P + memory chip, the ATMega644P has a lot of damaged legs that I had to rescue. Maybe it’s not a bad solder joint but a bad contact with one of the damaged legs ?

BTW, I’m not saying that it’s your fault. :wink:

What happened to the chip/package?

I think that the package was a bit “over pressed” in transit at the post office (the 2 PCBs and the chips were packed in a “bubble envelope”). I’ve just discovered it when I’ve remove the chips from the foam base, a lot of legs were more or less flat … I will test again my Shruthi tonight.