Shruthi-1 midi problem

Hi there,
I finaly assembled shruthi-1and it worked for like 30min and than all of the sudden midi stopped working. If i hold first button shruthi is generating sound, but is not responding for any midi keyboard ( i’ve tryied 3). It was working well, but for 30min. Any solution / similar situations ?

Maybe you’ve changed the MIDI channel the unit is receiving on? (by default it is 1).

Check that the optocoupler (6N137) is correctly inserted. You should read +5V on pin 6 of the chip at rest ; and this should drop down a bit whenever a MIDI message is sent (use the modwheel on your master keyboard to send many MIDI messages and observe the voltage drop).

Is the note symbol flashing on the LCD when you press keys on your keyboard?

Midi chanel i’ve checked many times, same with optocoupler. I will check that 6 pin, and let you know

No note symbol : /

on pin 6 of 6n137 i have, +0,60V and nothing changes when i pressed key or pitchbend or modwheel

There is something wrong with the optocoupler. Check that pin 5 is continuous with ground ; and that pin 8 is at +5V

both are correct

8 pin is 4.9V to be exact

I can’t buy new 6n137 untill monday, i have 6n139 would it worked also ? What could be the reason that it was working and that it stopped ?

I had the same problem with my first shruthi, I forgot to solder some pins on the midi connector, so contact was uncertain …maybe you could check this

Hard to check now there is a LCD blocking view, but im rather shure that i solder all pins. Maybe somebody has a map with pin is going where than i could check if there is connection

I know that pin 2 of midi In is going to 220 resistor and that’s correct, 4 pin going to 3 pin of 6n137. How to check the rest ?

Schematics are here
Pin 5 to Ground
Pin 6 to ATMega pin 14
Pin 7 to nothing
Pin 8 to Vcc

All correct both midi && 6n137, what else could be wrong ?

Do you get fluctuating values before the 220 on the MIDI in when moving the pitchbend or mod wheel? Since you don’t get anything on pin 6 my guess would be faulty opto coupler as the resistors rarely fail.

Pull the IC out. You may have a folded leg?

Legs are on right positions :slight_smile: I will wait till monday and replace optocoupler. Meanwhile thx for involvement and support

I replaced optocoupler but nothing happen, still no midi :frowning:
What else could be wrong ?

Do you still see the same readings?