New build shuthri - No MIDI, everything else perfect


I built my shuthri the other night, it took me about 4 hours and it seems to be fully working except midi is not working. I’ve tried flipping the 6N137 round to make sure it’s not the wrong way round and that didn’t fix it, and I swapped it with the eprom to make sure that wasnt the case and that just made the shuthri not turn on.

The only thing that happened in the build was I didn’t realise the mosfets were different and I accidentally had them in the wrong way round. I was trying to get it finished in one evening so I think I was sleepy/not reading properly.

Could I have somehow broken the optocoupler? I’ve reseated it a bunch of times, I’ve reseated the AVR a bunch of times, and I can’t get the midi notification note to pop up on the screen, or any notes to be triggered via midi.

pictures of the build are here I can take some better ones after work when I am back home again. The LCD screen is on the unit at the moment but I have a vacuum desoldering station so I can take it off pretty easily.

i’ve ordered a new 6N137 just to see if that is a magic fix. everything else works though, so it must be something in that little bit of midi circuit - I haven’t yet probed it as I need to take the LCD off to get access I’m just fishing for some ideas to try tonight when I get home.

thanks for all your help.

You could probe and add some solder from the other side of the PCB, so you can do some tests without removing the LCD, see this thread (Yeah, I’ve had some problems with the MIDI too, and still haven’t had time to fix that.)

Thanks i’ll give it a look.

looking over my pictures I can’t see anything I haven’t soldered and all the joints should be fine.

it’s annoying haha, I want to make the sweet midi triggered sounds :slight_smile:

I just glanced over your pictures, but I couldn’t see anything blatantly wrong around the components belonging to the MIDI path. But a second, more experienced opinion might be good. My MIDI In works sporadically and I have a hard time reproducing the error, so I’m a bit annoyed too :slight_smile: I also happened to fiddle a bit with the optocoupler, bent a few legs, and now I have to order more before moving on. Sigh…

this is it - I don’t know the state of the optocoupler, it might be janky I don’t know.

I don’t think there is anything up with the soldering.

I read somewhere about having the 2 resistors the wrong way round by the optocoupler so maybe I’ve done that - I don’t really know without probing it.

Perhaps you can take a high-res image of the area around the optocoupler (both sides of the PCB) ? There is not much to deduce from the images in the link you provided …

I will take some pictures with my DSLR tonight with the LCD off and see what goes - thanks for your help. I appreciate the build images are rubbish, just snapped on my phone to document the build.

Don’t take the LCD off just yet (a pain !) - perhaps first post an image of the ‘accessable’ side of the PCB.

high res pic of the available side attached :slight_smile: excuse the fluxy board, I haven’t cleaned it yet.

EDIT: am I right in thinking those resistors are the wrong way round ?

EDIT2: I’m definitely sure that’s what up now I’m using my eyes :smiley: hmm, now how to swap them round… infact I’ve got all 4 resistors there mixed up

Yes, R18 and R19 should be 220 Ohm (you have 10k Ohm there)
R1 and R14 should be 10k Ohm (you have 220 Ohm there)

Edit: you have a desoldering station but not a multimeter? :wink:

Fixed now :slight_smile: apologies for stupidity!

I have a multimeter hehe, I’m just sometimes stubborn to use it! (and quite blind apparently, shouldn’t build electronics late at night after work)

Great to hear it was just the resistors - not too hard to fix (as you’ve done).

Enjoy MIDI in then !