Shruthi-1 no midi

Assembling my Shruthi but it is not responding to MIDI, have checked for voltages on OK1 but pin 6 shows no discernable difference when MIDI signals are sent. Have removed lcd and checked all solder points and all seems fine. What should I try next?

is pin 5 of the optocoupler continuous with ground? And pin 8 at +5V? Is the diode near the optocoupler correctly oriented? And the optocoupler itself?

Yes to all of the above.

I have also checked my MIDI set up and it’s fine, I’ve tried three different controllers but nothing happens. Pushing button 1 does produce the test tone and I can toggle through presets and even accidentally started the sequencer somehow but can’t play with my keyboards or MPC. Puzzled.

I was going to say is the chip inserted backwards or is it the wrong chip? ( thats what i did )

No, the chips are correctly oriented in the correct sockets. Quadruple checked twice. Should it matter that I’m using a regulated power supply?
9v 500ma?

yes that should be fine. have you checked continuity between MCU pin 14 and 6N137 pin 6? (the actual pins)

You should have look at that tread named : No sound, no midi, LCD weird (SOLVED)
from dec 2. to the end

Will try that after dinner thanks rosch.

Aha. No continuity. Yes on the soldered side, no to the actual pins. Socket maybe?

could be the solder joint or the contact from chip to socket, maybe resolder the joints and put the chips in one more time.

Tried to remove 6N137 from it’s socket and only one side came out, pins 1-4 were stuck and in trying to wiggle it free I can see a fracture in pin 2. Doh. Guess I’ll have to ask for a new one. Think it is probably best to replace the socket too. Seems likely this may solve my problem. Hope so, I’m eager to get playing this thing it sounds amazing.

Ok, finally got back to this after various celebrations and illness. Replaced 6N137 and it’s socket, I have continuity between MCU pin 14 and pin 6 (actual pins) but still no MIDI in. Have checked with various working controllers. What should I try now?

are you sure you midi setup and midi cable is 100% ok?

Check for continuity from MIDI jack pin to pin on the PCB. I made the experience that sometimes they look fine, but just to fool you…

1000% sure about cable, using it just now to run another synth. Have tried many cables and different control keyboards and sequencers. Will try checking that nightworxx, thanks.

Are you still unable to observe a voltage change at pin 6 when MIDI data is sent? Stuck at +5V?

Back again. Yes, pichenettes I’m stuck at 4.98V. Wiggling the pitch bend about and nothing. MIDI socket to PCB all test ok nightworxx. Audio out ok. Had shruthi sequencer running again as well. But no MIDI in. What should I try next?

Sorry for the long time between posts by the way, I have been a bit unwell recently and not able to work on my shruthi. Ready to try again now though. Any thoughts?