Just 2 little problems to solve and i'ts done! (Solved!)


I just finished to build Shruthi-1 pack. The Voltage, leds and sound test are OK.

But I have two little problems:

First i don’t understand how to ajust contrast to LCD screen, i turn in anti-hour direction for a long time (2 hours) and the screw was never stopped. So i try in another direction (less time) and nothing change. I can see dark blue cases in middle of united blue.

My second problem is a little noise with a high frequency at audio output, it’s my first project can you tell me what solder i need to check cause i’m not sure what is a good or bad solder.


Ps: Sorry for quality of English…

For the LCD: the screw doesn’t stop but you can hear a “click” when it has reached the end. Try turning 20 turns or so in one direction, the in the other. If you can’t see anything, try resoldering the trimmer.

For the audio whine: have you tried another power supply?

Thanks for your speed answering! The problem was power supply and now no noise and screw ajust contrast! I’m so happy!

There is a last thing i can’t do is midi in notes by Logic Pro 9. I use a Mbox 2 soundcard, i configure it on port 1 ( i haven’t choice), and put it on all channel in my software and select channel 0 On Shruthi but no notes are coming.

It’s can be possible that i do something wrong because it’s my first hardware who i connect in midi. But in order to be sure can you tell me how chek midi is correctly solder on Shuthi?

Do you have scope? Probe pin 6 of the 6N137 and you should see a level +5V with dips at 0V at each bit in the MIDI serial stream.

I have no scope, only a multimeter, for testing the Shruthi-1 need power supply? How find pin6?

“and you should see a level +5V with dips at 0V at each bit in the MIDI serial stream” I don’t understand.

And i’m not sure to put 6N137 on the good side. The dot on 6N137 is looking in opposite direction of the notch at the top of the chip. I’m scary to change the side cause i know nothing in electronic and i don’t want to burn something…

I’m sorry to boring you with my basic questions but i’m lost in this field.

Please read the foum rules, only english here . The goal of this forum is to help each other and you won’t receive much help if most of the people here cannot understand what you have posted.

You won’t see fast MIDI signals with a multimeter ; that’s why it’s better to use a scope to troubleshoot such problems. In any context, voltage measurements should be done with the circuit powered on ; continuity measurements should be done with the circuit powered off.

You have put the 6N137 backwards; the dot should be on the same side as the notch at the top of the chip.

Yeah it’s working! Thanks for all and good week!

ps: Sorry for french, i translate my previously post :wink: