Anushri - just built but no midi input

Hi all,

I have just completed the Anushri build and all is working fine. But I can’t get a note playing from the MIDI input. I’ve checked the midi signal with my Struthi and its receiving. Its in synth mode and I’ve tried to detect the incoming MIDI as described in the manual… I’ve checked the MIDI connectors and they appear to be soldered correctly…

Any hints on how to debug this ?

Best wishes

i guess you put it in the correct midi socket? (not trying to be super smart ass but that can happen. i also managed to swap pins when i soldered the midi sockets off board, just as an example)

What is the voltage on pin 6 of the 6N137, at rest, and when you send a lot of MIDI messages?

Thanks for the advice guys … I’m not having a good start to the day. To furnish this thread with some more information… Last night upon completion I had the drum machine working, and I could activate the drone on the synth by holding HOLD… all knobs and buttons appeared to work fine. Everything apart from MIDI input issue.

This morning, I checked all the solder points, however I may have put the 6N137 IC in back to front. Now I find the unit isn’t really powering up successfully, its random, sometimes the LEDs come on, sometimes they don’t… I certainly don’t have the level of functionality I achieved last night. When it powers up now, I dont even have the drum machine or drone from the synth.

Its currently sat here, powered up, with all 6 LEDs on. but it doesnt respond to anything.

So, my issue seems to have got worse


@ rest = 0.429 v approx
with MIDI = 0.46 - 0.49v

Now please bear in mind I am by no means proficient in checking with a multimeter… but these are my results

Remove all the chips except the LT1054 and do the voltage test as described in the build instructions page.

ok thanks, will do it now

I removed all the chips, and after a few minutes of testing voltages as described in the instructions, and getting values nothing like those described , it appears the psu has damaged and now doesnt power up…This is a similar case to another thread on this forum. I hope with a new psu it’ll power up fine…

Make sure you put them(chips) in the right way, and be prepared that some may be damaged :confused:

I would take the time to take a closer look at your board, there’s a good chance that there’s a not entirely good solder joint somewhere :frowning:

I just found another psu in the office, its a 7v dc… i connected it… and done a quick voltage check like the description and the values are pretty much spot on… I’m putting the ICs back in now to test

chips in, powers up… and drum machine working so far

drone working… can tweak the filter, resonance and pretty much everything it seems … I’ll check the 6N137 for midi data

it appears that the DCO is working and not VCOs… ie it only make a synth sound when sub is set to DCO…

Ok guys, heres today update.

I’ve got the board powering fine on 7v psu… Its the only one i have in the house for now until next week. … The VCO is not functioning. I can only get sounds when sub is set to DCO… the filters, lfos, amp env all appears to work fine… the drum machine also works fine… all pots appear to do their job, except ofcourse anything related to the VCO, which doesn’t fire a shot… The MIDI input isn’t functioning also, I have checked with a number a MIDI sources, and nothing…

the voltage for the 6th pin on 6N137
resting = 2.17v / varies
with MIDI = fluctates a little, but not precise

could someone be so kind as to have a look at these results and give me some leads on how to solve this problem. I have little electronics experience, however I did successfully build the Struthi… I have a decent multimeter here and a pretty good scope but I have little experience using the scope… so if further tests are required that involve using the scope, please give me some advice on that…

I’ve done the tests and here are my results

1. 7.16v
2. 6.36v
3. -5.61v

Red points are all coming in at approx 4.9v
Green point -4.9v
Purple Points **** not quite sure where to check here…, left or right pin ??
Cyan Point -4.13v

A. Seems fine, when i move pitch up and down using one of the knows, the votage goes up and down… appears ok
B. Again, seems fine, when VCF is modulating, the voltage goes up and down…
C. Seems good… at rest is ov… when drone is on = 1v , when sequencer is trigger notes = 3.44v approx
D. Hard to get a reading, appears to fluctuate alot.
E. doesnt fluctate , stable at 4.88v
F. 3v stable
G. -3.33v
H. -3.34v
I. -4.89v
J. -4.89v
K. 0.918v
L. Fluctuates, appears fine…
M. N. O. Filters appear fine, will self oscillate if needed.
P. Fuzz appears to work fine.
U. 2.44v
V. 3.71v

Regarding MIDI, resolder all pins of the optocoupler. Some more checks:

  • Pin 5 must be continuous with ground.
  • Pin 8 must be at +5V.


I resoldered… pin 5 = 0v pin 8 = 4.9v

Is pin 5 continuous with ground? It’s not because the meter shows 0V that it is continuous with ground.

How can i confirm this ?

With the meter in continuity testing mode.

Thanks for that… Yes, pin 5 is continuous…