4 Pole-mission : Power test looks like bad

hi, i finished to build the cards of my shruti 4 Pole mission, but i failed for the power test.

My power supply is : http://ca.mouser.com/ProductDetail/Xicon/412-112034/?qs=0rR3T3h2KM9HrCJzDLTMPw%3D%3D

pichenettes says :

Please create a new topic and post the voltages at each pin of the regulators. Which point do you use as ground?

i don{t know how to mesure on the regulator, but the power test results are :

green-red : 9.5V green-blue : -9.1

i didn’t sold any led at the moment is it important ? i also used a 100V for C30 cause i couldn’t have the part at the moment.

I did something wrong ?

Thx to help me !


First, check the audio signal on the 4 points! Looks like you haven’t posted any audio sample of it…

ok, and so what i could try ? changing the IC5, buy a oscilloscope, pray god to help me ? :slight_smile:

I assume the meter is in DC mode? Then you’re measuring the DC offset (average) of the audio signal, which should be null. But it doesn’t tell you if the signal in itself is null. That’s why multimeters are pretty useless for troubleshooting audio problems!

hello, sorry for this long silence, but the weekend was quite hard for the canada national day ! :slight_smile:

to mesure the 0V, i use the black probe of the multimeter on a ground point like the green point of IC1, and the red probe to the point 1 2 3 4 showed on the assembly order.

just after the job i will listen and record what happens on each pole.

ok, i mesured 0V at the 4 pole. is the IC5 fried ?

What did you do to measure 0V?

Have you tried listening to the signal at those points?

Up! (to work on it this weekend ! it’s raining !

Yes, check the sound at the 4 points highlighted in the documentation. The signal level there are at least 1V pp so it should not sound low on your mixer/soundcard.

ok i resold some point, now the resonance look likes to work, but i have again some problem ! (1 less now)
I don’t see any changement when a change the type of filter
The sound volume is really low
i have some crack on the sound (linked to the volume i presume)

Do you need the same mesurement as precedent ?

i’m on the good way !

ps I just want to thank you Olivier (and the others), you’re nice to help me ! Bye and thanks again

yes, the synth work with the LP1 mode. i will gcange all the components around C4 and C5 tonight.


Can you check that the synth works with the filter set to LP1? It looks like only the first pole of the filter is working.

This would mean a bad soldering on IC4, the 2 capacitors above it ; or any of the resistors above IC5.

ok, i do it !

Like each time C4 to C5 in loop with filter at 127, resonance at 63, env at 32 and lfo at 0.

pin1 of IC1 – Soundcloud
pin1 of IC4 – Soundcloud
pin7 of IC4 – No sound
pin7 of IC6 – No sound
pin1 of IC6 – No sound
pin8 of IC2 – Soundcloud

So there is no sound for 3 of the pole filter…

Everytime if i touch one time the resonance, it sound like the pin8 of IC2.

I you need more things, ask me :slight_smile:

Have a good night or wake (it is early in France now , so have a nice breakfast )

Thx, Bye

yes i will do it, i have jyst some questions, to do it i have to use a jack with 2 probes on the other side. i have just to connect it to my sound card and record what it happens ?

Thx bye

Yes, the probe connected to the tip connected to the point you want to probe, the probe connected to the sleeve connected to the ground.

If the sound level is very low, there’s definitely something wrong on the filter itself, and maybe on the VCA too.

A few messages back I have asked you to check the following signals:

pin1 of IC1 – raw oscillators signal
pin1 of IC4 – pole 1 of the filter
pin7 of IC4 – pole 2 of the filter
pin7 of IC6 – pole 3 of the filter
pin1 of IC6 – pole 4 of the filter
pin8 of IC2 – output of the pole mixer

Please do so! If the filter does not work properly, you should hear a massive volume drop between pin1 of IC1 and pin1 of IC4.

Up !

ok, after mount it, the problem persist…

ok, i explain you what i do :

1 - i plug it
2 - I launch FL Studio and playing some note without touching anything on the shruti-1 note C4 D4 E4 F4 G4 A4 B4 C5
It sound that : Souncloud . The sound is a bit low, but not too much.

3 - i put the cut at 63, the res at 63 the env at 32 and lfo to 0
It sound that : Soundcloud .

So i’m sure it’s the resonance circuit who have a problem. The Ics are a bit warm, but not too much.

also if a change the type of filter, it’s don’t change, i sound each time a lp, but not a hp.

I know i’m a newbie, but so much things sound really strange, i feel sad… i want to use it properly

Thanks for the help, Bye

no, i just put a note on the FL Studio sequencer and let it for 15s. no the pitch don´t change (But i will try another try again tonight cause each time it did something different !

I that the regualtor are quite hot, i don´t know for the ICs, i will mesure it tonight.

I will also record another sequence with sound tonight to see if the Shruti do the same strange sound.


Is that the sound you get during boot? Does its pitch change with the note you play? Is there any of the ICs getting warm?