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 !

  • the 100v voltage on the caps are no problem. these are maximum values. so no problem with your c30.

    your voltages are to hight. the regulators are not doint their job.

    please check all solder joints of the power supply: caps, regulators (7805 and 1905), lt1054.

    look at the build instructions of the SMR-4 the power supply is the same as on the 4-Pole board the components are placed somewere else though.

  • Measure the voltage at each pin of the regulator.

    They are labelled O – I on the 7805 and O I + on the 7905

  • OK, i mesured the voltage at each pin, but i didn't know how to mesure correctly.

    7805 :
    - o : 9.1V (black of the multimeter on - )
    - I : 14.2V (black of the multimeter on - )
    o I : 4.9V (black of the multimeter on o )

    7905 :
    I o : -4.9V (black of the multimeter on o )
    o + : 8.7V (black of the multimeter on o )
    i + : 13.8V (black of the multimeter on I )

    Something is wrong ? what i have to do ?

    Thx for your answer ! Bye
  • The black probe of the multimeter should be on a grounded point.

  • ok, so i took a green point From the test to mesure. (IC1)

    7805 :
    o : 9.5V
    - : 0V
    I : 14;6V

    7905 :
    o : -9V
    I : -14V
    + : 0V

    Maybe it's a regulator problem ?

    Thx ! Bye
  • It’s strange because this indicates that both regulators would have failed – it’s rare that this happens at the same time! Do you trust your meter?

  • yes, i trust my meter, it´s new (maybe i do something wrong with the selected Voltage.

    i mesure at 200V, in continue (top line in little pointed line, and bot line continue)

    must i change the 2 regulators ?

  • Yes, you could try changing the regulators ; though I still find it very suspicious that both of them simultaneously failed…

  • What a minute, you measured 200V somewhere in this circuit?

    I’m new to this, but I’m pretty sure if the board is getting 200V that is enough to fry some eggs.

  • He means the 200V mode on his multimeter.

  • @6851punk – :-\

    The first sentence says “so i took a green point From the test to measure. (IC1).”

    I wonder if the black probe isn’t grounded properly?

  • That’s what I though too, but – and + are the ground points of the regulators, and they appear at 0, so the measurement has been done with a correctly grounded probe.

  • ok, i will change the regulator, and we will see...
  • What happens if you reverse the polarity of the electrolytics that are in the power circuit? Or mix them up? C31-32, C37-39?

    I don’t get how he gets 9V out of the regulators.

  • If there’s a short somewhere then the input voltage could be bypassing the regulator.

  • Sorry if I am adding to the confusion… trying to sort these things out helps me learn too.

  • anyway, a multimeter in 200v DC mode is going to be pretty far from precise when measuring a voltage in the likes of 9v or 5v. Can’t you change the voltage limit so you can get something more accurate?

  • ok, i have to wait the 8 of June to have my 7805 and 7905 replacement part.

    So first; i tried to change my multimeter mode : i set it a 2V or 200mV, but each time my multimeter screens show 1 or -1, and nothing more, and if i set at 2000V it write 003..

    My multimeter is dead ? i set something wrong ?

    Sorry for my newbie questions...i'm discovering the DIY universe.
  • i give you some photos of the board, maybe you’ll see something wrong !


  • Not that it has relevance with what your issue is but you put a bunch of your ic sockets in backwards.
  • As long as you put the ICs in the right orientation it's fine... but it's useful to have the IC socket shows the right example as to how the IC should be oriented.

    Yes, replacing the regulators is the only option I see ; but I find it really, really weird that both of them have failed at the same time, and to me the most likely explanation is a measurement problem!
  • ok, i will try to find another multimeter while i´m waiting for the parts !
    It´s a long way to listen what this little synth is doing.

  • ok, after this time i bought another multimeter, but i mesured the same result.

    i directly mesured the voltage on the plug of the adaptator, and i mesured 16.2V (red probe inside the 2.1mm plug and black outside)

    So it’s a power supply problem ?

  • The PSU voltage may rise quite a bit when unloaded, so you ideally need to measure its output when it’s plugged into the Shruthi-1. It should then be no higher than about 12-volts (and ideally 9-volts or less)


  • ok so i have to check the voltage just after the receptacle of the plug ?if yes, i already mesured the same voltage…

  • Unless you’ve missed out the wire link on the SMR-4 MkII circuit board next to the PSU input then that voltage is too high.


  • you mean the MS link ? (it´s the 4 PM). i put a link on the MS point so i don´t think it´s a problem.
    You can verify the link here : http://img694.imageshack.us/slideshow/webplayer.php?id=dscn1879z.jpg

    Bur maybe i don´t understand what you mean ;)

    Thx, Bye

  • Hi all, i give you some news !

    Finaly i changed the 7805 and 7905 !

    so my new mesurement :

    7805 :
    o : 5.03V

    - : 0V
    I : 14.6V

    7905 :
    o : -5.04V
    I : -14.2V
    + : 0V

    now i can mesured 5V somewhere but i don’t understand why i always find something close to 14.5V !

    i will continue to search if i don’t have a short somewhere but if you have soe idea ! just tell me !!!
    Have a good weekend !

    Bye :)

  • Yeah i did another test on the green red and blue pint on the IC and all looks like nice !!!! let’s continue !

  • Looks fine ; 14.5V is the input voltage of your power supply, fed into the regulators.

  • Oh, yeah !!!! all the synth seems to work, i hve to connect tthe lec and finish the box !

    i will give you some news !!!!!!!!! yesssssssss

    Thx all for your help !!!! Yihhhaaaaa

  • ok i’m on the test to adjust the Voct trimmer, but when i play a sound (actually there isn’t difference between octave), the sound is like a crushed signal (distortion) with a “poc” on the start ot he note.

    is it the normal sound ? cause i put a sin on the 3x osc of fruity and it sound a pure sound (like the sound you ear on the phone (bip bip)
    is it a hardware problem ?

    Thx and Bye

  • When you start the synth, with the “init” patch, does the resonance appear to work?

    Looks like there’s a problem on your build with the resonance circuit, which prevents the filter from self-oscillating.

  • no i don’t think, when i plug the shruti, the sound is really low i can’t ear nothing without a lot af gain.

    and the sound i ear now (different as my first try is like a little kick, the resonance pot don’t change nothing…. i really afraid…. i hope i hadn’t break something, or maybe the init patch…

  • Please post a big, sharp photo of the top and bottom of your filter board. You might have swapped resistors.

  • here are the photos :



    and all the photos of the top and bottom on the album :


    Thx Bye

  • Have you removed the chips just for taking the picture?

  • I can’t see anything wrong, but the photo is kind of overexposed and doesn’t show very well the colors of some resistors.

  • no it´s photo of the beggining, i will take better photo after the job !

  • plop; here is my new picture ! if you need ask resolution , ask me but i think it will be suffisant !


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  • I don’t see much wrong – maybe one of the 22k below the TL074 which looks like a 33k.

    Voltages to check:
    pin 7 of the TL074 – should go from 1.5V to 0V as you sweep cutoff from 0 to 127

    Audio signals to probe:
    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

  • to check the voltage, have i to use the Black probe on a ground point and the red on the point you said ?

  • yes that’s right

  • ok, i checked the resistor but it’s a 22k (i just invert his orientation)

    Voltages Check :

    Pin 7 : Nothing change on the voltage i always have 0 (but i’m not really sure my mpesuring is good)

    Audio signals :

    pin1 of IC1 – 0V
    pin1 of IC4 – 0V
    pin7 of IC4 – -3.57V
    pin7 of IC6 – 3.61V
    pin1 of IC6 – -3;58V
    pin8 of IC2 – 1;6V

    I rechecked all the solder point but nothing looks bad….

    maybe the IC4 is dead ?

  • Audio signals are not checked with a voltmeter, but with an oscilloscope or by connecting the point to an amplifier and listening…

    There’s definitely something wrong at pin 7 of the TL074. Are the two boards (filter and control) firmly connected?

  • yes, i mesured with the 2 board connected together (i used the solder point on the bottom of the card to mesure them.

    So i have to buy an occiloscope ?

    i don´t know if the one could be nice ?


    or this one ?

    Thanks, Bye

    ps how i can past a direct link on the page ? i can´t find the “balise”

  • €link text€:URL
    € signs mean “
    i can’t find the textile help box animore, sorry.

    link text

    you don’t need an oscilloscope, you can probe the points with an audio connector (tip to point, sleeve to ground) and to your stereo (low volume)

  • ok, so the synth must play some note from a sequencer until i mesure that point ?

    the result you need is what i listen ?

    ps : thanks for the BB code

  • you can hold a key on the shruthi down for longer than a second, that triggers a sound. make sure you have the preset patch selected, then the tone will be continuous.
    i think it was the osc key but you can look in the manual to be sure.
    if you hear something weird you can post some sound samples

  • You don’t need an oscilloscope for now. The very thing is to figure out why the cutoff doesn’t work.

    Which voltage do you read on the pin F> of the control board when you sweep cutoff from 0 to 127?

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