SMR4 : no cutt off no resonance

I have a problem with the filter SMR4
I have sounds and the shruthi works but I do not have a cut-off or resonance (that a pity for a filter).
Please help me
Is that you have a track ? or a solution?
In the diagrams all IC is related to the cut off , what is IC that controls the parameters of the filter ?

Post a picture of your boards with good resolution + check the test points shown in the last section of the SMR4 mkII build instructions.

when i check points i Have whith :
ground and red point : 5.02V
ground and green point : 0.64 V

Perhaps i find my problem , is it come to a IC5 regulator ?
Do you know how much voltage i need for IC5 7905 ?

Which voltage do you have on each pin of the two regulators? (I’m expecting 6 voltage readings).


Regulator 7905
AB : 0.13 V
BC : 0.50 V
AC : 0.64 V

Regulator 7805
AB : 5 V
BC : 14 V
AC : 9 V

Hello pichenettes,
I understand I only need to change the 7905 regulator is not it ?

The problem is probably with the LT1054 (which is likely to have been destroyed), and with your power supply to start with since it delivers 14V rather than the expected 9V.


  • Which power supply do you use?
  • Why didn’t you do the power supply tests earlier? (in the assembly instructions, you need to do the power supply test before soldering the rest of the parts).

I haven’t got excuses, I did not do the tests.
At first I already grilled lt1054 by changing with the TL072.

I also use can be too much power.
I will change the Power Supply and Lt1054 and try again tonight

I do not understand why there was another TL072 instead of TL1054…(for the second time, sometimes i’m really a stupid boy)
Now i’m happy the problem is over, I changed the good IC and everything works well

Thank you very much Pichenettes

Be happy that the little chips withstood well the abuse you put them through!