e-licktronic Forum

Vincent stopped by tonight and answered my other thread but did not visit here, does he only check brand new threads?

Sorry for this mistake.

Check voltage on Pin14 of U1, you will find 5V.
Check Ground to pin 7 of U1
Check square wave on Pin2, 4, 6, 8, 10, 12. (post scope picture on this topic)

Check associated Schmitt trigger capacitor's and resistor's solder too. C1* to C6* and R40* to R45*.

Best regards,
e-licktronic

Hi Vincent,

I am replying to your last post too, I hope this is OK with Tom & Seven as we seem to be experiencing the same problem with our Cowbells.
I checked all the solder joints and went over them a second time.

U1 Pin voltages:
Pin 14 = 4.47v
Pin 7 = 0v

Here are the grabs you requested:
(I also included a reference grab of the scope analysing a Moog Square Wave, just to prove the scope is working OK).

U1 Pin 2


U1 Pin 4


U1 Pin 6


U1 Pin 8


U1 Pin 10


U1 Pin 12


Reference Moog Square Wave

There is a problem effectively.
Check Q9* base voltage.
Try to increase R60* to 6k8 to get 5V at U1 Pin14.
Check R53* value and solder (ground).
Did you try with an other Hex Schmitt trigger ?

Best regards,
e-licktronic

Many thanks for your reply.

R53* has continuity to ground and is a 1K resistor as per the build instructions.
Q9* base voltage is -14.20v (I put the positive probe from my Multimeter to the centre lead and the negative probe to ground). I hope that is the correct way to check.

I will get the 6.8k resistor in the next couple of days, and then try that too.

e-licktronic wrote:Did you try with an other Hex Schmitt trigger ?

Yes, although it was a generic version I got at a cheap price (just to try another chip), Texas Instruments CD40106BE to be precise. The result was exactly the same with this IC as with the original IC.

Dear Lfo2vco,

In waiting for the 6k8 resistor you can try to power the hex schmitt trig with an external 5v power supply.
+5v to Pin 14
ground to Pin 7.

DO NOT USE YOCTO POWER SUPPLY IN SAME TIME OF EXTERNAL POWER SUPPLY

Best regards,
e-licktronic

Hi e-licktronic,

e-licktronic wrote: Try to increase R60* to 6k8 to get 5V at U1 Pin14.

OK I replaced R60* with a 6k8 1% resistor, I now get 5.12v at U1 Pin 14.
However the scope output still looks the same as before and the Cowbell still sounds too low.

Any suggestions regarding what should I check next?

Dear Lfo2vco,

When you check U1 Pin with your oscilloscope, where do you connect ground of scope ?
On your measurement we can see that each Schmitt trigger are oscillated at the right frequency. The problem is the 50/50 cycle.
We are going to test each Schmitt trigger one by one.
First, de soldering R35 and scope check on U1 Pin6 with scope ground connect to U1 Pin7.
You should fine : 120Hz square wave F=1.2/(RC) F=1.2/560000*0.000000018 (R40*=560k, C1*=18n)
If not, change C1*, if Schmitt trigger still not oscillate change R40*.

Best regards,
e-licktronic

Hi Vincent,

Many, many thanks for your assistance.

It seems my mistake was not grounding the scope correctly! I did not think to use U1 Pin 7. So before unsoldering anything I retried the calibration correctly grounded as per your instruction and hey presto it all seems sorted now.

TM1* adjustment


TM2* adjustment


Sound sample
http://soundcloud.com/lfo2vco/yocto-cowbell

Cheers,
lfo2vco

@Tom Dee,
Did you solve your problem too ?*

Best regards,
e-licktronic

haha! solved Thanks for the assistance Vincent! Maybe put this in the building instructions for the newbies like myself...?