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 Forum index » DIY Hardware and Software » YuSynth
LFO Problems
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yusynth



Joined: Nov 24, 2005
Posts: 1233
Location: France

PostPosted: Fri Feb 27, 2009 9:34 am    Post subject: Reply with quote  Mark this post and the followings unread

Check that you soldered the jumper that connects pin1 of the 7555 to the ground.
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joshco



Joined: Nov 14, 2008
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Location: germany

PostPosted: Fri Feb 27, 2009 10:26 am    Post subject: Reply with quote  Mark this post and the followings unread

all jumpers are soldered and i have tried diffrent 7555 chips...
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yusynth



Joined: Nov 24, 2005
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PostPosted: Fri Feb 27, 2009 12:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

Have you correctly connected the range switch (as shown on the wiring diagram) ? Make sure that the wire the closest to the 7555 goes to the middle lug of the switch and the two other wires to the extreme lugs (upper and lower) of the switch.
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joshco



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PostPosted: Sat Feb 28, 2009 5:15 am    Post subject: Reply with quote  Mark this post and the followings unread

yusynth wrote:
Have you correctly connected the range switch (as shown on the wiring diagram) ? Make sure that the wire the closest to the 7555 goes to the middle lug of the switch and the two other wires to the extreme lugs (upper and lower) of the switch.

Yes, the switch is connected like in the wiring diagramm. The Pots and rotary switches, too.Sebo had some difficulties with the switch, but they are conected to the caps and trimmers like in the schematic...
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yusynth



Joined: Nov 24, 2005
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PostPosted: Sat Feb 28, 2009 5:20 am    Post subject: Reply with quote  Mark this post and the followings unread

OK to this point there nothing much that can be done without an oscilliscope.
Can you use the sondboard of your PC and an oscilloscope software to check what's happening at pin 5 and 7 of U2b.

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joshco



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PostPosted: Sat Feb 28, 2009 6:31 am    Post subject: Reply with quote  Mark this post and the followings unread

here is the graph of pin5 (upper) and pin 7 (lower), looks rather good...

Posted Image, might have been reduced in size. Click Image to view fullscreen.

Posted Image, might have been reduced in size. Click Image to view fullscreen.

havent adjusted the time and amplitude
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yusynth



Joined: Nov 24, 2005
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PostPosted: Sat Feb 28, 2009 6:37 am    Post subject: Reply with quote  Mark this post and the followings unread

No it does not look good, I don't now what is the time base of the graphs but to me it looks like 50Hz hum.
You should have a clean rising sawtooth.
Try changing the BC557B.

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joshco



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PostPosted: Sat Feb 28, 2009 6:45 am    Post subject: Reply with quote  Mark this post and the followings unread

i understand, i´ll have to go to the shop for a bc557, ill reply when i have some.
by now a big thanks for your support Very Happy
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yusynth



Joined: Nov 24, 2005
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PostPosted: Sat Feb 28, 2009 7:13 am    Post subject: Reply with quote  Mark this post and the followings unread

Make sure it's a BC557C the C at the end does matter here !

[EDIT] Yes, my mistake : READ BC557B B DOES MATTER HERE[/EDIT]

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Last edited by yusynth on Sun Mar 01, 2009 3:24 am; edited 1 time in total
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Sebo



Joined: Apr 27, 2007
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PostPosted: Sat Feb 28, 2009 1:57 pm    Post subject: Reply with quote  Mark this post and the followings unread

yusynth wrote:
Make sure it's a BC557C the C at the end does matter here !

Sorry, shouldn't be a BC557B?

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My Music:
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www.myspace.com/cosaquitosenglobo
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yusynth



Joined: Nov 24, 2005
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PostPosted: Sun Mar 01, 2009 3:24 am    Post subject: Reply with quote  Mark this post and the followings unread

Sebo wrote:
yusynth wrote:
Make sure it's a BC557C the C at the end does matter here !

Sorry, shouldn't be a BC557B?

Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed Embarassed
Yes, my mistake : READ BC557B B DOES MATTER HERE

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joshco



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PostPosted: Mon Mar 02, 2009 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

yes, I have taken the bc557b as described in the BOM, however, it still does not work. Again, a new 7555 is also installed.
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joshco



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PostPosted: Tue Mar 03, 2009 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

well, as i checked my resistors box i recognized that there were some wrong values in the box, next thing is to check the correct values at the pcb, maybe there is something wrong...
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yusynth



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PostPosted: Tue Mar 03, 2009 12:16 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi

Yes a thorough check of the components and solder pads may be the solution as it seems that everything is correct upto Q1

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Thalassa



Joined: Jan 27, 2006
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PostPosted: Wed Mar 04, 2009 3:53 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hello Yves , I have a question also about the LFO.

There's a problem with the number of capacitors. According to the "list of materials" , there're only 2 100nF capacitors ( in the schematic also ) , but in the component layout there're 4 of this capacitors.

And also in the version 1 , C6 is supposed to be off board , but on the wiring diagram there's no capacitor and also on the schematic there isn't C6 capacitor.

Thanks

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yusynth



Joined: Nov 24, 2005
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PostPosted: Wed Mar 04, 2009 4:22 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thalassa wrote:
Hello Yves , I have a question also about the LFO.

There's a problem with the number of capacitors. According to the "list of materials" , there're only 2 100nF capacitors ( in the schematic also ) , but in the component layout there're 4 of this capacitors.

These are filter caps connected close the power supply pins of the ICs. Just add them as shown on the component layout diagram.

Thalassa wrote:
And also in the version 1 , C6 is supposed to be off board , but on the wiring diagram there's no capacitor and also on the schematic there isn't C6 capacitor.

For LFO1, C6 is not required since there is no SYNC circuit in this version, I will correct these minor typos.

Thanks for reporting these.

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Thalassa



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PostPosted: Wed Mar 04, 2009 4:43 pm    Post subject: Reply with quote  Mark this post and the followings unread

ok Smile , Thanks Yves
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yusynth



Joined: Nov 24, 2005
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PostPosted: Thu Mar 05, 2009 12:53 am    Post subject: Reply with quote  Mark this post and the followings unread

I made the update on my site for C6 and other filtering caps...
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Thalassa



Joined: Jan 27, 2006
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PostPosted: Tue Apr 14, 2009 9:04 am    Post subject: Reply with quote  Mark this post and the followings unread

Hello Yves , I just finish to built the LFO version 2. Everything works fine after calibration Smile but I have a problem with the sync input.

When I connect gate / trigger signal to de sync input I get a pulse that instead a cycle restart. The length of the pulse is dppendent of the flo frequency.

I've made a few tests before post this, I've changed the BS170 for a BC547 , I've changed the BS170 for another BS170.

I've changed the C6 capacitor for new one.

All of this tries didn't solve the problem.

I've attached a picture with the output of the lfo where you can see the pulse when the sync signal is received.

Also I've attached an audio file the LFO is modulating the filter frequency , and as you can see the pulse length changes when LFO frequency changes.
( I've updated the audio attachment, previously was empty Embarassed )


lfo_sync.jpg
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lfo_sync.jpg



lfo_sync.wav
 Description:
this one is not empty :)

Download
 Filename:  lfo_sync.wav
 Filesize:  6.52 MB
 Downloaded:  196 Time(s)


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Minimalist



Joined: Nov 21, 2008
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Location: NZ

PostPosted: Thu May 28, 2009 6:37 am    Post subject: LFO sine waveform like a triangle wave Reply with quote  Mark this post and the followings unread

Hi Yves

Thanks for your generous sharing, I've built one of your LFO version 2, it all works well except the sine waveform isn't right. It is adjustable but is comming out like a pure triangle wave with no rounding, all the other waveforms seem right.

Any suggestions where to look?

thanks Marcus
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Thalassa



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PostPosted: Thu May 28, 2009 6:46 am    Post subject: Reply with quote  Mark this post and the followings unread

Probably you already did it but ... check T3 ( the trimmer near of the power connector ) , with this trimmer you adjust the shape of the sine wave ( from triangle to sine wave )
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Minimalist



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PostPosted: Thu May 28, 2009 12:09 pm    Post subject: LFO Sine wave shape problem Reply with quote  Mark this post and the followings unread

thanks Thalassa, yes I've tried varying the sine wave shape trimmer I'm getting the following variations , ie the top or bottom half of a sine wave but not the whole wave, any suggestions? I'm getting perfect triangle and saw waves.

Thanks Again


sine 2.jpg
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sine 2.jpg



sine 1.jpg
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sine 3.jpg
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sine 3.jpg


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yusynth



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PostPosted: Fri May 29, 2009 5:20 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi seeing the oscillogram it is clear that the triangle wave has not the right amplitude. Check that the level of the triangle output is at 8Vpp (-4V/+4V).
If so then check thoroughly the value of the following components :
R26=150K, R27=22K

If the amplitude of the triangle is <<8Vpp then check R23=200K1%,

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Minimalist



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PostPosted: Wed Jun 03, 2009 12:40 am    Post subject: Reply with quote  Mark this post and the followings unread

Thanks Yves
wow you really know your stuff, the triangle was <<8Vpp so I checked all the recommended resistors, they were all correct so I just increased R23 to 300K which brought up the triangle to just over 8vpp which meant the sine wave now is good, thanks again for your patience with beginners questions.

Marcus
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yusynth



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PostPosted: Wed Jun 03, 2009 1:23 am    Post subject: Reply with quote  Mark this post and the followings unread

Minimalist wrote:
Thanks Yves
wow you really know your stuff, the triangle was <<8Vpp so I checked all the recommended resistors, they were all correct so I just increased R23 to 300K which brought up the triangle to just over 8vpp which meant the sine wave now is good, thanks again for your patience with beginners questions.

Marcus

Great, however if the triangle was <<8pp then this mean that something was wrong with the sawtooth which must be at least 8Vpp. In the LFO, the core is a sawtooth wave anad all the other waveshapes are derived from it. This means that if the sawtooth has not the right amplitude then all the values of the wave-shaper resistors has to be adjusted.
Just as a matter of being sure and understand why you had to increase R23 to 300K can you check the values of R9,R1,R19,R20 and R21. ? Wink

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