electro-music.com   Dedicated to experimental electro-acoustic
and electronic music
 
    Front Page  |  Articles  |  Radio
 |  Media  |  Forum  |  Wiki  |  Links  |  Store
Forum with support of Syndicator RSS
 FAQFAQ   CalendarCalendar   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups   LinksLinks
 RegisterRegister   ProfileProfile   Log in to check your private messagesLog in to check your private messages   Log inLog in  Chat RoomChat Room 
Live streaming at radio.electro-music.com

  host / artist show at your time
  Various Artists ~ 2014 Autumnal Equinox ~ live streaming radio ~
Please visit the chat
 Forum index » DIY Hardware and Software » YuSynth
LFO troubleshooting
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [11 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
Author Message
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Thu Nov 07, 2013 2:21 pm    Post subject: LFO troubleshooting Reply with quote  Mark this post and the followings unread

Hello everyone!
I've been watching this forum for a few months but now I decide to don't bother Yves by private mails Wink and join the group.
Some years ago I bought on ebay a LFO's pcb as a project. This year finally I've started to make a 3VCO yusynth system and I wanted to put the old LFO in. When I finished, wired and trimmed the LFO module I realize unfortunately that it doesn't sound like an LFO. The sound is drifting down. I mean - the pitch of rate is slowing down constantly (no cycles at all). The waveforms on scope are not ideal but looks quite good.
As I have the basic electronic skills I don't know how to fix it. I've read all topics about LFO's issues but find no solution.
Anyone of you have similiar problem? Any advice?
Thanks for answer.
Greg

I've attached photos of pcb (as you can see it's in poor state in some areas)


LFO_top.jpg
 Description:
 Filesize:  1.18 MB
 Viewed:  67 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

LFO_top.jpg



LFO_bottom.jpg
 Description:
 Filesize:  1.26 MB
 Viewed:  71 Time(s)
This image has been reduced to fit the page. Click on it to enlarge.

LFO_bottom.jpg


Back to top
View user's profile Send private message
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Sat Nov 09, 2013 12:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

I replace BC557B, LM741 & TLC555. No results.
That's all I can do Crying or Very sad
Back to top
View user's profile Send private message
ranioItaly



Joined: Feb 18, 2013
Posts: 13
Location: Italy

PostPosted: Wed Nov 27, 2013 8:45 am    Post subject: Reply with quote  Mark this post and the followings unread

hello,
could you attach some photos of oscilloscope wave shape?
so me and someone could try to help you.
bye
Back to top
View user's profile Send private message
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Thu Nov 28, 2013 10:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi!
Thanks for interest.
First of all, I realized that I wasn't clearly enough in my first post.
Obviously my issue is connected with too much high frequency. For some reason I couldn't dive too low by the rate pot and T1 trimmer.
In the meantime, I resoldered all solder points and replace c10uF 25V for 35V (I don't know is it relevant?). Then I decide to make a test, the same as Sebo made for Yves:

Quote:
OK check the voltages at the output of the 741 (pin 6). First adjust T1 to have 0V at its wiper pin. Then when cranking the frequency pot from min to max you should measure a voltage varying from 0V to -7V. Next measure the voltage at the base o Q1, there you should get something a voltage from 14,55V to 14,35V, that is a variation of 0,2V. If you have values significantly diffrent from these then the problem comes either from R1,R3,R5,R6,R7 or U4.


So I removed BS170 and measured 0V to -10.80V at pin 6 of the LM741 and 13,80V at base of Q1.
I replace R1,R3,R5,R6,R7 (by 1% in place of 5%).
That's all I did.
Now... Core signal is still unstable. When switch is on 1.0 position I have a frequency from 1000 to 8000 Hz and close to 8000Hz the signal is falling down about (50Hz/s), then about the middle scale of rate close to 3000Hz it is rising (10Hz/s)and when rate pot is close to minimum the signal is falling again.
In 0.1 switch position the frequency has the range from 20 do 1000 Hz - in the maximum the signal is rising up (10Hz/s), then close to 400Hz is drifting up and down and close to minimum - falling down again (5Hz/s).
So - the low frequency is appeared (that is a little progress) but when signal is starting to make a cycles (finally!) on a slow rate - it has maximum 1s long and soon it's falling down and became constant low (no cycles).
I tried to take a photos of the waves on my analog scope but with this unstable signal it is impossible - all photos are blurred.
Apropos: what about the waves? Now the waves are not good as before. 10V sawtooth looks like at added .jpg file.
The sine and triangle waves are far from their ideal, only the square/pulse looks good.
I hope this time I explain my issue better.
Thanks in advance for any help!
Greg


10V_sawtooth.jpg
 Description:
 Filesize:  7.83 KB
 Viewed:  1683 Time(s)

10V_sawtooth.jpg


Back to top
View user's profile Send private message
ranioItaly



Joined: Feb 18, 2013
Posts: 13
Location: Italy

PostPosted: Sat Nov 30, 2013 5:50 am    Post subject: Reply with quote  Mark this post and the followings unread

hello greg,
sorry if I do a stupid question, but Have you made a correct "Settings and trimming" as shown at the end of yusynth web page?
for me the frequencies that you say aren't right.
from web page:
" the frequency can be set with the RATE knob between 0.1Hz (10s repetition rate) and 100Hz (0.01s repetition rate) Switch on 1.0 position
or between 0.01Hz (100s rate) and 10 Hz switch on 0.1 position"

try to set properly T1 47K ohm trimmer for obtain the frequency as suggested by Yves.
bye
Back to top
View user's profile Send private message
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Sat Nov 30, 2013 11:33 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi!
I'm a beginner in electronic world, but I think the most important thing in this case is an unstable rate impulse. In fact this is the main problem. Right now it's impossible to set the frequencies properly. The range of frequencies from my previous post was an example of rate changes. If we can set the stable rate we will set the right frequencies easily. I made LFO#1 before and everything was ok so the triming process was simple & successful.
Anyway thank you for trying help. I'm appreciated.
Greg
Back to top
View user's profile Send private message
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Sun Dec 22, 2013 10:32 am    Post subject:  SOLVED! Reply with quote  Mark this post and the followings unread

Problem solved!
You never guess what was the reason of issue: partially-damaged wires.
I couldn't find the fault too long and I gave up - I made the new PCB, I bought new parts, I used the wires from the old PCB and... it wasn't working Mad .
I checked several times all connections, solder points, wires and all seemed to be ok. Then I accidentally bent the wires and the unit back to life for a one second Very Happy
So after replacing the wires, the LFO is in perfect working order.
I have to keep in memory Idea : always change old wires to new one.
Best regards,
Greg
Back to top
View user's profile Send private message
yusynth



Joined: Nov 24, 2005
Posts: 1224
Location: France

PostPosted: Sun Dec 22, 2013 12:11 pm    Post subject: Reply with quote  Mark this post and the followings unread

Glad you found yourself. This typically the type of problem that cannot be remotely sorted out. One must have hands on it to figure out where the trouble comes from.
_________________
Yves
Back to top
View user's profile Send private message Visit poster's website
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Sun Dec 22, 2013 4:52 pm    Post subject: Reply with quote  Mark this post and the followings unread

Hi Yves!
Yes, you are completely right.
But I'd like to have just a some electronic knowledge to know which part is responsible for which reaction. Then I would think to myself: "Hmm, to fix the issue I have to check R6 & R7". But, I'm still learning. Who knows, maybe 50 years from now, I can understand it Laughing
Anyway thanks again for sharing your stuff. It's a great module, as the rest of your system.
If you don't mind, I'd like to ask about another thing. The last issue of the first cabinet I made is a "saw animator grounding problem". It's a very strange thing. I have to plug a jack PARTIALLY into a mod_in input to start the internal control of animator/knobs react. If I plug a jack FULLY - it "switched" animator to external control/knobs not react. With nothing plugged into a mod_in input there is no effect - you can tweak the knobs left or right and the leds are blinking slow or fast as they should, but it not animate.
What you think, what might be a reason?
All my best,
Greg

By the way, santa Merry Christmas!
Back to top
View user's profile Send private message
yusynth



Joined: Nov 24, 2005
Posts: 1224
Location: France

PostPosted: Tue Dec 24, 2013 12:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Check that the jack socket is connected correctly. In particular that you did not exchange the tip lug and the switch lug of the socket.
_________________
Yves
Back to top
View user's profile Send private message Visit poster's website
gregcomposition



Joined: Oct 20, 2013
Posts: 10
Location: Poland

PostPosted: Tue Dec 24, 2013 4:33 pm    Post subject: Reply with quote  Mark this post and the followings unread

I was afraid you say that Smile
Yes, all seems like a simple incorrect connection, but I've checked it several times before and replaced twice with no results. I use a new one socket, but it doesn't help too. I guessed that it could be bad IC or something else. But if you said it should be a jack socket connection - I will try again to the bitter end. Thank you for your help.
On a side note, probably I could be wrong, but I think there is a typo in a saw animator's "The wiring diagram". Rate knob #2 has got misplaced connections according to the schematic.
Again Merry Christmas!
Greg
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic Moderators: Scott Stites
Page 1 of 1 [11 Posts]
View unread posts
View new posts in the last week
Mark the topic unread :: View previous topic :: View next topic
 Forum index » DIY Hardware and Software » YuSynth
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
e-m mkii

Please support our site. If you click through and buy from
our affiliate partners, we earn a small commission.


Forum with support of Syndicator RSS
Powered by phpBB © 2001, 2005 phpBB Group
Copyright © 2003 through 2009 by electro-music.com - Conditions Of Use