Note: Red lines are jumpers
Wednesday, May 3, 2017
Frantone Vibutron
Here's another one of my Eagle creations. The Vibutron is a great sounding tremolo from Frantone that uses a ICL8038 to produce the LFO. Originals use a rotary switch for selecting the waveform, but as lvlark pointed out on the Tagboard Effects blog, a on/on/on DPDT switch can be used instead (check out his layout for switch wiring). For you perf builders, this might be a bit difficult to translate to perf (especially with 3 traces under the 8038), but I'm sure one of you out there will make it work. :D This layout has also been uploaded to OshPark if you want a fabricated board–click the OshPark tab above.
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Are you putting this up on OSH? I dont see it listed under the tab you provided. nor does it appear if you search for Vibutron
ReplyDeleteSorry! Forgot to share it. It's there now.
DeleteYou are truly AWESOME!
ReplyDeleteAwesome! Would you consider putting your first few Eagle boards up on OSH?
ReplyDeleteWould it be possible to link the schematic for debugging, because i get only the dry Signal. I used the oshpark pcbs
ReplyDeletehttp://www.freestompboxes.org/viewtopic.php?f=7&t=17029&p=204378&hilit=+Vibutron#p204378
DeleteFound it.
Hello! Yesterday I collected it and it does not work, there is a clear sound, the functional works, but nothing changes, I spent the whole night on this problem (
ReplyDeletehttps://www.dropbox.com/s/j5i8net7mmvf7hi/IMG_20170620_105749.jpg?dl=0
So i finished the oshpark pcb and ran in some issues. I had to lift pin 6 from icl8038 to get the lfo running, like mentioned in the fsb Thread and the 2n7000 won't switch, because because of to Low voltage. No idea if i have a faulty batch of transistors. But swaping the 100k trimmer for a 500k did it. So now it's working. Maybe the Layout could be altered, for easier lifting of pin 6?i know it's only an issue few people have, at least in the fsb Thread.
ReplyDeleteНе работает
ReplyDeleteHi, Managed to build this (oshpark boards). had to lift pin 6 like Samuel. works great, sounds good, I've added the fast switch mod from MArks forum. Very good Tremolo.
ReplyDeletehow can i wire it using a rotary switch? tnx..
ReplyDeleteThis is heroic. Any chance you'll ever do a layout of the Cream Puff?
ReplyDeletevery low quality on the picture, cant see the values.
ReplyDeleteif i zoom it gets too blurry :(
Right click on the image, select "Open link in new tab"
Deleteok I see, thx
Deletethat's a bit better.
maybe it's not the best color combination to use in first place? ;)
After 4 attempts of PCB etching from the transfer library I must say that the traces on this one are a bit too thin - I always ended up with a couple of opened circuit traces each time. Shame, as this is a cool example of using the 8038.
ReplyDeleteHello...
ReplyDeleteAfter looking around online for a tremolo pedal to build, I decided to check this one out.
Then after listening to it, I decided that this one would be a great candidate UNTIL i read everyone's posts on it.
I see that everyone was having the same problem with the waveform generator not working, so being an Electronics Engineer, I decided to find out "what was wrong" with it and because more than one person had said that they did the same thing to get it to work.
SO....
Here's the problems I have found with this layout, and "alterations" that everyone seems to be having / had with this after building it.
#1 - Pin 6 absolutely has to be connected for the ICL8038 to operate.
#2 - Pins 7 & 8 should be directly connected together. The PCB Layout above has THIS ERROR as Pins 6 & 8 are tied to the Vcc+ rail.
If you look at the ICL8038 Datasheet, (Found here - http://www.mit.edu/~6.331/icl8038data.pdf), you will notice that this frequency generator part of Fran's circuit is taken directly from it. (Page 5 Figures 3A and 3B)
Figure 3A shows 82K resistor to Ground - Fran used a 91K (Pin 12)
Figure 3A shows "C" to Ground - Fran used 220nF (0.22uF) capacitor - I used 0.1uF (Pin 10)
Figure 3B shows the "Speed / Frequency" Potentiometer (Pins 4, 5 and 6)
Figure 3B RA and RB resistors Fran picked 390 Ohm
Figure 3B 1k ohm pot was changed to 100K with a 7.5K ohm resistor tied to lug 1 of the potentiometer and the other end of the resistor tied to Vcc+
Figure 3B RL was put in as a 10K ohm resistor for the load.
Now if you scroll down to page 7, Figure 6 of the datasheet for the ICL8038, You will notice the use of the UA741 Opamp as a buffer stage.
Fran uses a rotary switch from pins 2 (SW1), 3 (SW2), and 9 (SW6) with the center (SW5) connected to pin 2 thru a 10K ohm resistor for driving the buffer stage.
So I noticed that both this layout and OHS Parks boards have this same design flaw. OSH Park tied pin 8 to the Vcc+ rail on the top layer of of the board and left pin 7 unconnected. This is why everyone is having problems with this build.
ReplyDeleteIf you have the above layout etched out, just cut the trace going from pin 6 to pin 8 and put a jumper wire from pin 7 to pin 8 then cut the trace from pin 8 to the 10K ohm resistor and put a jumper wire from the 10K ohm to Pin 6
If you have OSH Parks board, it will be a bit easier to fix. you will have to unsolder the IC (ICL8038) cut the trace all the way around pin 8 on the top layer of the board then put the ICL8038 back in and then put a jumper from pin 7 to pin 8
If you have done this correctly the pedal should work like it should.
Hello Eddie,
DeleteAccording to this link pin 7 and 8 doesn't appear to be connected.
Also 6 and 8 look connected to me.
https://www.flickr.com/photos/35422385@N07/sets/72157629803855603/with/6926185206/
any chances you have the schematic? I'm specially interested in the LFO part
ReplyDelete