Frantone - Vibutron

KindaFuzzy · Post by **KindaFuzzy** » 13 Apr 2012, 00:36

Finally found one of these, and there's a lot less inside than I thought. Full gut shot gallery here: http://www.flickr.com/photos/35422385@N ... 803855603/

Chips are ICL8038ccpd, ua741cp, tlc2262cp, and a 2n7000 mosfet. Tracing will be done soon.

Bernardduur · Post by **Bernardduur** » 13 Apr 2012, 08:24

Cool!

Does the speed knob works the other way around as the one I had in a while ago (too short to make a schematic of even take pics)

Datasheet of the ICL8038; precision wave form generator, cool!

KindaFuzzy · Post by **KindaFuzzy** » 13 Apr 2012, 11:23

Yeah, it's backwards and has a huge range of speeds from super slow to crazy fast. The sine/triangle/square switch makes a big difference too, but gets lower in intensity as you go from square to sine, which is a little disappointing.

KindaFuzzy · Post by **KindaFuzzy** » 27 Apr 2012, 02:36

OK, here's what I've got, not verified yet since I don't have my 8038 chip yet, but should be good.

phibes · Post by **phibes** » 27 Apr 2012, 03:47

Simple design but very cool! I've read about the sine feed of the 8038 being weak before.

culturejam · Post by **culturejam** » 27 Apr 2012, 04:24

Sweet! Sounds kinda like the function generator chip that C'bread used on that tremolo thing that I can't pronounce.

By the way, has anybody done the relay switching on any of the Frantone boxes? I don't recall seeing it fully traced, but surely must have. I think I will search for that now.

mictester · Post by **mictester** » 27 Apr 2012, 05:27

phibes wrote:Simple design but very cool! I've read about the sine feed of the 8038 being weak before.

I'd buffer the output from the "Blend" pot - it would guarantee that anything you load it with wouldn't affect the operation of the FET.

The 8038 is quite expensive and draws a lot of current. You can get the same result with a quad op-amp and a couple of Schottky diodes - I use the conventional comparator and Miller Integrator triangular-wave oscillator (used in most phasers and flangers for the LFO), and then an op-amp and diode-based shaper for a reasonable sine-wave output, and you can get the square output from the output of the comparator.

The "spare" op-amp in the quad package can be used to drive the FET.

I'll try out an experimental version shortly - it's going to use two TL074s and a V-FET . The FET will be a BS170 as I don't stock the 2N7000, but the results should be similar, but with lower current consumption. I like the "blend" approach for depth!

KindaFuzzy · Post by **KindaFuzzy** » 27 Apr 2012, 11:29

phibes wrote:Simple design but very cool! I've read about the sine feed of the 8038 being weak before.

The sine option is the most disappointing as far as depth goes for sure.

KindaFuzzy · Post by **KindaFuzzy** » 02 Jun 2012, 03:23

So I ordered some 8038s from ebay, and they didn't work, so I ordered some more from another guy and it looks like they don't work either. I measured the voltages on the one in the pedal, and it's pretty obvious even without using my scope, that on the three function output pins the voltage is jumping up and down like it should, but nothing when I breadboard the chips I got. I tried the 'test circuit' from the datasheet too, and no dice.

Anyone got any ideas to test these differently, or have a few working chips they want to send me to finish verifying the schematic?

KindaFuzzy · Post by **KindaFuzzy** » 03 Jun 2012, 00:42

Got the audio part of the circuit verified, I fed it a square wave from a 555 and it worked fine. Just need to get some working 8038s and we're set.

IvIark · Post by **IvIark** » 03 Jun 2012, 02:04

I just got some of these too from JunFang-Electrons on eBay. Do you want me to send a couple?

KindaFuzzy · Post by **KindaFuzzy** » 03 Jun 2012, 02:51

You could, and I can send some parts in trade. Or you could just breadboard this sucker and confirm the schematic so I can dump this thing and get another pedal to reverse.

IvIark · Post by **IvIark** » 03 Jun 2012, 03:01

If I get chance to breadboard it over the bank holiday weekend I will do, but I'm not sure how much chance I'll get with the kids also off

If I don't get the opportunity I'll just send them out when the post office is open, you don't need to send anything in trade.

IvIark · Post by **IvIark** » 03 Jun 2012, 03:03

That sounded really bad, I do love my kids really!

Duckman · Post by **Duckman** » 03 Jun 2012, 09:10

ICL8038CCPD - Small Bear @ $9.95.-

KindaFuzzy · Post by **KindaFuzzy** » 03 Jun 2012, 13:23

Duckman wrote:ICL8038CCPD - Small Bear @ $9.95.-

Wow, how did I miss that?

Thanks Mark, and I feel your pain when the kid has to stay home all day too, makes you appreciate grandma's babysitting even more.

KindaFuzzy · Post by **KindaFuzzy** » 25 Sep 2012, 02:35

Few months later and I finally got an 8038 from small bear, plugged it in and nothing's working, uhh. Then I started fooling around with some wires, and bang the thing starts working. As long as I connected the 9v+ to pin 8 only and not pin 6 like you're supposed to, it works perfectly. Everything dies if I connect pin 6 to 9v, or remove the pin 8 to 9v, and things speed up if you connect 7 to 8 like on the data sheet. No idea why, maybe the current drain from the crappy battery I was using went below the working voltage of the chip once it was hooked up right, but I used the same battery in the working pedal and everything was OK. The 4 other chips I got from ebay all behaved the same.

So I guess this thing is verified, sort of. If anyone wants some cheap 8038s for their own project let me know, I don't even think I'm going to build one for myself, I like my ten cent trem better.

mrkaploca · Post by **mrkaploca** » 25 Sep 2012, 19:47

$380

For the clipping circuit (2N7000 substrate diode)?

Razvan S. · Post by **Razvan S.** » 26 Jan 2015, 14:13

Hi guys...I'm having a hard time with this, I built it twice, it does not work...I built it from scratch the second time...EXACTLY the same sympthoms as the first

I can hear the LFO ticking, the IC does something as far as ticking goes, the switches do something to the ticking, pots as well

The only problem is that the signal is dry and does not tremolo...but the guitar passes through

Some thoughts please? Thanks!

greenskull · Post by **greenskull** » 29 May 2017, 01:01

Razvan S. wrote:Hi guys...I'm having a hard time with this, I built it twice, it does not work...I built it from scratch the second time...EXACTLY the same sympthoms as the first

I can hear the LFO ticking, the IC does something as far as ticking goes, the switches do something to the ticking, pots as well

The only problem is that the signal is dry and does not tremolo...but the guitar passes through

Some thoughts please? Thanks!

Did you lift pin six of the function generator?
I recently built this from the Effects Layouts blog and needed to remove pin 6 of function generator from power to work (as noted in a previous post).
Also getting distortion on sine and triangle settings.... anybody else have this problem with this particular layout?
http://effectslayouts.blogspot.com/2017 ... utron.html

Frantone - Vibutron [traced]