Fulltone - OCD

95strat · Post by **95strat** » 30 Dec 2009, 20:55

I think where I'm getting confused is the schematic and layout numbers don't match. C10 on MarkM's board is C9 on the schematic, and C10 on the schematic is C9 on MarkM's board. Correct me if I'm wrong.

Anyway, I have a 10n cap in C10 position (schematic), but it looks like I have C9 (schematic) incorrect. It should be a 10uF Electrolytic. Maybe that's what you were saying all along.

Post by **modman** » 30 Dec 2009, 21:06

Never ever build from a layout that isn't accompanied by a (correct) schematic. Start from a verified schematic then put a layout you want to use next to it. It wouldn't be the first MarkM layout that takes some liberties it doesn't mention...

95strat · Post by **95strat** » 30 Dec 2009, 22:20

modman wrote:Never ever build from a layout that isn't accompanied by a (correct) schematic. Start from a verified schematic then put a layout you want to use next to it. It wouldn't be the first MarkM layout that takes some liberties it doesn't mention...

Good advice! I had made the PCB a long time ago and thought I would just finish the build. Lesson learned!

Seems a few people around here have had success with the same board. They probably read the schematic though.

newly · Post by **newly** » 31 Dec 2009, 02:56

IIRC...Mark's layout has some different in TONE circuitry.

95strat · Post by **95strat** » 31 Dec 2009, 19:12

Finally got this thing working correctly. I was wiring the pots incorrectly. Amazing how close to the real deal this thing sounds. Thanks for the help guys. Here's a couple of pics.
Guts:

Box:

useme2305 · Post by **useme2305** » 31 Dec 2009, 19:41

i built the ocd based on the vero layout.
http://i50.tinypic.com/334i69f.png

all i'm getting is a fuzz like sound.
when the drive pot is all the way down it's kind of gated and really fuzzy when i hit the strings.
almost like my woolly mammoth with the pinch control all the way down to have that gated starving effect.

i tried different 2N7000s as i ordered a bunch. i also tried turned them around 180 degrees. still the same.
the pedal has almost zero dynamic range.

here's a pic of component side of the vero board:
http://i46.tinypic.com/23igscm.jpg

caspercody · Post by **caspercody** » 31 Dec 2009, 19:49

You could take the 2N7000's completely out, and it should still work. Might want to build an audio probe, and work your way thru the circuit. When I build a pedal that is not working right, this is what I do.

In fact when I did build this pedal I did have a issue of it fizzing out. I replaced a bad electro cap, and now it works. You can also remove the diode, and try it without.

madbean · Post by **madbean** » 31 Dec 2009, 20:26

Without the diode you will still get pretty nice clipping. The diode itself kinda softens the transition to clipping, but it also adds some grittiness I found. I've experimented quite a bit with 2n7000 tied to Vb in other circuits, and I always preferred it without the 1n34a.

Actually, looking at Mark's layout the transistors are wrong. Drain and Gate should be connected, not Gate and Source. Flip them around....Source should be the free pin.

madbean · Post by **madbean** » 31 Dec 2009, 20:37

Also, if you are using the GE diode, the cathode (band) should point towards the source pin. You can use a diode on each tranny, or just one, or none.

culturejam · Post by **culturejam** » 31 Dec 2009, 20:38

madbean wrote:Without the diode you will still get pretty nice clipping. The diode itself kinda softens the transition to clipping, but it also adds some grittiness I found. I've experimented quite a bit with 2n7000 tied to Vb in other circuits, and I always preferred it without the 1n34a.

I actually like the MosFET-only clipping sound as well.

95strat · Post by **95strat** » 02 Jan 2010, 18:24

madbean wrote:Actually, looking at Mark's layout the transistors are wrong. Drain and Gate should be connected, not Gate and Source. Flip them around....Source should be the free pin.

Are you serious? I didn't even catch that. I'll have to take another look at the schematic and try flipping them. Thanks for the info. I'm never building a layout without a match schematic again!

sevinisthenumber · Post by **sevinisthenumber** » 27 Jan 2010, 08:08

please be gentle....

I cant find how to make a version 2?
ANyone lead me the right way/layout/etc...
Thanks

ianZeds · Post by **ianZeds** » 27 Jan 2010, 14:22

i think it is just one cap and different pot values

http://www.fulltone.com/ocd_mods.html

kungpow · Post by **kungpow** » 04 Feb 2010, 07:20

Hey good people,

So I am putting this guy together based on this:

I don't see an output from the board? Am I blind? Didn't even notice till I was done populating the board and wiring up

Would it be Vol lug 2, since that has nothing attached to it? I wired it that way, cuz i didn't know what else to do

I'm not getting an effect signal as it is now

And by reading this thread, I know I wired my SPDT wrong

Thanks for any help!

Greg · Post by **Greg** » 04 Feb 2010, 07:41

kungpow wrote:Hey good people,

So I am putting this guy together based on this:

I don't see an output from the board? Am I blind? Didn't even notice till I was done populating the board and wiring up

Would it be Vol lug 2, since that has nothing attached to it? I wired it that way, cuz i didn't know what else to do

I'm not getting an effect signal as it is now And by reading this thread, I know I wired my SPDT wrong

Thanks for any help!

Yes, the output is from the centre lug of the Volume pot as per schematic.

useme2305 · Post by **useme2305** » 04 Feb 2010, 09:17

kungpow, since you obviously didn't even take a look at the attached wiring scheme:
don't forget to ground lug one of the vol and tone pots.

Greg · Post by **Greg** » 04 Feb 2010, 10:16

useme2305 wrote:kungpow, since you obviously didn't even take a look at the attached wiring scheme:
don't forget to ground lug one of the vol and tone pots.

That's marked on the layout..

Dr Tony Balls · Post by **Dr Tony Balls** » 04 Feb 2010, 14:19

I built from that layout and can confirm it.

B_of_H · Post by **B_of_H** » 04 Feb 2010, 16:53

I've been gigging with a build from the above layout for close to a year now. I did play around with the values of c10 and c11. I'm not sure what I ended up with but the pedal is a lot brighter than it was with the stock values. I use it with the tone at about 11:00 now instead of 2:00 or higher when I first built it stock.

kungpow · Post by **kungpow** » 04 Feb 2010, 19:20

Yay!

Thanks for the responses. Got it to work; sounds good, not quite as much gain as I would've expected when dimed. A few questions remain, however:

1)

Greg_G wrote:
useme2305 wrote:don't forget to ground lug one of the vol and tone pots.

I wired them together. Is that grounded?

2) I know the HP/LP switch is a high/low pass filter. Seems when I put it in HP, I get a noticeable Vol boost. As I interpret the layout, I have lug 3 of Vol pot to lug 1 of S1, and then the board's "S1" to lug 2 of my SPDT. Then I put a small jumper btwn lugs 2 & 3 of that. Is this normal/others experience? Am I wiring this right?

3) Lug 3 of Drive pot is empty. Should it be grounded, or o/w attached to something?

Thanks!

Fulltone - OCD [traced]