OCD 1.7

[Locrian99]

Hey guys,

I've been searching around trying to find a schem for the 1.7 OCD with no luck, plenty of the 1.4.  I've got a pcb for the 1.4, but have used the 1.7 and liked it.   Just trying to find what if any the component differences may be so I can socket those.  If anyone happens to know or knows where a 1.7 schem may be. 

[Rob Strand]

It's hard to keep up with the OCD versions.  There's a few sites going through the different versions but it's a long time
since I've looked at them.  I know I have many OCD schematics but they are archived and I don't know which version that stash ends in.

Here's short list I put together at some point.  It could contain errors.

V1.7 (incomplete, partial info)
- Early versions (upto 2013) have a V1.4 PCB and V1.7 written inside the case.
  Later versions (2014 and after) have V1.7 on the PCB
- Output volume pot seems to be 100kB (like V1.1, V1.2)
- D2 (germanium clipper) removed (like V1.1, V1.2). 
  (wire link on units with V1.4 PCB)
- One site mentioned larger PSU caps.
- Other changes - who knows!

So is it true the OCD V1.7 is a V1.2 with drive and tone pot changes?
(V1.2 might be muddled with V1.1 as my small "recent" stash has contradictory info.)

[Locrian99]

Hey thank you.  Interesting about the germanium diode.   I suppose I could just socket that probably not a bad idea for heat reasons anyways, and see if I like it with a jumper or without.   

From what I've seen at least in the 1.1-1.3 it's mostly changed in pots and tone stack cap changes.   

[Rob Strand]

Hey thank you.  Interesting about the germanium diode.   I suppose I could just socket that probably not a bad idea for heat reasons anyways, and see if I like it with a jumper or without.   

It wouldn't hurt to play with it.   Different people like different versions.

From what I've seen at least in the 1.1-1.3 it's mostly changed in pots and tone stack cap changes.   

Yes.

My (later) notes have this table but be warned it has not been thoroughly checked at all.

Layouts V1.1 to V1.4
https://tagboardeffects.blogspot.com/2012/02/fulltone-ocd-all-versions.html

Code Select Expand


        Volume Drive Tone Tone Cap Ge Diode Bias R
D2 R15?
V1 100kB 500kA 25kB? 100n - -
V2 500kB 500kA 25kB? 47n - -
V3 500kB 1MA 10kB 47n - 220k
V4 500kA 1MA 10kB 47n 1N34A 220k

V5 100kA 1MA 10kB ? - ?
V7 100kB 1MA 10kB ? - ?

25kB or 25kA? unclear as pot values not marked.


[Locrian99]

I'm assuming the 220k should be an n there?    I'm assuming volume pot changes just basically effect taper and output level.   Might be interesting to add a couple switches to change those values.   I'll have to play around with it. 

[Rob Strand]

I'm assuming the 220k should be an n there?    I'm assuming volume pot changes just basically effect taper and output level.   Might be interesting to add a couple switches to change those values.   I'll have to play around with it.

I'm not sure.  That's one of the things that needs checking. (I've got no recollection if it was there or not in my old stash either.)

There's some Joyo OCD clone schematics on the web which have the resistor in that area of the circuit positioned differently to the OCD schematic (which calls it R15).

It's not going to make a lot of difference.

So yeah, unfortunately a few loose ends.

[Locrian99]

More info than I had before.   I was already contemplating using a switch for that cap, I didn't realize they took out the germanium diode.   1.4 much like 2.0 seems to garner some strong opinions from folks.   I can't help but wonder if 1.7 was kind of just Fulltone deciding well we tried that, let's go back to the previous wag and call it a new version.

[Rob Strand]

I can't help but wonder if 1.7 was kind of just Fulltone deciding well we tried that, let's go back to the previous wag and call it a new version.

I'm not sure how he works.   He could tinker in the comfort of his own home and release what he thinks is best at the time, or, he could get market feedback and bend things towards what the market wants.

[Locrian99]

I found this....

https://www.tonestart.com/fulltone-ocd-versions/

Of course I have to wonder on the accuracy.   I'm not expert but I wouldn't think just changing the volume pot would change the tone.  And doesn't jive with the tag board info.  Anyways. 

[Rob Strand]

I found this....

https://www.tonestart.com/fulltone-ocd-versions/

Of course I have to wonder on the accuracy.   I'm not expert but I wouldn't think just changing the volume pot would change the tone.  And doesn't jive with the tag board info.  Anyways.

Yes, that was one of the sites I had.    For accuracy you can only read over stuff and look at a few board pics.  The part values aren't easy to see in the pics.   The guys that buy all the pedal versions and decipher them generally have a good view of the landscape.

FWIW, the pot change to 100k slightly changes the way the tone control works.   It pushes up the frequencies in post-effect "bass" equalization ; part of evening out the response.   The signal loss is slightly more as well - no big deal.

Here's a few other links saved in my files,

https://www.tonestart.com/fulltone-ocd-versions/

https://www.albertodessi.it/guide-e-consigli/31-fulltone-ocd-versioni/356-fulltone-ocd-all-the-7-versions

https://www.thegearpage.net/board/index.php?threads/fulltone-ocd-version-1-5-difference-from-1-4-with-photos.2005578/

https://www.deluxeguitars.com.au/products/fulltone-ocd-v2

https://www.efmaniac.com/fulltone-ocd-ge-review/

There was another forum thread on a guitar/pedal forum.   There was a link that no longer existed and I had to go to web archive.   Unfortunately I don't have all the links, I kind of start just for interest not gathering links then if it gets complicated I start saving references.   I didn't keep any links for schematics or board pics.

Beyond that was the joyo and the Danelectro "clones";  you need to know when the pedal was made to get an idea which version was cloned.    They aren't 100% clones but you can see how the circuit gets messed with.

[Locrian99]

Thanks again.  Lots to play around with there, I think this gives me an idea of things to try may just have to breadboard it rather than socketing on the pcb.   Would be curious to try two germanium diodes rather than just the one as mentioned for the ge+ version. 

[Rob Strand]

Thanks again.  Lots to play around with there, I think this gives me an idea of things to try may just have to breadboard it rather than socketing on the pcb.   Would be curious to try two germanium diodes rather than just the one as mentioned for the ge+ version.

You might find some nuggets I've missed.

If you use two germanium alone the output level will drop so the sound level won't be the same when you switch between them.  If you used four germaniums, two in series each direction then the level will be closer to the original.    I'm sure I've seen a video or two where Wampler pedals recommends this as well.

I've got a schematic with blue markups but I don't know if the part designators on the schematic actually match the PCB.  I also don't know if designators for the same part position change across different versions of the OCD.    So when follow the PCB and the schematic you need to be aware you might be looking at different parts!  Not good if you are modding stuff on a real unit.  (If you have a real unit then at least you can check the surrounding circuit matches the schematic.)

[Locrian99]

Again thanks for the info you got me doing more looking into clipping diodes and I found this great bit of info.  https://www.diystompboxes.com/pedals/diodes.html Going to have myself overwhelmed with info even before I start breadboarding this thing.   

[PRR]

I found this....

https://www.tonestart.com/fulltone-ocd-versions/ ..... I wouldn't think just changing the volume pot would change the tone.  ...

If you read the words of Fuller on that page, ANY change merited a new number, even if not "sound". (Just good technical management.) And he himself doubts any real sonic change, though he knows that internet users will argue all different things.

[Locrian99]

Well my ears decided I went with the straight values from the pcb which seem to be the same as 1.2 and 1.3 other than pot changes.   I'm up in the air if I want to just do the jumper or make it a switch for the diode.    I prefer no diode. 

[Supashane]

Concerning the earlier questions of the 1.7 values. The 1.7 has a few value changes in the gain section, as well as a resistor coming off the tone control to ground that is not present in the earlier versions. I recently traced my personal 1.7 to create some clone PCBs, the schematics below have been verified against two separate v1.7 OCDs, a friend's unit from 2013 and mine from 2015. Figured since I was writing build docs for them, might as well share my findings with the community at the same time, being as there isn't much info on the 1.7.

Here is the schematic from the initial tracing, including the noiseless switching circuit. (it's a bit messy due to drawing out the schem from following the traces exactly)
https://a73e2e3e-6c61-45ff-abff-ee778a4dcb5f.usrfiles.com/ugd/a73e2e_da9e861d7f774a86990fc3bef66ce73f.pdf

Here is a cleaned up version of that one that has been modified to accept a few part substitutions if needed, for compatibility with popular true bypass methods and redrawn to follow a bit neater schematic layout.
https://a73e2e3e-6c61-45ff-abff-ee778a4dcb5f.usrfiles.com/ugd/a73e2e_3c480df2dc7f4a129735257e26b02f1c.pdf

I may convert the PDFs to jpg in a later post for people that would rather that. Enjoy!

[Locrian99]

Funny timing friend of mine who does a lot of buying/selling just messaged me a few hours ago asking me if I wanted to look at a 1.7 he just picked up.   Thank you for this, saved me some time. 

Just did a quick comparison with the schem I have for 1.4, other than the diode (which I ended up making switchable in my build, but the difference is subtle) the only difference is r11 and a 500k volume pot vs. 100k oh and the output cap 10u vs 1u.   Theres a couple differences in the power section, that I doubt effect tone at all as well. 

[Supashane]

No problem! I think C12 and R20 may have had different values in the 1.4 as well, from schems I've seen online, so I can't verify. I can only verify the 1.7 lol. But yeah, there were some differences in the power section i believe from what I've seen in gut shots, having to do with the filtering section from what i could tell. Also, using both D1 and D3 together seem a bit redundant, maybe there is a reason beyond my current knowledge as to why they are both there.

[Locrian99]

Interesting, the coda effects schematic for the 1.4 matches the 68nf and 2k2 and I just did a quick glance at the vero layouts over on tagboard effects and they all have those values as well.   As was stated before in this thread lots of varying info out there I guess. 

[Rob Strand]

Concerning the earlier questions of the 1.7 values. The 1.7 has a few value changes in the gain section, as well as a resistor coming off the tone control to ground that is not present in the earlier versions.

Good work, thanks.  So it's a lot like V1.4.