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Re: Fulltone - OCD

PostPosted: 06 Jan 2012, 14:10
by jymaze
On first intention, just put a jumper instead of the 18k resistor in the first opamp feedback loop (the one in series with the 1Meg pot). The minimum gain will then be merely a slight boost.

Re: Fulltone - OCD

PostPosted: 06 Jan 2012, 19:16
by geiristudio
jymaze wrote:On first intention, just put a jumper instead of the 18k resistor in the first opamp feedback loop (the one in series with the 1Meg pot). The minimum gain will then be merely a slight boost.


Alright, I'm gonna try that, thanks!

Re: Fulltone - OCD

PostPosted: 26 Jan 2012, 23:24
by ebuprofen
hey guys, what would be a good value for pot instead of 22k resistor in HP mode? so I could adjust the amount of boost? 500kB?

Re: Fulltone - OCD

PostPosted: 22 May 2012, 07:20
by yongki
Image

Re: Fulltone - OCD

PostPosted: 27 Sep 2012, 06:27
by Branimir
Trying to find info...

What type of capacitors are use in OCD V4?
Electrolytics are tantalum? All of them? What about the others?

Re: Fulltone - OCD

PostPosted: 27 Sep 2012, 15:49
by batteryacidtea
Theres just one capacitor (one of the 10uF's) is Tantalum, the others are eletrolytics. The tantalum cap is usualy highlighted in the schematics, I don't remember wich one it is, but is easy to find out

Re: Fulltone - OCD

PostPosted: 28 Sep 2012, 02:31
by jymaze
Just a correction to the statement above:

Quote: "There's just one capacitor (one of the 10uF's) is Tantalum, the others are film capacitors."

The big polar capacitors of 10uF or more are electrolytics, except C7 that is tantalum (electrolytic here would be just as good).

Actually tantalum capacitors are the worst thing for signal (huge hysteresis) so even an electrolytic for C7 is better in that respect.

Re: Fulltone - OCD

PostPosted: 28 Sep 2012, 11:15
by Branimir
Hm, I've never actually payed attention to capacitors, I used polypropylene capacitors, does film capacitor means polyester capacitor in this case, and does it really matter? 8)

Re: Fulltone - OCD

PostPosted: 28 Sep 2012, 13:57
by jymaze
Polyester are the cheapest of films caps so that is what is used usually (versus polypropylene, polycarbonate or polystyrene). It does not matter that much anyway for guitar application, just take the cheapest. At least, I would avoid tantalum for sure.

Re: Fulltone - OCD

PostPosted: 28 Sep 2012, 17:20
by batteryacidtea
jymaze wrote:Just a correction to the statement above:

Quote: "There's just one capacitor (one of the 10uF's) is Tantalum, the others are film capacitors."

The big polar capacitors of 10uF or more are electrolytics, except C7 that is tantalum (electrolytic here would be just as good).

Actually tantalum capacitors are the worst thing for signal (huge hysteresis) so even an electrolytic for C7 is better in that respect.


I was refering to the polarized ones, now I see I didn't answered the question properly. The pF values are ceramic, the nF values are greenies and the polarized caps are eletrolytic, just C7 (as jymaze stated above) is tantalum

Re: Fulltone - OCD

PostPosted: 28 Sep 2012, 17:55
by Branimir
I never really payed attention to the caps, I just bought the ones that are available, okay so it's not critical to use that tantalum after all... Though I'm stupid, I have tried the V4 original and built mine and frankly, they sound the same, I just don't have them next to each other to A/B them properly.

Re: Fulltone - OCD

PostPosted: 22 Aug 2015, 03:28
by Intripped
Just wanted to put some light on how exactly the clipping transistors and the germ. diode are connected.
I have a V4 here on my bench and I see that Source and Gate are connected together (trannies are 2n7000).
So we have S+G and D, where D corresponds to the striped end of a normal diode.

---->|---[S+G] [D]----
This represents how the germ diode and the 2n7000 are connected in series

Re: Fulltone - OCD

PostPosted: 22 Aug 2015, 17:07
by howmuch
Intripped wrote:Just wanted to put some light on how exactly the clipping transistors and the germ. diode are connected.
I have a V4 here on my bench and I see that Source and Gate are connected together (trannies are 2n7000).
So we have S+G and D, where D corresponds to the striped end of a normal diode.

---->|---[S+G] [D]----
This represents how the germ diode and the 2n7000 are connected in series

Thanks for posting some first hand evidence on the connections.
It still seems to be widely (and wrongly IMHO) accepted that the gate is connected to the drain (as in the schematic yongki posted above), even though people have hinted otherwise earlier in this thread.
So does your OCD have the same clipping configuration as the Joyo clone's corrected circuit I posted here - the "Circuit when D2 is in the "correct" orientation"?
Image

You've got ---->|---[S+G] [D]---- and the corrected Joyo is electrically the same with ----[S+G] [D]---->|---
Or put another way, on the schematic yongki posted above, move the gate connections from the drains to the sources?

Re: Fulltone - OCD

PostPosted: 22 Aug 2015, 19:25
by Intripped
howmuch wrote:So does your OCD have the same clipping configuration as the Joyo clone's corrected circuit I posted here - the "Circuit when D2 is in the "correct" orientation"?
[ Image ]

You've got ---->|---[S+G] [D]---- and the corrected Joyo is electrically the same with ----[S+G] [D]---->|---
Or put another way, on the schematic yongki posted above, move the gate connections from the drains to the sources?



YES to all

...and to avoid any further confusion, here is the exact clipping section:

Re: Fulltone - OCD

PostPosted: 26 Jul 2016, 13:04
by SamBloody
Hi guys!
Can you give me verified fulltone ocd pcb layout?
Thanks!

Re: Fulltone - OCD

PostPosted: 26 Jul 2016, 16:59
by storyboardist
Here's my layout.

Image

Re: Fulltone - OCD

PostPosted: 26 Jul 2016, 17:19
by 287m
Nice layout David :thumbsup
perfect for 1590B

so i present to 1590A Club masochist :mrgreen:
Image
reff sch https://4.bp.blogspot.com/-G_jLNr0ZECI/V5eM7fNInjI/AAAAAAAAALU/-A2SqlvuXIImWgGU-js1ryFJmnahiw1IACLcB/s1600/ocd-sch.png

Re: Fulltone - OCD

PostPosted: 26 Jul 2016, 18:55
by SamBloody
Thank you,guys!

Re: Fulltone - OCD

PostPosted: 18 Aug 2016, 11:22
by V1nce69
Hi all,

I own an OCD #84590 with a pcb revision 1.4. Wanting to know how it works, I traced the complete pcb and made a drawing out of it. Here are a few pics and my drawing.

It might be of some interest.

IMG_0804_small.jpg


IMG_0805_small.jpg


IMG_4523_small.jpg


IMG_4524_small.jpg


OCD_pcb-layout-1.4.jpg

Re: Fulltone - OCD

PostPosted: 18 Aug 2016, 14:38
by Intripped
nice work!
just a little note:
in your drawing, 2N7000 pins are named wrong