Fulltone - OCD  [traced]

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Post by Blend »

I agree, it now also works in front of the gain pedals or a high gain channel and the output buffer keeps a neutral sound in combination with the chain pedals. It has a low gain sound like a tube blow with the increase in average frequencies compared to previous OCD versions while distortion loses the previous bite. I would not remove the smooth germanium diode.

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Post by 287m »

so its just a OCD plus buffer? hahaha
i just covered some year ago when OCD going to Carbon Delay, make vomit.
just add buffer i found in cazilt oldcraft blog, smile again. hahaha

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Post by ggbb »

Is that correct - the new version has no input cap going into Q5?

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Post by Ichabod_Crane »

I saw this document linked, more than one time: http://www.fulltone.com/PDfFiles/OCD%20 ... _small.pdf But there's no anymore.
May someone link it again, please? :thumbsup

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Post by ggbb »

Ichabod_Crane wrote:I saw this document linked, more than one time: http://www.fulltone.com/PDfFiles/OCD%20 ... _small.pdf But there's no anymore.
May someone link it again, please? :thumbsup

That document is old and out of date anyway. It only covers up to "version 3" and all of the information is documented elsewhere on the web. But for those who want it: https://web.archive.org/web/20081209114 ... _small.pdf.

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Post by Ichabod_Crane »

Thank you.
Indeed it was old, further I found it somewhere else but I didn't know that it was the same I had. :oops:

8)

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Post by Ichabod_Crane »

Excuse me, I didn't really get the OCD V2.0 schematic.
I identified the original OCD section, it just includes some mods and a kind of output stage Tube Screamer type. It's useful to get the OCD more friendly with other pedals, especially those buffered. Right?

There's a switch, and you can choose EB if want to use the buffer when the pedal is engaged or not engaged, or you can choose TB if you want omit the buffer and make the pedal true bypass as the older version.

I can't understand, in the schematic above, the route and the connection of the signal through the first switch, that two buffers stage and the input of the OCD. :scratch:

Thanks!

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Post by bucksears »

A couple of questions, since I've never really been into OCDs until recently.

1) Heard a demo of the 1.6 or 1.7 version last night (comparing it to a DLS III) and was wondering if there are schems for those anywhere. I've only seen info for v1.0 thru 1.4.
2) Is there an audio comparison/description of the different versions? I'm looking for whichever one(s) have the most mids.

Thanks!
- Buck

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Post by Ichabod_Crane »

Hello.
I am in a full immersion of the Fulltone OCD (and surroundings) schematic. :D
I guess there's a bit of confusion about the different release of the OCD. The people know the several versions called V1, V2, V3 e V4. I want to exclude the very last release 2.0: a bit different.
The changes are the tone cap and the three pots, and of course the germanium diode. The V4 should be the 1.4, that should be very similar to the 1.6 and 1.7 versions.

In my opinion, folllowing all the info I found in the web, the trackers are ignored the power supply, where we can find a diode instead of a 100R resistor, which limit the voltage, plus another diode across the ground. And, probably, a 47uF 0r 100uF cap filter, where about this, I found a comment by Mike Fuller by Fulltone.
And even a bit detail maybe is "missed", Indeed I suspect we could find in the 1.7 version of the OCD not a 500k Volume pot as we can see in the known schematic of the V4. Some images of the 1.7 PCB version shows, after the volume pot changed from 100k to 500k in the V2, the pot is back again to the 100k, initially linear, and only later log.

There's another suspect cap changed, a cap lowered in the feedback loop of the opamp to cut the bass. I read it around, but I didn't see in any schematic.

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Post by jhergonz »

Ichabod_Crane wrote:Excuse me, I didn't really get the OCD V2.0 schematic.
I identified the original OCD section, it just includes some mods and a kind of output stage Tube Screamer type. It's useful to get the OCD more friendly with other pedals, especially those buffered. Right?

There's a switch, and you can choose EB if want to use the buffer when the pedal is engaged or not engaged, or you can choose TB if you want omit the buffer and make the pedal true bypass as the older version.

I can't understand, in the schematic above, the route and the connection of the signal through the first switch, that two buffers stage and the input of the OCD. :scratch:

Thanks!

maybe the SW2.2 is the DPDT switch for Eenhanced/TB modes, maybe if you choose TB mode the signal will go straight to C1?

I'am also confuse about how the switching works. Please somebody explain or revise the scheme?

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Post by gsb »

Hi,
Friend have OCD V2.O with strange behavior.Led is not working with 9v .Pedal works fine .On 18v led is always on.I think it must be switch?
Thanks for advice

gsb

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Post by Seiche »

LED Resistor too big?

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Post by Manfred »

gsb wrote:Hi,
Friend have OCD V2.O with strange behavior.Led is not working with 9v .Pedal works fine .On 18v led is always on.I think it must be switch?
Thanks for advice
gsb
The PCB layout version 1.7 shows three transistors, the BJT is used for the LED switching circuit,
in accordance with the schematic below.
I guess in version 2.0 this circuit has been retained
This transistor could also be defective.

Image

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Post by gsb »

Hi Manfred ,
Thanks for advice ,i will check transistor. What kind of transistor - bs250 ..is on pcb on site 27.
gsb

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Post by Manfred »

gsb wrote:Hi Manfred ,
Thanks for advice ,i will check transistor. What kind of transistor - bs250 ..is on pcb on site 27.
gsb
This layout shows that the LED switching circuit is not retained in version 2.0
I drew the switching schematic according with the layout on site 27.
BS250_LedSwitch.JPG

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Post by Manfred »

I ran a simulation of this switching circuit, but the switching do not work.
I change the +9VDC on the switch terminal to ground, no it works using in a supply voltage range from 9VDC to 18VDC.
It seems that the connection between 9VDC and the terminal of the stomp switch in the layout on site 27 is not correct.
BS250_LedSwitchCorrected.JPG

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Post by Manfred »

The simualtion gives a current flow through the LED of 0.3 to 1 Amps with an supply voltage from 9 to 18 Volts,
which is definitely to high.
If the layout und thus the schematic correct, then the LED must be a type with integrated series resistor for a commom LED current.
On the other hand the schematic could be wrong.
Who knows more about this LED swithing circuit.
Hi,
Friend have OCD V2.O with strange behavior.Led is not working with 9v .Pedal works fine .On 18v led is always on.I think it must be switch?
Thanks for advice

gsb
Hi gsb,
Could you verify the schematic respectively the layout with the aid of your friends OCD?

This circuit works with a suitable LED current.
BS250_LedSwitchCorrected2.JPG

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Post by gsb »

Hi,
Ok ,I make some pictures of pedal ,to see how is led wired
Thanks
gsb

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Post by plush »

Manfred, reminds me of yer old millenium bypass
Attachments
yoloswagbypass.png

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Post by gsb »

Hi,
Here some pictures ,all SMD.Q1 transistor is marked with MX. I have played one more time -pedal works fine all controls are fine ,no led .I have check voltages on q1 . Measured voltage about 9,06v pin2 -S,8,6v on pin 3 -D and 9,06 on pin 1 G. Voltages are equal in off and on mode!! I think it must be Q1 ?
gsb
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IMG_20181115_210003 (577 x 1024).jpg

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