Fulltone - OCD  [traced]

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Manfred
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Post by Manfred »

gsb wrote: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
Or perhaps the connection to the switch.
Could you please trace the switching circuit?

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Post by gsb »

hi,
I dont work usualy with SMD ,Friend need the drive ,i have disabled q1 and put bs250 in and shorted the legs .Now led is working .I hate fu....g SMD.Sorry i cant trace this build.Pedal is working very good .
thanks for help
gsb

Manfred
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Post by Manfred »

gsb wrote:hi,
I dont work usualy with SMD ,Friend need the drive ,i have disabled q1 and put bs250 in and shorted the legs .Now led is working .I hate fu....g SMD.Sorry i cant trace this build.Pedal is working very good .
thanks for help
gsb
The main thing is, the LED is working again.
I agree with you in SMDs.

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x-tn
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Post by x-tn »

https://www.fulltone.com/products/custom-shop-cs-ocd-ge

"The earliest OCDs used 2 x Mosfets plus 1 x Germanium diode, but very quickly these diodes became harder and harder to find, and they became expensive.

Recently I stumbled across a reasonably large stash of the right kind of Germanium diodes so I ponied-up and bought all of them. I then decided to do a small run of the ultimate OCD: a Custom Shop offering with a few circuit tweaks, 2 x Mosfets plus 2 x Germanium diodes...

The sound? Great definition, more tube-like feel, a bit wider dynamic range, more sustain, and a more focused single-note tone."

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Post by caspercody »

So do they have a GE per MOSFET for the clipping? With orientation opposite of each other?

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Post by Cigla tel. »

x-tn wrote:https://www.fulltone.com/products/custom-shop-cs-ocd-ge

"The earliest OCDs used 2 x Mosfets plus 1 x Germanium diode, ....................
.........................

The sound? Great definition, more tube-like feel, a bit wider dynamic range, more sustain, and a more focused single-note tone."
Do you believe in these fairy tales? :lol:

The title talks everything: "COMING SOON!.. The Fulltone Custom Shop CS-OCD-Ge."!

IN TRANSLATION: "It's time to fooling the fool"!!!

:lol:

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Post by rpc66 »

caspercody wrote:So do they have a GE per MOSFET for the clipping? With orientation opposite of each other?
Ditto
Is the OCD-GE the same as the original but with an added diode? And is it in-line with the first MOSFET?

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Post by Bernardduur »

OCD V2 LED sw.JPG
Here's the LED switching part of the OCD V2.0

I don't know the value of D4 and C19

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plush
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Post by plush »

Bernardduur wrote:
OCD V2 LED sw.JPG
Here's the LED switching part of the OCD V2.0

I don't know the value of D4 and C19

Greetings!!

D4 is a schottky diode, 3v3, 5v6 or so. Must be much lower than supply voltage to operate correctly.
C19 together with R23 controls the speed of switching, I beleive, it's something in between 1n and 22n.

The whole point of this circuit is to smooth led switching (and possibly mitigate popping nose which is not the case here). Seems more like a remnant, than a feature.

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Post by mictester »

plush wrote:
D4 is a schottky diode, 3v3, 5v6 or so.
Nope. You mean ZENER diode. A Schottky diode is a completely different beast - low forward voltage drop and low reverse leakage.

A zener diode is designed to be used reverse biased, and when the marked threshold voltage is reached, it starts to conduct.
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Post by plush »

mictester wrote:
plush wrote:
D4 is a schottky diode, 3v3, 5v6 or so.
Nope. You mean ZENER diode. A Schottky diode is a completely different beast - low forward voltage drop and low reverse leakage.

A zener diode is designed to be used reverse biased, and when the marked threshold voltage is reached, it starts to conduct.
Yeah, zener, of course.

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