Fulltone - 2B  [traced]

General documentation, gut shot, schematic links, ongoing circuit tracing, deep thoughts ... all about boutique stompboxes.
User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

I have one of these here for a week or so. I'm kind of working on a schematic but any help would be appreciated. I'll take pics of anything you want and try and help with any values/info you need.
Here are some pics. If there is interest in this I will continue with the schematic and post it. Don't really want to post a unverified, unfinished schematic. I'll try and post some values later.
20190510_105853sm.jpg
20190510_105900sm.jpg
20190521_093222sm.jpg
20190521_093226sm.jpg
20190521_093230sm.jpg
20190521_093234sm.jpg
20190521_093258sm.jpg
20190521_093302sm.jpg
20190521_093304sm.jpg
20190521_093306sm.jpg

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

Here are the values I came up with. I think I got everything. If not, let me know and I'll get it. The IC is sanded so I don't know what it is. It's a single op-amp. I don't see any value markings on the Gain pot.

R1 10K
R7 3M3
R15 10K
R20 3M3
R22 10K
R23 10K
R26 100E
R27 100K
R29 4K7
R30 1K

C? 0.1uF (Bigger reddish cap in the middle. No reference that I can see)
C7 100uF/25v
C13 100uF/25v
C14 10u/35v
C15 10uF/35v
C16 100pF

D3 1N4005
D4 1N5818
D5 5mm LED
D9 1N750A
D13 Germ
D14 Germ

U3 ? Sanded Single Op-Amp
Q4 BS250

DYNAMICS B-250K
GAIN ? Measures 60K In Circuit

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

In the parts/values list above I wrote R20 and it should be R28. I didn't have my glasses on and the 8 looked like a 0. :D

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

Here's the schematic. Maybe this will spark more interest in this. I'm pretty sure it's correct but I have the pedal for a few more days so if you have any doubts/questions I'll check them.
2Bv1.0.pdf
(28.38 KiB) Downloaded 1002 times

User avatar
Intripped
Cap Cooler
Information
Posts: 670
Joined: 25 Aug 2009, 01:03
Location: Italy
Has thanked: 989 times
Been thanked: 305 times

Post by Intripped »

Hey, thanks for your work!
the gain pot value: you should be able to measure it, if you lift one end of R30; but I see they have bent the legs of all components under the PCB, and this could result in some complications in the desoldering process.
You could try and unbend the component legs while desoldering, but probably the safest way is to just cut the legs and then use a new resistor.

Good to know, that this pedal is not true bypass, and that it becomes a buffer when bypassed.
A nice test that you could make, is to hear and evaluate the "transparency" (or tonal influence) of this buffer.

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

Intripped wrote:Hey, thanks for your work!
the gain pot value: you should be able to measure it, if you lift one end of R30; but I see they have bent the legs of all components under the PCB, and this could result in some complications in the desoldering process.
You could try and unbend the component legs while desoldering, but probably the safest way is to just cut the legs and then use a new resistor.

Good to know, that this pedal is not true bypass, and that it becomes a buffer when bypassed.
A nice test that you could make, is to hear and evaluate the "transparency" (or tonal influence) of this buffer.
It's not my pedal so I didn't really want to mess with it too much. I'll see if I can lift the leg of that resistor and see what I measure. It didn't seem like there was much resistance in series or parallel with it so I didn't think too bother too much
with it.

User avatar
Intripped
Cap Cooler
Information
Posts: 670
Joined: 25 Aug 2009, 01:03
Location: Italy
Has thanked: 989 times
Been thanked: 305 times

Post by Intripped »

Bside2234 wrote: It's not my pedal so I didn't really want to mess with it too much. I'll see if I can lift the leg of that resistor and see what I measure. It didn't seem like there was much resistance in series or parallel with it so I didn't think too bother too much
with it.
Pay attention, you could damage the PCB, because of that bent leg.
Resistor substitution it's the safest way, if you really want to do it.

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

The Gain pot measures 100K exactly with R30 removed.

User avatar
ahauser
Information
Posts: 4
Joined: 17 Jun 2019, 00:55
Been thanked: 2 times

Post by ahauser »

Hi Bside,
Were you able to identify the Germanium Diodes?
Thanks.

User avatar
ahauser
Information
Posts: 4
Joined: 17 Jun 2019, 00:55
Been thanked: 2 times

Post by ahauser »

I had a look in the FD 3 as the boost is apparently the same. The 2 ICs in it are
2072C and AD711J

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

ahauser wrote:Hi Bside,
Were you able to identify the Germanium Diodes?
Thanks.
No. There weren't any markings on them.

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

ahauser wrote:I had a look in the FD 3 as the boost is apparently the same. The 2 ICs in it are
2072C and AD711J
Not familiar with the 2072C. Is that the TLE2072? Link to a datasheet?

User avatar
ahauser
Information
Posts: 4
Joined: 17 Jun 2019, 00:55
Been thanked: 2 times

Post by ahauser »

It has a texas Instruments logo on it so im assuming its this one.
http://www.ti.com/product/TLE2072

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

ahauser wrote:It has a texas Instruments logo on it so im assuming its this one.
http://www.ti.com/product/TLE2072
So then we can assume the 2B uses the AD711J since it's a single op-amp in there and the TLE2072 is a dual.

User avatar
ahauser
Information
Posts: 4
Joined: 17 Jun 2019, 00:55
Been thanked: 2 times

Post by ahauser »

Hi BSide,
Re the IN750A diodes can I substitute with a 4.7V IN5230B? I cant find any IN750A's.
Also what do you suggest for the Germanuim Diodes?
Adrian

User avatar
Bside2234
Resistor Ronker
Information
Posts: 260
Joined: 30 Jul 2007, 19:35
Location: Kennewick, WA
Has thanked: 10 times
Been thanked: 89 times

Post by Bside2234 »

ahauser wrote:Hi BSide,
Re the IN750A diodes can I substitute with a 4.7V IN5230B? I cant find any IN750A's.
Also what do you suggest for the Germanuim Diodes?
Adrian
I would assume any 4.7v would work in this application. For reference the 1N750 is a 0.5W/4.7V zener diode. I'd probably start with a 1N34A for the Germanium diodes. Probably socket them and see if there is any difference between others.

User avatar
okgb
Diode Debunker
Information
Posts: 768
Joined: 16 Mar 2010, 03:58
Has thanked: 226 times
Been thanked: 38 times

Post by okgb »

Yep he's looking for his own magic diodes so he can be better than Bill! , Doe's this remind anyone of Jack & the bean stock ?

User avatar
dtp
Information
Posts: 1
Joined: 26 Apr 2014, 00:21
Has thanked: 1 time

Post by dtp »

Yay! I've been wanting a schematic of this for a long time! I love to the boost section of my FD3, but the rest of the pedal is only kinda meh...

Thanks for posting this!

User avatar
Optical
Breadboard Brother
Information
Posts: 125
Joined: 28 Jul 2016, 22:44
Location: Auckland
Has thanked: 16 times
Been thanked: 17 times

Post by Optical »

Cool, the VFE dragon uses a clipping/compression circuit just like this but with BS170 body diodes as instead of the germaniums

User avatar
Intripped
Cap Cooler
Information
Posts: 670
Joined: 25 Aug 2009, 01:03
Location: Italy
Has thanked: 989 times
Been thanked: 305 times

Post by Intripped »

from what i can see from the pics, C16 should be connected like this:
Attachments
2B - corrected.png

Post Reply