FuzzDog Tone Bender Mk II User manual

Tone Bender Mk II
Sweet, smooth fuzz
Contents of this document are ©2021 Pedal Parts td.
No reproduction permitted without the express written
permission of Pedal Parts td. All rights reserved.

Important notes
If you’re usin any of our footswitch dau hterboards,
DOWNLOAD THE DAUGHTERBOARD DOCUMENT
•Download and read the appropriate build document for the daughterboard
as well as this one BEFORE you start.
•DO NOT solder the supplied Current imiting Resistor (C R) to the main
circuit board even if there is a place for it. This should be soldered to the
footswitch daughterboard.
POWER SUPPLY
Unless otherwise stated in this document this circuit is designed to be
powered with 9V DC.
COMPONENT SPECS
Unless otherwise stated in this document:
•Resistors should be 0.25W. You can use those with higher ratings but
check the physical size of them.
•Electrolytics caps should be at least 25V for 9V circuits, 35V for 18V
circuits. Again, check physical size if using higher ratings.
LAYOUT CONVENTIONS
Unless otherwise stated in this document, the following are used:
•Electrolytic capacitors:
ong leg (anode) to square pad.
•Diodes/LEDs:
Striped leg (cathode) to square pad. Short leg to square pad for EDs.
•ICs:
Square pad indicates pin 1.

Schematic - PNP (posi ground)
R1 100K / 10K
R2 10K
R4 470R
R5 100K
C1 10n / 15n
C2 4.7u / 10u
C3 100n
C4 47u
C5 10n / 15n
C6 4.7u / 10u
Q1,2,3 PNP Germaniums
ATTACK 1KB
VO 100KA
T1 100K preset
T2 10K preset
Values in black are for the Tonebender Pro
MkII. Substitute values in blue for Marshall
SuperFuzz or red for Vox Tone Bender MkII.
The schematic above shows the original PNP
- Positive-Ground layout, which is also how
the PCB is designed. What does that mean?
Well, basically it means it won’t play nicely
with ‘normal’ pedals if you try to daisy chain
them on the same power supply. Don’t do it.
It’s perfectly simple to make a NPN -
Negative-Ground version. Use NPN
transistors, flip the orientation/polarity of C2,
C4 and C6, then follow the appropriate wiring
diagram later in these instructions. The -V
connection becomes +V.
Typical hFE ranges for the transistors are:
Q1 - 55-60 Q2 - 70-80 Q3 - 100-140

The power and signal pads on the PCB
conform to the FuzzDog Direct Connection
format, so can be paired with the appropriate
daughterboard for quick and easy offboard
wiring. Check the separate daughterboard
document for details.
Be very careful when soldering the transistors
if you aren’t using sockets (why not?). They’re
very sensitive to heat. You should use some
kind of heat sink (crocodile clip or reverse
action tweezers) on each leg as you solder
them. Keep exposure to heat to a minimum
(under 2 seconds).
Snap the small metal tag off the pots so they
can be mounted flush in the box.
You should solder all other board-mounted
components before you solder the pots. Once
they’re in place you’ll have no access to much
of the board.
Trimmers should mount on the same side of
the PCB as the pots, as shown.
Once everything is soldered in place you
need to adjust the trimmers to bias the
transistors. Q1 is fixed bias, but you
adjust T1 and T2 to change the voltages
on the collectors of Q2 and Q3 respectively
(marked above).
There are no definitive ‘correct’ voltages, but
you should be in the ballpark of:
Q2 - 1.0 - 1.75V
Q3 - 8.0 - 8.5V
Set Q2’s bias first before tweaking Q3, as the
T1 trimmer will affect both.
It’s a case of tweaking by ear within those
ranges until you get the sound you want.
Sweet, sustained fuzz without gating.
PCB layout ©2018 Pedal Parts td.

Test the board - PNP version
UNDER NO CIRCUMSTANCES will troubleshootin help
be offered if you have skipped this sta e. No exceptions.
Once you’ve finished the circuit it makes sense to test is before starting on the switch and ED
wiring. It’ll cut down troubleshooting time in the long run. If the circuit works at this stage, but it
doesn’t once you wire up the switch - guess what? You’ve probably made a mistake with the switch.
Solder some nice, long lengths of wire to the board connections for -V, GND, IN and OUT. Connect
IN and OUT to the jacks as shown. Connect all the GNDs together (twist them up and add a small
amount of solder to tack it). Connect the battery - lead to the -V wire, same method. Plug in. Go!
It may look strange, but as this is a positive ground circuit the +9V power goes to the GND of the
circuit and the jacks.
If you’re using a ribbon cable you can tack the wires to the ends of that. It’s a lot easier to take them
off there than it is do desolder wires from the PCB pads. Check the daughterboard doc for details.
If it works, carry on and do your switch wiring. If not... aw man. At least you know the problem is
with the circuit. Find out why, get it working, THEN worry about the switch etc.
Your completed circuit board
includin pots

Test the board - NPN version
UNDER NO CIRCUMSTANCES will troubleshootin help
be offered if you have skipped this sta e. No exceptions.
Once you’ve finished the circuit it makes sense to test is before starting on the switch and ED
wiring. It’ll cut down troubleshooting time in the long run. If the circuit works at this stage, but it
doesn’t once you wire up the switch - guess what? You’ve probably made a mistake with the switch.
Solder some nice, long lengths of wire to the board connections for -V, GND, IN and OUT. Connect
IN and OUT to the jacks as shown. Connect all the GNDs together (twist them up and add a small
amount of solder to tack it). Connect the battery + lead to the -V wire, same method. Plug in. Go!
If you’re using a ribbon cable you can tack the wires to the ends of that. It’s a lot easier to take them
off there than it is do desolder wires from the PCB pads. Check the daughterboard doc for details.
If it works, carry on and do your switch wiring. If not... aw man. At least you know the problem is
with the circuit. Find out why, get it working, THEN worry about the switch etc.
Your completed circuit board
includin pots

Wiring shown above will disconnect the battery when you remove the jack plug
from the input, and also when a DC plug is inserted.
The Board GND connections don’t all have to directly attach to the board. You
can run a couple of wires from the DC connector, one to the board, another to
the IN jack, then daisy chain that over to the OUT jack.
It doesn’t matter how they all connect, as long as they do.
This circuit is standard, Negative GND. Your power supply should be Tip
Negative / Sleeve Positive. That’s the same as your standard pedals (Boss etc),
and you can safely daisy-chain your supply to this pedal.
BOARD
OUT
BOARD
-9V
BOARD
GND
BOARD
GND
BOARD
INPUT
BATTERY
IN
OUT
BOARD
GND
+
L
E
D
+L
E
D
BOARD
-9V
Wire it up - PNP
(if using a daughterboard please refer to the relevant document)

Wiring shown above will disconnect the battery when you remove the jack plug
from the input, and also when a DC plug is inserted.
The Board GND connections don’t all have to directly attach to the board. You
can run a couple of wires from the DC connector, one to the board, another to
the IN jack, then daisy chain that over to the OUT jack.
It doesn’t matter how they all connect, as long as they do.
This circuit is standard, Negative GND. Your power supply should be Tip
Negative / Sleeve Positive. That’s the same as your standard pedals (Boss etc),
and you can safely daisy-chain your supply to this pedal.
L
E
D
BOARD
OUT
BOARD
9V
BOARD
GND
BOARD
GND
BOARD
GND
BOARD
INPUT
BATTERY
+
IN
OUT
L
E
D
BOARD
GND
BOARD
9V
+
Wire it up - NPN
(if using a daughterboard please refer to the relevant document)

This template is a rough guide only. You should ensure correct marking of your
enclosure before drilling. You use this template at your own risk.
Pedal Parts td can accept no responsibility for incorrect drilling of enclosures.
FuzzDog.co.uk
Drilling template
Hammond 1590B
60 x 111 x 31mm
It’s a good idea to drill the pot and
toggle switch holes 1mm bigger i
you’re board-mounting them.
Wiggle room = good!
Recommended drill sizes:
Pots 7mm
Jacks 10mm
Footswitch 12mm
DC Socket 12mm
Toggle switches 6mm
32mm