Mod WAHTZ WAH K-985 User manual

1Copyright © 2016 by modkitsdiy.com
Use these instructions to learn:
How to build a wah-wah pedal
The Wahtz Wah Pedal produces the classic wah tone you've come to expect with a hint of extra bite and
growl. True bypass switching insures no loss of signal when the wah effect is not engaged, and the long life
potentiometer manufactured specifically for use in wah pedals is included to provide years of smooth, quiet
operation. Point to point construction allows advanced kit builders to easily experiment with modifications to
further tailor the tone to more individual tastes.
THE WAHTZ WAH (K-985)
Warning: This circuit was designed for use with a 9 VDC power supply only.
9 VDC
CENTER (-)
ADAPTER
Output
Jack
Unplug from the Wahtz input
jack (other side) when not in
use to save battery life.

2
Visit www.modkitsdiy.com if you have any problems when first turning on your pedal for
troubleshooting help. Remember to use caution when applying power to the pedal to avoid electric
shock.
TOOL LIST
Wire Strippers
Needle Nose Pliers
Cutting Pliers
Desoldering Pump
Solder (60/40 rosin core)
Soldering Station
Phillips Head Screwdrivers
Channellock Pliers (or similar type)
Ruler
Contact Cement or RTV Silicone Adhesive
Small Hammer
Small Metal File or Course Grit Emery Cloth (to clean off flash on some pedal parts)
½" Nut Driver or Small Adjustable Wrench (to tighten the input and output jacks)
¼" Pin Punch (to insert the bearing pin)
5mm Allen Wrench (to tighten the tension adjustment screw)
12 mm Wrench (to fasten the wah pot in its mounting bracket)
Contact Cement or other adhesive (to secure the tread and pedal bumpers)
TABLE OF CONTENTS
TOOL LIST p. 2
PARTS LIST DRAWINGS pp. 3 - 5
Wah Shell Parts p. 3
Electronic Components & Additional Hardware p. 4
SOLDERING TIPS p. 6
STEP BY STEP ASSEMBLY INSTRUCTIONS pp. 7 - 13
Section 1 - Wah Shell Assembly p. 7
Section 2 - Mounting Large Components to the Base p. 8
Section 3 - Final Assembly of Pedal Base and Treadle p. 9
Section 4 - Wiring the Jacks, Pots, Footswitch and Terminal Strips p. 10
Section 5 - Mounting the Components p. 10
Section 6 - Final Assembly p. 12
Adjustment of the Footswitch Height p. 13
Fixing a Squeaky Wah p. 13
ASSEMBLY DRAWINGS (3 Drawings) pp. 14 - 16
These are the last 3 pages. They should be used as a reference for assembly.

3
PARTS LIST 1
Mounting Screws (4)
(M3 x 0.5, L = 10 mm)
Rubber Feet,
Tapered
(4)
L-bracket (1)
Mounting Nuts (2)
(M4 x 0.70)
Washers (2)
Center Pillow Block &
Tension Adjustment
Screw
(1)
Bearing Pin (1)
Rear Bumper (1)
Front Bumpers (2)
Bottom Cover (1)
Wah Base (1)
Treadle (1)
Rubber Tread (1)
Mounting Screws (2)
(M4 x 0.70, L = 16 mm)
Rack Assembly Parts:
Rack (1)
Small Screw (1)
(M3 x 0.5, L = 12 mm)
Hex Nut (1)
(M3 x 0.5)
Split Lock Washer (3)
Rack mount (1)
Self-Tapping Screws (3)
Rack Tensioner (1)
(1)
P-ECB-RACK
#6 Internal Tooth Lock
Washer
S-HLW6
R-VWAH-POT (1)
100K Wah Pot
Felt Switch Pad (1)
K-PWAH-FELT

4
103K
400V
0.01µF Capacitor 400V
C-TD01-400 (2)
0.22µF Capacitor 100V
C-PEID22-100 (2)
224J
K-PC4D7-35 (1)
4.7µF Polarized Capacitor 35V
4.7µF35V
P-Q2N5088 (2)
NPN BJT (2N5088)
2N
5088
E B C
Stranded Wire (22 AWG) - White
K-PUL1569-WHITE (5 FT)
P-ECB-156 (1)
Inductor - 500 mH
Terminal Strip with 8 Terminals
P-0802H (2)
Terminal Strip with 2 Terminals
P-0201H (1)
Terminal Strip with 5 Terminals
P-0501H (1)
DPDT Foot Switch
P-H498 (1)
Battery Clip
S-H155 (1)
#4 Screws (3/8" long)
S-HS440-38 (6)
#4 Nuts
S-HHN440 (6)
#4 Lock Washers
S-HLW4 (6)
¼” Mono Jack (Output Jack)
W-SC-11-T (1)
¼” Stereo Jack (Input Jack)
W-SC-12B (1)
RING LUG
GROUND LUG
TIP LUG
GROUND LUG
TIP LUG
(2)
Double Sided Adhesive
Foam Tape
(1)
Foam Battery Cushion
PARTS LIST 2
DC Power Jack
S-H750 (1)

R-A470K (2)
470kΩ Resistor ½ W
yellow
violet
yellow
gold
470K
R-A270 (1)
270 Ω Resistor ½ W
red
violet
brown
gold
270
R-A1K (1)
1kΩ Resistor ½ W
brown
black
red
gold
1K
R-A1D5K (1)
1.5kΩ Resistor ½ W
brown
green
red
gold
1.5K
R-A10K (1)
10kΩ Resistor ½ W
brown
black
orange
gold
10K
R-A22K (1)
22kΩ Resistor ½ W
red
red
orange
gold
22K
R-A33K (1)
33kΩ Resistor ½ W
orange
orange
orange
gold
33K
R-A68K (1)
68kΩ Resistor ½ W
blue
grey
orange
gold
68K
R-A100K (1)
100kΩ Resistor ½ W
brown
black
yellow
gold
100K
5
PARTS LIST 3

SOLDERING TIPS
1. Bend the component lead
and wrap it around the
connection point.
2. Wrap the component lead
so that it can hold itself to the
connection point.
3. Heat up both component
lead and connection point with
the soldering iron.
4. Apply solder to both
component lead and
connection point.
2. Apply fresh solder to mix in
with old solder joint
1. Heat up old solder joint
with the soldering iron.
3. Use a de-soldering tool to
remove the old solder joint
while it is heated.
De-Soldering Tip
6
It is important to make a good solder joint at each connection point. A cold solder joint is a connection that
may look connected but is actually disconnected or intermittently connected. (A cold solder joint can keep
your project from working.)
Follow these tips to make a good solder joint. Take your time with each connection and make sure that all
components are connected and will remain connected if your project is bumped or shaken.
Bend the component lead or wire ending and wrap it around the connection point.
Make sure it is not too close to a neighboring component which could cause an
unintended connection.
2. Wrap the component lead so that it can hold itself to the connection point.
Touch the soldering iron to both the component lead and the connection point allowing both to
warm up just before applying the solder to them.
Be sure to adequately cover both component lead and connection point with melted solder.
Remove the soldering iron from your work and allow the solder joint to cool. (The
solder joint should be shiny and smooth after solidifying.)
Cut off any excess wire or component leads with cutting pliers.
Clean the soldering iron's tip by wiping it across the wet sponge again after making the
solder joint.

7
SECTION 1 - Wah Shell Assembly
Rack Assembly and Bumpers
Use the small screw, split lock washer and nut to attach the rack to the rack
mount with the teeth of the rack pointed toward the toe end of the treadle. The
split lock washer should be placed underneath the nut. Do not over-tighten the
nut so that the bracket can no longer swing freely.
On the treadle, use two of the self tapping screws and split lock washers to fasten the rack mount to
its mounting block in the same orientation as shown in the drawing.
It may be necessary to file off some aluminum flash from the surface of the treadle mount block surface so the rack
assembly will sit flush against the mounting block surface. (Because these are self tapping screws it will take
considerable pressure to get the screws in).
Mounting
Block
TREADLE INSIDE
SURFACE
Toe End of Treadle
Heel End of Treadle
With the Toe End of the treadle
directed away from you, fasten
the rack mount with its two
brackets oriented toward the left
side of the treadle.
Mounting
Block
Rack Mount
Lock Washer
Mounting
Block
Lock Washer
Bracket
Remove the paper backing on the felt pad and attach it to the treadle’s inside surface centered
between the two front bumper holders at the toe end. (This will cushion the footswitch when
turning the pedal on and off).
Front Bumper Holders
Remove the backing from the rear bumper and mount it in the hole on top of the holder centered
at the treadle’s heel end.
Treadle assembly is almost complete. We recommend that you wait until after completing the rest of the wah pedal
shell assembly before attaching the rubber tread to the outer surface of the treadle. It will take some time for the glue to
completely dry and it’s best not to handle the treadle while the rubber tread is still drying.
Using wire cutters or small scissors, clip off the top end of the
two front bumpers. The surface of the bottom end should be
fairly smooth, it will go into the front bumper holders.
Using contact cement or other pliable adhesive, attach the
modified front bumpers in the front bumper holders. If possible,
you should allow the adhesive to set up according to the
instructions on your adhesive before continuing assembly of the
pedal. You may want to put masking tape over them to keep
them in place if you wish to continue assembly without
interruption.
Front Bumper Modification
Top End
Cut Here
Bottom End
Keep this
surface fairly
smooth.
Bottom End
Before attaching any part with an adhesive, be sure to clean the mounting surface.
If you plan on painting the enclosure, do so prior to assembly and allow plenty of time for the paint to dry.

8
Mount the L-bracket on the outer surface of the base
using the two long 16 mm screws, nuts and flat washers
as shown in the drawing. The screws should be
inserted from the inside of the base so that the screw
heads are on the inside of the pedal.
Push the tension adjustment screw through the hole in
the L-bracket. Place the pillow block between the two
bearing pin mounts.
Bearing Pin Mount
L-bracket
The non-threaded hole in the pillow block is slightly off center. The
side of the pillow block that the non-threaded hole is closest to should
face up so that it lines up better with the two bearing pin mount holes.
0.15"
0.22"
This Side Up
Screw the tension adjustment screw part way into the
threaded hole in the pillow block.
Slide the bearing pin through the two mounts and the
pillow block as shown in the drawing. Turn the
tension adjustment screw with your fingers until its
head is flush with the back of the L-bracket. Do NOT
tighten this screw, yet. Slide the bearing pin out and
set it aside. The pillow block is now aligned for final
assembly.
BASE
OUTER
SURFACE
Mount Mount
Pillow
Block
Tension
Adjustment Screw
SECTION 2 - Mounting Large Components to the Base
Please refer to DRAWING 1
Using #4 screws, nuts and lock washers, mount the four terminal strips as shown in Drawing 1.
Mount the input jack in the hole on the left side of the base (where indicated in the drawing).
Make sure the two solder lugs are in the most upright position before tightening the nut.
Mount the output jack in the hole on the right side of the base (where indicated in the drawing).
Make sure the two solder lugs are in the most upright position before tightening the nut.
Mount the DC power jack in the 15/32" hole just below the output jack. Orient the lugs on the
DC power jack so the larger center-pin lug is facing the output jack. Tighten the DC power jack.
CENTER-PIN LUG
POSITIVE-SWITCH LUG
POSITIVE LUG
DC Power Jack

9
Mount the wah pot on its mounting bracket with solder lugs facing up as shown in Drawing 1. Be
sure to press the pot all the way down to rest against the bottom of the bracket. The pot's nut
and small flat washer will be on the input jack side of the mounting bracket. The lock washer
and two large washers will be on the output jack side of the mounting bracket. Tighten the wah
pot hardware by using a 12 mm wrench or some other tool to make sure it will stay securely in
place when the wah pedal is in use.
SECTION 3 - Final Assembly of Pedal Base and Treadle
Place the treadle on top of the base as shown in the
drawing. Make sure the rack stays inserted through the
large rectangular hole in the base. Line up the bearing pin
holes on the treadle with those on the base. Insert the
bearing pin, smooth end first, through all of the bearing pin
holes including: both treadle holes, both base mount holes
and the pillow block hole.
Using a hammer and ¼" pin punch, carefully tap the splined
end of the bearing pin into the hole until it is flush with the side
of the treadle.
Adjust the tension of the adjustment screw with a 5 mm Allen wrench so that the treadle stays in
place when you remove your foot and so that it suits your playing preference.
Base Assembly
Looking at the inside surface of the base with the toe
end directed away from you. Use the remaining self
tapping screw and internal tooth lock washer to mount
the rack tensioner to the hole as shown in the drawing.
The lock washer goes directly underneath the screw
head. (Keep this screw fastened loosely until the final
assembly stage on p. 12).
BASE
INSIDE
SURFACE
Tip: Lay the pedal on its side with a couple of magazines stacked underneath the treadle, on the side opposite from
where you will be hammering, to keep the treadle propped up from your work bench.
Bearing Pin Holes
LEFT SIDE
(with toe-end directed away from view)
Treadle
Mount the footswitch. Remove all the nuts and washers from the
footswitch and place only the lock washer on the footswitch
bushing. Insert the footswitch bushing through the ½" hole at the
toe-end of the base. Place the footswitch large nylon washer over
the bushing on the outside of the base and then screw on one of
the hex nuts. Orient the lugs on the footswitch as shown in
Drawing 1. When positioned correctly, tighten the hex nut.
Wah Base
Lock Washer
Nylon Washer
Hex Nut
Outside
Inside

10
SECTION 4 - Wiring the Jacks, Pots, Footswitch and Terminal Strips
Please refer to DRAWING 2
1) Strip and tin a 6 ½" piece of wire and connect the input jack's tip lug to footswitch lug 2.
Stripping and tinning wire: Throughout these instructions you will be told to strip and tin a length
of wire numerous times. Unless noted otherwise, cut the wire to the length stated in the
instructions. Then strip ¼” of insulation off each end. Twist each end of the stranded wire, and
apply a small amount of solder to each end (tin the wire ends). This will prevent the stranded wire
from fraying and will make the final soldering much easier.
2) Strip and tin a 6 ½" piece of wire and connect the output jack's tip lug to footswitch lug 5.
3) Strip and tin a 1 ¾" piece of wire and connect footswitch lugs 1 and 4 to each other.
4) Strip and tin a 1" piece of wire and connect pot lug 1 to terminal #22.
5) Strip and tin a 3" piece of wire and connect terminal #2 to terminal #18.
6) Strip and tin a 3 ½" piece of wire and connect terminal #3 to terminal #20.
7) Strip and tin a 6 ½" piece of wire and connect terminal #4 to pot lug 3. Do NOT solder the pot
connection, yet.
8) Strip and tin a 1 ½" piece of wire and connect pot lug 3 to footswitch lug 6. Now solder the pot
connection.
9) Strip and tin a 4 ½" piece of wire and connect terminal #10 to terminal #21.
10) Strip and tin a 5 ½" piece of wire and connect terminal #6 to terminal #23.
11) Strip and tin a 2" piece of wire and connect terminal #13 to terminal #15.
12) Strip and tin a 4" piece of wire and connect terminal #17 to footswitch lug 3.
13) Strip and tin a 1 ½" piece of wire and connect terminal #16 to the DC power jack's center-pin
lug.
14) Strip and tin a 3 ½" piece of wire and connect terminal #11 to the DC power jack's positive lug.
Tip: Wires should be routed as close to the bottom of the base enclosure as
possible in order to make mounting the components easier later in the assembly
process. Consider making wire connections to the lower terminal holes and leaving
the upper part of the terminals for component connections. lower holes
SECTION 5 - Mounting the Components
Please refer to DRAWING 3
1) Connect a .22µF cap to pot lug 2 and terminal #23.
Unless noted otherwise, “connect” means to trim the component’s leads to a reasonable length, wrap them tightly
around their connection points and solder. (See “Soldering Tips” on page 6).

11
2) Mount the inductor with double sided foam tape.
Cut a ½" x ½" piece of double sided foam tape, remove the backing from one side and press it on to
the flat side of the inductor. Remove the backing from the other side of this piece of tape and fasten
the inductor to the enclosure surface as shown in Drawing 3. Two of the inductor leads are marked
with a dot. These leads should be positioned toward the left and right sides of the enclosure. (The
inductor is not polarized so it does not matter which dot is on the left or the right). When in the
proper position, press down on the inductor to insure that it is firmly attached to the base.
Left Right
½"
3) Strip and tin a 1" piece of wire and connect terminal #21 to the marked inductor lead on the right
side of the enclosure. (Leave space for 3 more leads to be connected to terminal #21).
4) Strip and tin another 1" piece of wire and connect terminal #20 to the marked inductor lead on
the left side of the enclosure.
Tip: The best way to connect to the inductor leads is to make a U-shaped bend in one end of the
wire and crimp it around the terminal with needle nose pliers.
5) Connect the 33K resistor to terminals #20 and #21.
6) Connect the 4.7µF cap and 100K resistor to terminals #19 and #21. Make sure the (-) negative
end of the capacitor goes to terminal #19.
7) Connect the 68K resistor to terminals #17 and #18.
4.7µF35V
negative end
8) Connect a .01µF cap to terminals #2 and #15.
9) Connect the 1.5K resistor to terminals #3 and #15.
10) Connect the remaining .01µF cap to terminals #3 and #7.
lower holes
11) Connect a 470K resistor to terminal #6 and insert the other end through
the lower hole of terminal #12. Do NOT solder at terminal #12, yet. (Use
the lower hole of terminal #12 to allow for more room to connect 4 more
components to this terminal).
12) Connect the remaining 470K resistor to terminal #10 and insert the other end through the lower
hole of terminal #12. Now, solder the lower hole connections at terminal #12.
13) Connect the 1K resistor to terminals #5 and #11.
14) Connect the 10K resistor to terminals #7 and #8.
15) Connect the 22K resistor to terminals #11 and #12.
16) Connect the 270 Ω resistor to terminals #14 and #16.
17) Connect the remaining .22µF cap to terminals #4 and #12.
Mount this capacitors upside-down with the insulated top end touching the enclosure surface.

18) Mount one 2N5088 transistor to Terminals #5, #6 and #7.
Terminals #5: Collector
Terminals #6: Base
Terminals #7: Emitter
2N
5088
E B C
12
19) Mount the remaining 2N5088 transistor to Terminals #12, #13 and #14.
Terminals #12: Collector
Terminals #13: Base
Terminals #14: Emitter
2N
5088
E B C
20) Locate the battery clip. Twist its leads together a few times. Connect the black lead of the
battery clip to the input jack's ring lug. Connect the red lead of the battery clip to the power jack's
positive-switch lug.
Tip: It's always a good idea to thoroughly double check all of your connections to insure they are
properly connected and soldered before applying power for the first time.
SECTION 6 - Final Assembly
Setting up the Wah Pot with the Rack
With the wah pedal still upside down, push the wah
base to close against the treadle so that the footswitch
is lightly resting against the treadle in toe-down position.
While looking at the top of the wah pot from the input jack side of the enclosure, use your fingers
to rotate the pot's shaft and gear to the full counter-clockwise position.
(If you measure the electrical resistance between pot lugs 1 and 2 with an ohm meter at this setting,
you should be measuring the pot's minimum resistance - i.e. close to 0Ωinstead of 100kΩ).
Now, bring the rack forward so that its teeth interlock with those of the pot's gear. (You may
have to advance the pot's shaft slightly clockwise to get a snug fit between the rack teeth and pot
gear).
Loosen the rack tensioner screw and push the rack
tensioner to the side so that the wah pot's gear is
completely separated from the rack.
1
2
Rack
Tensioner
While holding the rack against the pot gear, bring the rack tensioner so that its edge is parallel
with the ledge in the rectangular opening as shown in the drawing.
While holding the rack against the pot gear, position the rack
tensioner so that its edge stays parallel with the edge of the
rectangular opening as shown in the drawing. Pull the rack
tensioner towards the rack as much as possible and hold it there
while using a screw driver to tighten the rack tensioners screw
all the way down. Make sure the front edge of the tensioner is
still parallel. (You can add a dab of Vaseline to the junction
between the rack and the rack tensioner for lubrication).

TIP LUG
TIP
LUG
GROUND
LUG
1
2
3
4
5
7
89
10
11
12
14
15
16
103K
400V
1.5K
103K
400V
470K
470K
1K
10K
22K
270
.22µ
E
B
C
MPS
A18
Q2
MPS
A18
E
B
C
Q1
1"
13
Installing the Foam Battery Cushion
Locate the remaining piece of double sided foam tape and the gray foam battery cushion. This
will be installed to keep the battery in place.
Remove the backing from one side of the foam tape and attach to the inside of the wah base at
the heel end roughly centered about 1" away from the rear edge as shown by the rectangle in
the drawing below.
Remove the remaining backing of the foam tape and place the foam block over the tape so the
angled corners just clear the screw holes. Press down on the middle of the foam block to make
sure it is firmly secured to the base.
Install a fresh 9 volt battery and lay it over the gray foam block. Place the bottom cover over the
base and attach the base using the feet and their mounting screws.
Fixing a Squeaky Wah
If you find that your wah pedal is squeaking when you rock the
treadle, try squirting WD40 into the four junctions where the
bearing pin meets the bearing pin mounts.
Adjustment of the Footswitch Height
If you find that the footswitch engages too easily while rocking the treadle back and forth with
your foot, you can lower the height of the footswitch by swapping the location of the large nylon
washer and the lock washer.
If you find that the footswitch does not engage when pressing the toe-end of the treadle all the
way down with your foot for bypass mode, you can raise the height of the footswitch by removing
the lock washer from the switch altogether.
Wah Base
Nylon Washer
Hex Nut
Outside
Inside
Wah Base
Lock Washer
Nylon Washer
Hex Nut
Outside
Inside
Wah Base
Lock Washer
Nylon Washer
Hex Nut
Outside
Inside
Lower Raise
BASE
OUTER
SURFACE
Mount Mount
Four Junctions

Output Jack
Input Jack
DRAWING 1
RING LUG
TIP LUG
DC Power
Jack
GROUND LUG
TIP
LUG
GROUND
LUG
INSIDE VIEW OF THE BASE ENCLOSURE
14

Output Jack
Input Jack
DRAWING 2
RING LUG
TIP LUG
DC Power
Jack
GROUND LUG
TIP
LUG
GROUND
LUG
INSIDE VIEW OF THE BASE ENCLOSURE
1
2
3
4
5
6
1
2
3
17 18 20 21
22
23
1
2
3
4
5
6
7
8
19
9
10
11
12
13
14
15
16
15

Output Jack
Input Jack
DRAWING 3
RING LUG
TIP LUG
DC Power
Jack
GROUND LUG
TIP
LUG
GROUND
LUG
INSIDE VIEW OF THE BASE ENCLOSURE
1
2
3
4
5
6
1
2
3
17 18
20 21
22
23
1
2
3
4
5
7
8
19
9
10
11
12
14
15
16
.22µ
33K
4.7µF35V
68K
103K
400V
1.5K
103K
400V
470K
470K
1K
10K
22K
270
.22µ
E
B
C
2N
5088
Q2
2N
5088
E
B
C
Q1
Black
Red
100K
16