Mod THE PERSUADER User manual

1Copyright © 2014 by modkitsdiy.com
Use these instructions to learn:
How to build a tube preamp pedal
The Persuader uses a gain boost circuit driving a 12AX7 preamp tube operating in starved plate mode to go
from clean, warm tone to smooth, real tube overdrive.
THE PERSUADER (K-930)
Signal Input
(From Guitar)
Unplug when not in use
to save battery life.
9 VDC
CENTER (-)
ADAPTER
Signal Output
(To Amplifier)
Warning: This circuit was designed for use with a 9 VDC power supply only.

TABLE OF CONTENTS
TOOL LIST …………………………………………………………………………...2
PARTS LIST DRAWINGS………………………………………………………….3, 4
FINAL ASSEMBLY REFERENCE DRAWING………………………………………5
SOLDERING TIPS …………………………………………………………………...6
STEP BY STEP ASSEMBLY INSTRUCTIONS ………………………………7 - 12
Section 1 – Mount ¼” Jacks and Terminal Strip Components ……...………...7
Section 2 – Mount the Potentiometer, Footswitch and DC Power Jack …..…...8
Section 3 – Connect the 5KL Potentiometer …………………………………...9
Section 4 – Mount the Tube Socket, Shield and 5 Lug Terminal Strips ……...9
Section 5 – Connect the DC Power Components ……………………………10
Section 6 – Wiring Connections in the Vacuum Tube Section ……..……….10
Section 7 – Mounting Components in the Vacuum Tube Section …………….11
Section 8 – Wire the Output Jack and Footswitch Connections .…………….12
Section 9 – Finishing Up ………………………………………………………12
ASSEMBLY DRAWINGS (9 Drawings) ………………………………13 – 17
These are the last 5 pages. They should be separated and used as a reference to help
assemble the kit correctly.
2
TOOL LIST
Wire Strippers
Needle Nose Pliers
Cutting Pliers
Desoldering Pump
Solder (60/40 rosin core)
Soldering Station
Phillips Head Screwdrivers
Slotted tip screwdrivers (3 mm tip)
Channellock Pliers (or similar type)
Ruler
Hobby Vise (or other means to secure box while working)

Enclosure
P-H1590BBCE-P (1)
Round Black Knob
P-K325 (2)
Battery Clip
S-H155 (1)
¼” Mono Jack (Output Jack)
W-SC-11-T (1)
¼” Stereo Jack (Input Jack)
W-SC-12B (1)
DPDT Foot Switch
P-H498 (1)
Preamp Tube (Dual Triode, High Mu)
T-12AX7-S-JJ (1)
Potentiometers: 250KA and 5KL
R-V38-250KA (1)
Terminal Strips with 5 Terminals
P-0501H01 (1)
Terminal Strip with 8 Terminals
P-0802H (1)
#6 Screws (3/8" long)
S-HS632-38 (4)
#6 Nuts
S-HHN632 (4)
Stranded Wire (22 AWG) - Blue
K-PUL1569-BLUE (5 FT)
PARTS LIST 1
3
RING LUG
GROUND LUG
TIP LUG
GROUND LUG
TIP LUG
1
2
3
BOTTOM VIEW OF
BASE PIN
ORIENTATION
1
2
4
3
5
6
7
8
9
R-V38-5KL (1)
P-0501H05 (1)
1st Lug Common
5th Lug Common
COM
1 2 3 4 5
COM
1 2 3 4 5
1 2 3 49

PARTS LIST 2
4
C-PFD1-50-R (2)
0.1µF Capacitor
104K
C-PFD047-50-R (1)
0.047µF Capacitor
473K
DC Power Jack
S-H750 (1)
10µF 50V
C-ET10-50 (1)
10µF Polarized Capacitor 50V
#4 Screws (3/8" long)
S-HS440-38 (2)
#4 Nuts
S-HHN440 (2)
P-Q1N4005 (2)
Diode (solid state) 1N4005
220µF 50V
C-ET220-50 (2)
220µF Polarized Capacitor 50V
R-A33K (1)
33kΩ Resistor ½ W
orange
orange
orange
gold
33K
brown
black
green
gold
1M
R-A1M (3)
1MΩ Resistor ½ W
R-A5D1K (1)
5.1KΩ Resistor ½ W
green
brown
red
gold
5.1K
R-A68K (1)
68KΩ Resistor ½ W
blue
gray
orange
gold
68K
1
2
3
456
7
8
9
Tube Socket and Shield
P-ST9-300 (1) P-SS9-325-Y (1)
R-A15K (1)
15KΩ Resistor ½ W
brown
green
orange
gold
15K
R-A4D7K (1)
4.7KΩ Resistor ½ W
yellow
violet
red
gold
4.7K
brown
black
red
gold
1K
R-A1K (1)
1KΩ Resistor ½ W
P-QBS170 (1)
N-Channel MOSFET (BS170)
BS170
Caution: MOSFETs can easily be
damaged by static electricity. Handle
with care.

104K
BS170
1M 1M
5.1K
10µF 50V
220µF 50V
5KL
250KA
1
2
3
4
56
7
8
9
220µF 50V
2
68K
4.7K
1K
1M
104K
473K
33K
15K
3
FINAL ASSEMBLY REFERENCE DRAWING
This is a large version of the final assembly drawing. Refer to this drawing as you make your way through each step of the instructions. Before you make a new
connection at a particular terminal or solder lug, notice how many other connections will be made at that terminal. That way you can decide whether it’s best for
you to solder the connection and leave space open for future connections or hold off on soldering until after every connection at that location has been made.
5
4
1
6
5
23

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.

SECTION 1 – Mount ¼” Jacks and Terminal Strip Componets
Please refer to DRAWING 1 and DRAWING 2.
Orient box with two 3/8" holes on top and ½” hole nearest you.
Mount input jack in 3/8" hole on left side of box with hardware provided.
Washer goes under nut on outside of box. Make sure center solder lug
of input jack is facing up. Correct positioning of jack will make soldering
connections much easier. When positioned correctly, tighten nut.
Mount output jack in 3/8" hole on right side of box with hardware
provided. Washer goes under nut on outside of box. Make sure two
solder lugs are in most upright position before tightening nut.
Mount the 8 lug terminal strip to the two 9/64" holes as shown in drawing
2 using #6 hardware. We will refer to terminal numbers as illustrated
below when connecting components.
input
jack
output
jack
1 2 3 4 5 6 7 8
GROUND LUG
TIP LUG
Output Jack
RING LUG
GROUND LUG
TIP LUG
Input Jack
Terminal #3 will have six components connected to it. Because of this
we will use both the upper and lower portion of the terminal.
lower holes
31 5
Terminals #1 & 3:
“Anode” to terminal #1
“Cathode” to terminal #3
1) Mount the diodes to the lower set of holes, but do not solder.
Terminals #3 & 5:
“Anode” to terminal #3
“Cathode” to terminal #5
cathodeanode
cathode side is
marked with a
silver band
2) Mount one end of a .1µF capacitor to the lower
hole of terminal #3. Now solder the lower set of
holes at terminals #1, 3, and 5.
7
Connect and solder all of the following to their respective terminals as listed. (Make sure none of
the component leads are so close together that it could lead to an unintended connection). Be
careful not to overheat the solid state devices (diodes and transistor) when soldering.
1 5
3
104K
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 prevents the stranded wire from
fraying and makes soldering much easier.
Note: The other end of the .1 µF capacitor will be connected on p. 11 of these instructions.

104K
Terminals #1 & 3:
mount one of the 1M resistors to 1 & 3.
4) Mount the 1M resistors.
Terminals #3 & 4:
mount the other 1M resistor to 3 & 4.
Terminals #5 & 6:
5) Mount the 5.1K resistor.
Terminals #4 & 6:
6) Mount a 2" jumper wire.
Terminals #6 & 7:
7) Mount the 10µF capacitor.
mount the positive end to terminal 6.
mount the negative end to terminal 7.
Terminals #5 & 8:
8) Mount a 220µF capacitor.
10µF 50V
Positive
End
8
Terminals #2, 3 & 4:
“Source” to terminal #2
“Gate” to terminal #3
“Drain” to terminal #4
BS170
DSG
3) Mount the BS170 MOSFET.
BS170
D
SG
The remaining components and wires can be connected to the upper portion of their respective
terminals. Unless otherwise noted, “mount” means to mount the component, solder the component in
place and trim the leads.
mount the positive end to terminal 5.
mount the negative end to terminal 8.
220µF 50V
Mount footswitch in ½” hole. Large nylon washer
goes under mounting nut on outside of box. Lock
washer mounts on inside of box between the box
surface and the other nut. Make sure that the
footswitch solder lugs are oriented left to right, not
up and down as illustrated here.
SECTION 2 – Mount the Potentiometer, Footswitch and DC Power Jack
104K
BS170
DS G
1M 1M
5.1K
10µF 50V
1 85
220µF 50V
Please refer to DRAWING 3.
Mount the 5K potentiometer in the upper left hole using hardware provided. Mount the 250K
potentiometer in the upper right hole using the hardware provided. Solder lugs for both pots should
be pointed toward the bottom side of the enclosure. (Remove the small mounting tab on each pot
by bending it back with pliers and clipping it off with cutters).
Incorrect OrientationCorrect Orientation
This component
is delicate, be
careful not to
burn it or break
off the leads by
bending them
repeatedly.
Caution: MOSFETs can easily be damaged by static electricity. Handle with care.
input
jack
output
jack
1 3
64
2
5

Mount power adapter jack in 15/32” hole on bottom left side of box. Orient solder lugs on power
adapter jack so larger center-pin lug is facing the bottom side of box. Tighten adapter jack.
CENTER-PIN LUG
POSITIVE-SWITCH LUG
POSITIVE LUG
Power
Adapter Jack
SECTION 3 – Connect the 5KL Potentiometer
Please refer to DRAWING 3.
1
2
3
GROUND
LUG
5KL
Cut a 2” length of wire, strip ½” of insulation off of one end and
tin. Use this one end to connect the 5K pot lug #2 with lug #3.
Connect the other end of the wire to the ground lug of the input
jack. ½” stripped end
connects both 2
and 3 together.
Cut a 3" length of wire and connect the 5K pot lug #1 to the terminal
strip terminal #2.
SECTION 4 – Mount the Tube Socket, Shield and 5 Lug Terminal Strips
Please refer to DRAWING 4.
1
2
3
456
7
8
9
1) From outside of the enclosure, insert the two #4 screws through the
mounting holes of the tube shield base and into the two 1/8" chassis holes.
ENCLOSURE BOUNDARY
Use the #4 screws and nuts to mount the tube socket and shield as shown below.
Mount the socket with the large gap
between pins 1 and 9 on the side of the
enclosure closest to the footswitch.
2) Place the tube socket onto the two screws so that the gap between pins 1
and 9 is directed toward the end of the box with the footswitch.
OUTSIDE OF THE ENCLOSURE
INSIDE OF THE ENCLOSURE
9
1
2
4
3
56
7
8
9
Note: Due to variance in socket manufacturing, the pins on your socket may not be in the same position relative to the
socket's mounting holes as shown in the layout drawings; however, the gap in the socket will always be between pins 1
and 9. Make sure you are making your tube socket connections to the correct pin numbers with respect to the gap and
not their position relative to the mounting holes.
1
2
34 5
6
7
8
9
1
2
3
456
7
8
9
Socket
Mounting
Holes
Socket
Mounting
Holes
Gap between
pins 1 and 9.
Bottom view of a
12AX7 base pin
orientation.

10
SECTION 5 – Connect the DC Power Components
Please refer to DRAWING 5 and DRAWING 6.
Locate the battery snap connector. Connect
and solder the red lead to the positive-switch
lug of the power adapter jack.
RING LUG
GROUND LUG
TIP LUG
Input Jack
Connect and solder the black lead to ring lug on the input jack.
CENTER-PIN LUG
POSITIVE-SWITCH LUG
POSITIVE LUG
Power Adapter Jack
Connect the positive lead of the remaining 220 µF capacitor to the
positive lug on the adapter jack (do not solder here, yet). Connect
the negative lead of this cap to terminal #1. Positive
End 220µF 50V
Cut a 4 ½” length of wire. Strip ¼” insulation from each end. Wrap one end around the positive lug of
the adapter jack (same terminal as the 220µF capacitor). Now solder this connection and make sure
the positive capacitor lead and wire end are not touching the nearby adapter jack lugs.
Connect the other end of this 4 ½” wire to the lower hole terminal #17.
SECTION 6 – Wiring Connections in the Vacuum Tube Section
Terminals #5 & #12
1) Strip and tin a 2" piece of wire and connect:
Suggestion: Connect to the lower hole of terminal #12 to make it easier when connecting other components to this
same terminal later in the instructions.
Please refer to DRAWING 7.
Cut a 2 ½” length of wire and connect the adapter jack center-pin lug to terminal #1.
Terminals #1 & #9
2) Strip and tin a 3 ½" piece of wire and connect:
Suggestion: Connect to the lower hole of terminal #9 and route the wire along a path so that its insulation also serves
as a spacer between the terminal strip and the 5K potentiometer body.
3) Fasten the two #4 nuts onto the two screws and tighten.
COM
1 2 3 4 5
COM
1 2 3 4 5
4) Mount the 5 lug terminal strip with the
grounded terminal #1 between the 5K pot and
the tube socket using #6 hardware.
5) Mount the 5 lug terminal strip with the
grounded terminal #5 between the 250K pot and
the tube socket using #6 hardware.
Be careful to mount these so that none of the terminals are
unintentionally shorted to ground from touching the
potentiometer bodies or the tube socket mounting ring.

Tube Pin #5 & Terminal #17
5) Strip and tin a 3 ½" piece of wire and connect:
Suggestion: Route the wire along a path to terminal #17 so that its insulation also serves as a spacer between the
terminal strip and the 250K potentiometer.
11
Tube Pin #6 & Terminal #14
6) Strip and tin a 1" piece of wire and connect:
7) Strip and tin a 1 ½" piece of wire and connect:
Terminal #15 & 250K pot lug #1
1
2
3
250KA
8) Strip and tin a 1 ½" piece of wire and connect:
Terminal #11 & Terminal #13
9) Strip and tin a 1 ¾" piece of wire and connect:
Terminal #12 & Terminal #16
10) Strip and tin a 4" piece of wire and connect:
Terminal #7 & Terminal #10
SECTION 7 – Mounting Components in the Vacuum Tube Section
Please refer to DRAWING 8.
Terminals #5 & #17
1) Mount the 1K resistor to:
Terminals #16 & Tube pin #7 (Do not solder the connection at pin #7, yet.)
2) Mount the 1M resistor to:
Tube pin #1 & Tube pin #7 (Now solder the connection at pin #7.)
3) Mount the 0.1 µF capacitor to:
Tube Pins #3 & #8 to Terminal #13
3) Cut a 3" piece of wire. Strip ¾” of insulation from one end and tin. Strip ¼” of insulation from the
other end and tin. Connect:
Use the ¾” end to connect both tube pins #3 and #8.
Suggestion: Route the wire along a path to terminal #13 so that its insulation also serves as a spacer between the
terminal strip and the tube socket.
Tube Pin #4 & Terminal #9
4) Cut a 1" piece of wire and connect:

SECTION 8 – Wire the Output Jack and Footswitch Connections
Please refer to DRAWING 9.
250K Pot lug #3 & Output Jack ground lug
1) Strip and tin a 1" piece of wire and connect:
12
GROUND LUG
TIP LUG
Output Jack
2) Connect the free end of the 0.1 µF cap from Terminal #3 to Footswitch lug #3
RING LUG
GROUND LUG
TIP LUG
Input Jack
Input Jack tip lug & Footswitch lug #2
3) Strip and tin a 2 ½” piece of wire and connect:
250K Pot lug #2 & Footswitch lug #6
4) Strip and tin a 4 ½” piece of wire and connect:
Footswitch lug #1 & Footswitch lug #4
5) Strip and tin a 1 ½” piece of wire and connect:
Output Jack tip lug & Footswitch lug #5
6) Strip and tin a 3 ½” piece of wire and connect:
SECTION 9 – Finishing Up
Attach the knobs provided to the two potentiometer shafts. Install 9 volt battery, close cover using
screws provided. Plug guitar into input jack on right. This turns unit on. Plug cable into output jack
and plug into your amplifier. Battery will last only about 1 hour of continuous operation. 9 volt,
center negative power supply is highly recommended for use with this unit.
Unplug from the input jack of the unit to turn it off and save power.
It’s always a good idea to thoroughly double-check your connections before applying power.
Terminals #14 & #15
5) Mount the 0.047 µF capacitor to:
Terminal #10 & Tube pin #2 (Do not solder the connection at pin #2, yet.)
6) Mount the 15K resistor to:
Terminal #11 & Tube pin #2 (Now solder the connection at pin #2.)
7) Mount the 4.7K resistor to:
Terminal #12 & Tube pin #1
8) Mount the 68K resistor to:
Terminal #16 & Tube pin #6
4) Mount the 33K resistor to:
Footswitch lug numbering convention
input
jack
output
jack
1 3
64
2
5

Output Jack
Input Jack
DRAWING 1
DRAWING 2
RIGHT SIDE
LEFT SIDE
TOP
BOTTOM
INSIDE VIEW OF THE ENCLOSURE
3/8"
½”
3/8"
3/8" 3/8"
9/64"
104K
BS170
DS G
1M 1M
5.1K
10µF 50V
1 85
220µF 50V
1/8"
3/4"
1/8"
13

104K
DRAWING 3
DRAWING 4
Output Jack
Input Jack
BS170
DS G
1M 1M
5.1K
10µF 50V
1 85
220µF 50V
1
2
31
2
3
5KL 250KA
104K
BS170
DS G
1M 1M
5.1K
10µF 50V
1 85
220µF 50V
1
2
31
2
3
5KL 250KA
1
2
3
456
7
8
9
1/8"
1/8"
14

DRAWING 5
DRAWING 6
104K
BS170
1M 1M
5.1K
10µF 50V
1
220µF 50V
5KL 250KA
1
2
3
456
7
8
9
When the instructions mention a terminal #__, this drawing illustrates
the terminal numbering convention used for all three terminal strips.
Terminal Numbering Convention
1 8
5
1
2
3
456
7
8
9
9
13
14
18
2 3 46 7
10
11
12
15
16
17
5KL 250KA
RED
BLACK
220µF 50V
17 Output Jack
Input Jack
15

DRAWING 7
104K
BS170
1M 1M
5.1K
10µF 50V
5
220µF 50V
5KL 250KA
1
2
3
456
7
8
9
220µF 50V
13
1
9
18
14
1
DRAWING 8
5
1
2
3
4
56
7
8
9
14
10
11
12
15
16
17
68K
4.7K
1K
1M
104K
473K
33K
15K
16

DRAWING 9
104K
BS170
1M 1M
5.1K
10µF 50V
220µF 50V
5KL 250KA
1
2
3
456
7
8
9
220µF 50V
2
68K
4.7K
1K
1M
104K
473K
33K
15K
3
Output Jack
Input Jack
17
1
4 65
2 3

Use this troubleshooting supplement to help:
Measure DC voltage test points to identify major discrepancies and locate problem areas.
(Keep in mind that the voltage measurements will vary slightly from kit to kit. The voltages you measure should be in
the same ballpark, but do not expect to get the exact same value.)
A
B
C
D
E
F
G
H
I
Test Point
Positive power supply voltage
Terminal #5
Tube pin 1 (plate)
Tube pin 6 (plate)
Tube pin 2 (grid)
Tube pin 7 (grid)
MOSFET “Source” lead
MOSFET “Gate” lead
MOSFET “Drain” lead
Location Description Controls turned to minimum Controls turned to Maximum
9.2 VDC 9.2 VDC
8.8 VDC 8.3 VDC
8.3 VDC 7.8 VDC
7.0 VDC 6.7 VDC
0 VDC 0 VDC
0 VDC 0 VDC
1.6 VDC 0 VDC
3.4 VDC 1.9 VDC
7.1 VDC 4.0 VDC
Using a volt meter, connect the ground side lead of the meter to any ground point on the pedal.
One ground point would be the output jack’s ground lug. The other volt meter lead will be used to
measure DC voltage at the test points listed above and shown in the drawing on the next page.
First, plug a guitar cable into the input jack and take measurements at each test point with both
controls turned all the way down taking note of each measurement. Next, take measurements at
each test point with both controls turned all the way up and take note of each measurement. Any
major differences between the voltages listed above should indicate a problem area.
1
5
1

104K
BS170
1M 1M
5.1K
10µF 50V
220µF 50V
5KL
250KA
1
2
3
4
56
7
8
9
220µF 50V
68K
4.7K
1K
1M
104K
473K
33K
15K
1
465
2
A
B
C
DE F
G
H
I
GROUND
DC Voltage Test Points
Guitar cable must be
plugged into the input
jack while taking voltage
measurements

104K
BS170
1M 1M
5.1K
10µF 50V
220µF 50V
5KL 250KA
1
2
3
4
56
7
8
9
220µF 50V
68K
4.7K
1K
1M
104K
473K
33K
15K
1
465
2
GROUND
Guitar cable must be
plugged into the input
jack while taking voltage
measurements
AC Voltage (Signal) Test Points
1
2
2
5
8
10
11
12
Turn all the
way up
Turn all the
way up
9
7
4
3
3
6
Connect your guitar to the input jack and take AC voltage measurements at each test point with
both controls turned all the way up. At each test point the AC voltage should increase dramatically
each time you strum the guitar. (No strum = 0.0 VAC, Hard strum = anywhere from 10 mV to 2 V).
Make sure
the pedal is
not in bypass
mode.