Epiphone Baby Will Manual

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“Baby Will” Valve unior Conversion Version 4
Build Manual 22 September 2009
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“Baby Will”
Valve Junior Conversion
Build Manual

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“Baby Will” Valve unior Conversion Version 4
Build Manual 22 September 2009
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1. Introduction
This manual contains instructions to convert an Epiphone Valve Junior guitar
amplifier to a roaring 18Watt amp modeled after the famed Marshall 1974X
circuit The heart of it all is the “Baby Will”, a simplified version of Marshall’s
1974X amp known as the LiteIIb The Baby Will takes the LiteIIb circuit and
conveniently lays it out in a printed circuit board, PCB, package
This manual provides instruction for the assembly of version 2 3 of the Baby Will
circuit board Several of the pictures or diagrams in this manual may refer to or
display a previous version of the circuit board However, these still apply to the
current version
To simplify things,
• The Epiphone Valve Junior will be referred to as EVJ, and
• The “Baby Will” 18 Watt LiteIIb PCB will be referred to as the Baby Will
This manual guides you through the conversion which includes:
• removing the stock EVJ chassis from its cabinet,
• extracting the stock EVJ pcb,
• assembling the Baby Will,
• installation and hookup of the Baby Will into the EVJ chassis,
• initial power-up and testing, and
• reinstalling the chassis back into the EVJ cabinet to finish up the job

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Here’s a look at the Baby Will PCB if you haven’t purchased yours yet
Version 2 3

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2. Electrical Shock Warning
Building tube amplifiers involves working with, or around, high voltages Working
inside a tube amplifier can be dangerous if you don't know the basic safety
practices Building, modifying, or repairing tube amplifiers should only be
performed by trained personnel
3. Disclaimer of Liability
GuitarAmplifierPCBs com assumes no liability or responsibility, under any
circumstance, for personal injury or damage to property or personal property
GuitarAmplifierPCBs com reserves the right to make design changes or
improvements without obligation to revise prior versions
All specifications are subject to change without notice

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Table of ontents
1 Introduction 2
2 Electrical Shock Warning 4
3 Disclaimer of Liability 4
4 Project Overview 6
4 1 Here’s what you’ll need: 6
4 1 1 Parts: 6
4 1 2 Tools: 6
4 1 3 Supplies: 6
5 Let’s get started… 7
5 1 Remove the EVJ chassis 7
5 2 Remove the EVJ’s Stock Components 8
5 2 1 Remove the Tubes and Tube Retainers 8
5 2 2 Remove the Output Transformer 8
5 2 3 Clean Up the Power Transformer 10
5 2 4 Remove the Volume Potentiometer 11
5 2 5 Remove the Stock EVJ Circuit Board 11
6 Prepare the Chassis 13
6 1 Layout and Drill 13
6 1 1 Layout the Drill Plans 13
6 1 2 Drilling the Chassis 14
7 The Baby Will 16
7 1 Assemble the Baby Will Circuit Board 16
7 1 1 Tube Sockets 16
7 1 2 PCB Standoffs 17
7 1 3 The Power Grid 17
7 1 4 Signal Path and Cathode Resistors 19
7 1 5 Sag Resistor 19
7 1 6 Signal Path and Cathode Capacitors 20
7 1 7 Hum Balance 20
7 1 8 Filter Capacitors and Ground Wire 21
7 1 9 Jumper Wires 21
7 1 10 Input Jack Hookup 22
7 1 11 Volume and Tone Controls 25
8 Putting it All Together 26
8 1 Install the New Components 26
8 1 1 The New Output Transformer 26
8 1 2 The Baby Will PCB and Tube Hardware 28
8 1 3 Hookup the Leads to the Baby Will 29
9 Turn on the Power 31
9 1 Check Your Work 31
9 1 1 Take a Break 31
9 1 2 Visual Inspection 31
9 2 Power Up without Tubes 32
9 2 1 The First Power Up 32
9 3 Power Up with Tubes 33
9 3 Power Up with Tubes 34
9 3 1 The Real Test 34
11 Finish Things Up 35
11 Finish Things Up 36
11 1 Re-Assemble the Amp 36

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4. Project Overview
You’ll find that this is a fun project that can be completed by an inexperienced
builder in a day or two We at GuitarAmplifierPCBs com wrote this manual
specifically for the novice builder So anyone can do it Really, it’s simple and it
doesn’t require expensive tools or complex equipment
4.1 Here’s what you’ll need:
4.1.1 Parts:
• The “Baby Will” circuit board
• Misc parts and components (refer to the VJ Conversion parts list
document for a full listing of what parts are needed and where you
can buy them)
4.1.2 Tools:
• Phillips head screw driver
• Standard screw driver
• Needle nose pliers
• Adjustable wrench
• Power drill (corded or cordless)
• 1/8, 5/15, 3/8 in Metal cutting drill bits
• Unibit or punch (you’ll need something to make two 7/8 in holes)
• Soldering iron (15-40 watt power rating)
4.1.3 Supplies:
• Fluxed solder
• Roughly 3 ft 600v rated wire (22-18 AWG)
• ¼” – 32 Spade connectors (you’ll need at least three)
• Tag strip

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5. Let’s get started…
OK So you have all the parts and are ready to start Let’s get that EVJ chassis
out of the cabinet
5.1 Remove the EVJ chassis
Take off the back panel by removing the seven (7)
screws using a Phillips head screw driver
Be careful pulling off the back panel
They are typically stuck onto the chassis
Slowly pull from each side to prevent the
tolex from lifting off the panel
Locate the screw caps on the top of the EVJ Using
a standard screw driver, the smaller the better, pry
up the caps until you can pull them out of their
sockets
Remove the four chassis screws and pull out the
chassis

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5.2 Remove the EVJ’s Stock omponents
A few of the stock EVJ parts have to be replaced The tubes, tube retainers,
stock circuit board, and output transformer need to be removed
5.2.1 Remove the Tubes and Tube Retainers
It’s as simple as:
• lift the tube retainer off the power tube,
• turn the retainer shield until the spring lifts the shield off the per-amp tube,
• pull the tubes out, and
• unclip the power tube retainer
These items can be discarded They will not be used later in the build
Now that the tubes and their hardware have been
removed we can take a look inside This is a version 2
EVJ You can tell by the green board and the rectified
DC heater supply Version 3s have a black board
5.2.2 Remove the Output Transformer
To remove the output transformer,
disconnect its wire leads from the main
amp circuit board and the output jack
circuit board
You don’t need to label the
leads since this output
transformer won’t be used
later in the build However,
it’s recommended to label
them just in case you want
to use it in another build at a
later time
Pull these two spade connectors from the main circuit board

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Unscrew the output jacks from the chassis and
separate the board from the chassis
The board will be glued to the chassis It
may require some extra work to pick the
glue off Be careful not to damage the
board or the output jacks They will be
reused later
Flow the solder to each transformer
lead on the output jack board and pull
the lead out
Remove the fastening nut at the star
grounding post and remove the output
board’s ground wire
Clean up any remaining solder off the
board to assist in the installation of the
new transformer later in the build
Now that all of the leads are free,
remove the mounting screws to
separate the transformer from the
chassis

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Here’s the output board and the output transformer
after removal Set the output board aside It will be
used later in the build
The output transformer can be discarded It will
NOT be used later in the build
5.2.3 lean Up the Power Transformer
The stock EVJ’s power transformer provides leads for various mains supply
voltages The extra leads are fastened to dead posts on the stock circuit board
for storage We are going to clean up the inside of the chassis by pulling any
unused power transformer leads outside of the chassis cavity
Disconnect these three (3) leads from
the stock EVJ circuit board
Version 1 and 2 EVJ will
have 12v secondary taps
tied off and tucked inside the
chassis These need to be
pulled outside and secured
as well
After the leads are all pulled outside
the chassis, bundle them together and
tie them off

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5.2.4 Remove the Volume Potentiometer
Unscrew the fastening nut from the volume
potentiometer
Pull the volume pot back into the chassis Leave it
connected to the stock EVJ circuit board
The volume pot will be glued to the
chassis This part will NOT be used later
in the build, so use whatever force you
need
5.2.5 Remove the Stock EVJ ircuit Board
Disconnect these four (4) leads from
the stock EVJ circuit board
Lift the ground wire from the star
ground post
Unplug the input jack wire at the circuit
board
Remove the six (6) screws fastening
the circuit board to the chassis

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Remove the stock circuit board and
pull all of the power transformer leads
to the rim of the chassis
Salvage the ground wire from the
stock circuit board for use later
Unscrew the input jack and remove it
from the chassis Set it aside for use
later

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6. Prepare the hassis
6.1 Layout and Drill
The Baby Will circuit board, tone potentiometer, and the new output transformer
require some drilling in the chassis
6.1.1 Layout the Drill Plans
Always verify you are using the latest version of the drill plan posted on
GuitarAmplifierPCBs com
If you can not print onto 11x17” paper, you can take an electronic
version of the drill plan to Kinkos They will print it professionally for
under $1
Print out a copy of the VJ Conversion Drill Plan Make sure it is printed to scale
Cut away the unused
portion of the drill plan as
shown
Align the drill plan to the
chassis using the
alignment holes
indicated on the plan
Affix the plan to the
chassis with a generous
amount of tape or
Elmer’s white glue

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6.1.2 Drilling the hassis
Start by setting the center of each hole to be drilled A center punch is often
used Here, a 1/16” drill
bit was used as shown in
the picture
Use the appropriate drill
bit size as prescribed by
the drill plan
Here, a unibit was used to drill out the 7/8” hole for the two (2) additional tube
socket holes
Deburr or countersink
each hole to ensure no
sharp edges will cause
injury or component
failure

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Version 2 3 of the Baby Will circuit board was designed to use most of the stock
chassis mounted pcb standoffs However, you need to remove one (1) standoff
for the board to fit
Drill out and remove the stock standoff as shown in the picture below

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7. The Baby Will
7.1 Assemble the Baby Will ircuit Board
The anticipation has been killing you, hasn’t it? Finally, the assembly of the Baby
Will begins
Did you check you make sure you have all of the
parts you’ll need to complete the assembly?
I wish I did
7.1.1 Tube Sockets
The tube sockets get installed on
the back side of the board
I repeat the back side of the
board
Insert the tube sockets as shown
They only go in one way (on the
back side)
Flip the board over and rest the sockets against your work bench/table A piece
of cardboard is useful to hold the sockets in place when flipping the board over
Slip the cardboard away when it’s resting on the bench Check to make sure
each socket is properly seated Then solder each leg of the sockets The holes
are through plated so the solder will flow into the hole and through to the other
side of the socket leg creating a very durable connection

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7.1.2 P B Standoffs
Install the one (1) PCB standoff on the back
side of the board in the location shown
7.1.3 The Power Grid
Install the four (4) rectifier diodes
Orient the diodes as indicated on the
circuit board Bend the leads over,
insert them into the board, and bend
them to the side as shown Solder
them to the board

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Trim the leads off at the top of each
solder pool
Install, solder and trim all of the resistors in the power grid as shown Refer to
the latest version of the schematic on GuitarAmplifierPCBs com, the Baby Will
circuit board, and the component package to identify, locate and position
component values
The filtering capacitors are not installed at this time The height of these
capacitors interferes with the installation of the other components These
capacitors will be the last component installed

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7.1.4 Signal Path and athode Resistors
Install, solder and trim all of the signal path and cathode resistors as shown
Don’t bother with the input section We’ll get to that later
7.1.5 Sag Resistor
Install, solder and trim the sag resistor as shown

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7.1.6 Signal Path and athode apacitors
Install, solder and trim all of the signal path and cathode capacitors as shown
Make sure the 47uF cathode bypass capacitors are oriented with the polarities
indicated on the circuit board
7.1.7 Hum Balance
Version 2 3 of the Baby Will circuit board is equipped with a DC elevated artificial
center tap It uses two (2) 100 ohm 1% resistors to tie each lead of the tube
heater supply to the cathodes of the power tubes, which operate at around
10Vdc This creates the DC elevated artificial center tap, which is a very
effective method for reducing audible hum in the amp
Install, solder and trim the two (2) 100 ohm 1% resistors as shown below