Mojotone British 100 Watt Style Amp Kit Manual 2012 Page 1

Mojotone British 100 Watt Style

Amp Kit Instruction Manual

Tools needed for build: 40 W Soldering Iron

Wire Cutters / Stripper

Needle Nose Pliers

Phillips Head Screwdriver

Small Flat Head Screwdriver

AC/DC Multimeter with Resistance Reading

44 Rosin Core Solder

Lay out parts for a quick inventory (Photo 1) Compare physical inventory to the included bill of materials. Packaging mistakes are rare for Mojo but

double check us before you start your build.

Install chassis mounted hardware Tube Sockets - Install so that they all face the same direction (noting pin #1 orientation)

Power Transformer - Make sure to mount the PT so that the label faces toward tube sockets. This will be

helpful for anyone looking at the transformer model number without having to take the chassis out of the

amp.

Output Transformer - Feed wires through grommets and note wire locations.

Install Potentiometers.

Install Bias Potentiometer.

Install Input, Output Jacks, and Switches.

Fuse Holder - Install fuse at same time so you wont forget.

Pilot Light Assembly

Photo 1 - Lay out parts for quick inventory

Mojotone British 100 Watt Style Amp Kit Manual 2012 Page 2

Photo 2 - Installing Chassis Mounted Hardware

Photo 3 - Filter Caps

Photo 4 - Pots & Faceplates Installed

Mojotone British 100 Watt Style Amp Kit Manual 2012 Page 3

Turretboard Assembly

Tech Tip - Always use a clean tip on your soldering iron to make positive, clean solder joints, (cold

solder joints can be a major problem in hand-wired amps)

Always try to rely more on the schematic than the wiring diagram in any circuit.

Be sure of component placement and orientation, especially capacitors (positive, negative)

Make sure that the white dot on the optoisolator is pointing in the direction of the tubes.

It is recommended to place the components on the turretboard and the wire leads before soldering.

This step can help prevent cold solder joints by eliminating the need to push wires through an already

established solder connection.

Check and double check the traces on the back of the turretboard. (this is one of the most common areas

that mistakes are made).

If you plan on doing modi cations such as hot-rodding (adding a bright switch etc.) and have never put

a kit together before, it is suggested that you assemble the basic amp and have it functioning properly, to

have an understanding of how the amp works before you start modifying it.

Photo 5 - Turretboard Assembly

Photo 6 - Fiter Cap Wiring

Mojotone British 100 Watt Style Amp Kit Manual 2012 Page 4

Internal Wiring Follow the color coded wiring diagram closely, twist the lament wires (6.3v heater wires) together from

transformer and between tube sockets to reduce hum from 120ac voltage.

Place entire turretboard inside the chassis noting the orientation (see schematic)

Connect corresponding wires to hardware, try to keep wire short and runs as neat as possible. This will

help make future troubleshooting and repair easier.

On each power tube socket, solder (1) 5W 1K ohm resistor from pin 4 to 6.

Try to avoid crossing wires over each other.

Before you plug the amp in check and re-check your wiring. If you are not clear on any part of the

circuit, ask someone.

Photo 8 - Internal Wiring

Photo 7 - Power Tube Socket

Mojotone British 100 Watt Style Amp Kit Manual 2012 Page 5

Photo 9 - Internal Wiring

Photo 10 - Input Jack Wiring

Mojotone British 100 Watt Style Amp Kit Manual 2012 Page 6

**WARNING**

The Voltages found inside your amp can cause serious harm or even death. Never

attempt to service your amp while a power source is connected.

Testing the Amp *WARNING* Never stick your hands inside ampli er especially while power is on!

Plug in speaker

Turn amp on without tubes installed rst, checking transformers and components for shorting, excessive

heat, arcing, smoking, etc.

Test tube socket voltage with a multimeter to ensure correct operation.

Turn Amp off before putting tubes in proper location, and allow tubes to heat up for approx. 30 secs. Before

playing at volume.

Listen. The best way to tell if there any problems with the circuit of the amp and/or tubes is just to listen....

excessive noise, popping/ crackling, hum, loud squeals, as well as ghost- echo sounds. These are all

symptoms of many common problems in tube amps.

If you need to service the amp after having it on, you must discharge the capacitors. This is done by

unplugging the amp, turning the power and standby to the on position and letting it sit for 30 mins. or so.

Always use a multimeter to check the residual voltage in the cap to make sure it is fully discharged.

Feel free to call Mojo at 1-800-927-Mojo (6656) at any time if you any questions regarding your kit.

Thanks for choosing Mojo and dont forget to crank it up!!

**WARNING**

The Voltages found inside your amp can cause serious harm or even death. Never

attempt to service your amp while a power source is connected.

Online Resources

Grounding principles: www.aikenamps.com/StarGround.html & www.el34world.com/charts/grounds.htm

Signal Flow Diagram: www.el34world.com/charts/current ow.htm

Printed Resources

The Tube Amp Book by Aspen Pittman

A Desktop Reference of Hip Vintage Guitar Amps By Gerald Weber

All About Vacuum Tube Guitar Ampli ers By Gerald Weber

Photo 11 - Internal Wiring - Preamp