Download Mojotone 1484 Amp Kit Manual

Mojotone 1484 Amp Kit
Instruction Manual
Tools needed for build:
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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)
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Compare physical inventory to the included bill of materials. Packaging mistakes are rare for Mojo but
double check us before you start your build.
Photo 1 - Lay out parts for quick inventory
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Install chassis mounted hardware
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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.
Choke - Feed wires through grommets and note wire locations.
Install Potentiometers.
Install Input, Output Jacks, and Switches.
Fuse Holder - Install fuse at same time so you won’t forget.
Pilot Light Assembly (Lens and Bulb)
Photo 2 - Installing Chassis Mounted Hardware
Photo 3 - Installing Chassis Mounted Hardware
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Photo 4 - Mounting Output Transformer. Use (2) 4-40 Kep Nuts for spacing the transformer
between the chassis. This helps the transformer clear the turret board mounted below.
Photo 5 - If you are grounding to the back of the pot, use either scotchbrite pad
or sand paper to scuff the back of the pot so that the solder will adhere.
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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)
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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)
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.
If you plan on doing modifications 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 6 - Turretboard Assembly
Internal Wiring
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Follow the color coded wiring diagram closely, twist the filament wires (6.3v heater wires) together from
transformer and between tube sockets to reduce hum from 120ac voltage.
NOTE: The filament wiring on V3 (6CG7) is different than the V1 & V2 (12AX7). Only connect filaments to
pins 4 & 5 on V3.
Use included (2) 3 lug terminal strips for installing rectifier diodes. (see picture below)
Place entire fiberboard 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) 2W 470 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 7 - Filament Wiring for V3 (6CG7) Preamp Tube
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Photo 8 - Rectifier Diode Wiring
Photo 11 - Internal Wiring
Photo 10 - Internal Wiring
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Photo 12 - Internal Wiring
Photo 13 - Internal Wiring
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**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
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*WARNING* Never stick your hands inside amplifier especially while power is on!
Plug in speaker
Turn amp on without tubes installed first, 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 don’t 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/currentflow.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 Amplifiers” By Gerald Weber
©Mojotone® 1484 Amp Kit Manual 2013
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