Download Mojotone Tweed Princeton Style Amp Kit Instruction

Mojotone® Tweed Princeton Style Amp Kit
Instruction Manual
Tools needed for build: (Photo 1)
40 Watt 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
Photo 1 - Lay out parts for quick inventory.
1.
Lay out parts for a quick inventory (Photo 1)
2.
Compare physical inventory to the included bill of materials. (Packaging mistakes are
rare for Mojo but double check us before you start your build.)
3.
Install chassis mounted hardware
4.
Tube Sockets - Install so that they all face the same direction, noting pin #1 orientation.
5.
Power Transformer – Make sure to mount the PT so the label faces toward tube sockets.
(This will be helpful for anyone looking at the transformer mod. number without having to
take the chassis out of the amp.)
6.
Output Transformer - Feed wires through grommets and note wire locations.
7.
Install and orient potentiometers so the lugs are facing up.
8.
Install Input and Output Jacks (lugs facing up)
9.
Fuse Holder (Install fuse at same time so you won’t forget.)
10. Pilot Light Assembly (with bulb and lens)
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Photo 2 - Install chassis mounted hardware
Photo 3 - Install chassis mounted hardware
©Mojotone® Tweed Princeton Style Amp Kit Manual 2012
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Photo 4 - Fiberboard Assembly
1. Fiberboard Assembly (Pictures 4 and 5)
a) Always try to rely more on the schematic than the wiring diagram in any circuit.
b) (2) ½ w 100 Ohm resistors - Solder from the pilot light to ground.
c) (1) ½ w 1 Meg resistor from Input 1 to ground tied to Input 2. This accomplishes the noise
back to ground when unplugged
d) Be sure of component placement and orientation, especially capacitors (positive,
negative)
e) If you plan on doing modifications such as “hot-rodding” (ie. 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 begin modifying it.
f)
Check and double check the traces on the back of the fiberboard. (This is one of the most
common areas that mistakes are made.)
Photo 5 - Fiberboard Assembly
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2. Internal Wiring
a) Follow the color coded wiring diagram closely, remember to twist your filament (heater
wires), to reduce hum from AC voltage (6.3) going through the wire.
b) Have enough of the power cord inside chassis to reach fuse, switch and ground.
c) Affix the floating fiberboard, noting it is held in place by the wires, attach backing with
rubber cement if necessary (or mount directly to chassis).
d) Place entire fiberboard inside the chassis noting the orientation (see schematic).
e) Connect corresponding wires to hardware, while trying to keep wire short and runs as neat
as possible. This will help make future troubleshooting and repair easier.
f)
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).
g) Try to avoid crossing wires over each other (other than heater wire).
h) Before you plug the amp in check and re-check your wiring. If you are not clear on any part
of the circuit, ask a qualified technician.
3. Testing the Amp
a) *WARNING* Never stick your hands inside amplifier especially while power is on!
b) Test tube socket voltage with a multimeter to ensure correct operation.
c) Plug in speaker
d) Turn amp on without tubes installed first, checking transformers and components for
shorting, excessive heat, arcing, smoking, etc.
e) Turn Amp off before putting tubes in proper location, and allow tubes to heat up for approx.
30 seconds before playing at volume.
f) 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 ghostecho sounds. These are all symptoms of many common problems in tube amps.
g) 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. If you do not have a standby switch, you will need to short the
capacitor positive leads to ground with a pair of pliers or an insulated wire. It is common to
hear a pop when this is done. This is just the cap discharging itself. Always use a
multimeter to check the residual voltage in the cap to make sure it is fully discharged.
h) Feel free to call Mojo at 1-800-927-Mojo (6656) at any time if you any questions regarding
your kit.
i)
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® Tweed Princeton Style Amp Kit Manual 2012
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