Mod K-700 Manuel utilisateur
Use these instructions and your vintage Fender guitar amplifier to learn:
How to convert the “Bass Instrument” channel of a Bassman amp into a tremolo
effect for the “Normal Channel”.
BASS TO TREMOLO CONVERSION KIT (K-700)
1Copyright © 2011 by modkitsdiy.com
100k
INTENSITY
50k-
RA
220k
.01µ
.modkitsdiy.com
Table of Contents
Safety ……………………………………………………3
arts List ……………………………………………4, 5
Tools …………………………………………................6
Soldering Tips ……………………………………7, 8
reliminaries ……………………………………………9
Test oints …………………………………………...10
Bass to Tremolo Modification …………………...11 – 24
2
Style A …………………………………………...12 – 17
Style B ……………………………………………18 – 23
Schematics …………………………………………...12, 18
Terminal Strip Mounting Tips …………………...24
DANGER HIGH VOLTAGE MAY BE PRESENT
BE CAREFUL!
Safety
“Caution: to prevent electrical shock,
do not remove chassis or metal cover attached to chassis.
No user serviceable parts inside.
Refer servicing to qualified personnel only.”
-the back of an amp
We have quoted the back of an amp to stress the importance of putting safety first when
working on this type of equipment. Tube amps operate at high voltages which have the
potential to kill. Only work on an amp when you are wide awake and sober.
lease make sure you do the following before opening your amp:
Turn the power switch off.
Turn the standby switch off (down position).
Unplug the power cord.
Give the power tubes 10 minutes to cool down.
When the amp is open:
Use a volt meter with alligator clips to measure for high voltage at several test points.
(see the “ reliminaries” section for details)
Use the one-hand rule.
(see the “ reliminaries” section for details)
ON STANDBY
UNPLUG
OFF
3
4
.1µF
30V
bro n
black
yello
gold
100K
Parts List
art Number Quantity Description
C-MD1-630 1 0.1µF capacitor
C-MD01-630 2 0.01µF capacitor
C-MD022-630 1 0.022µF capacitor
.022µF
30V
.01µF
30V
R-A100K 3 100kΩ, ½W resistor
R-A1M 2 1MΩ, ½W resistor
bro n
black
green
gold
1M
R-A3M 1 3MΩ, ½W resistor
orange
black
green
gold
3M
R-A8D2M 1 8.2MΩ, ½W resistor
grey
red
green
gold
8.2M
R-A220K 1 220kΩ, ½W resistor
red
red
yello
gold
220K
R-A2D7K 1 2.7kΩ, ½W resistor
red
violet
red
gold
2.7K
C-ET22-50 2 22µF polarized capacitor
22µF 5 V
Parts List (continued)
art Number Quantity Description
R-VO 1020 1 Optocoupler
3
M
EG
5
0K
R-VC50K-RA 1 50kΩ potentiometer (reverse audio taper)
R-VC3M-RA 1 3MΩ potentiometer (reverse audio taper)
W-SC-11 1 ¼“ input jack
-H35-242 1 D DT slide switch
5
S-W809L 15 ft 20 AWG solid core hook-up wire (white)
-0501H 3 5 lug terminal strip (3rd lug common)
R-B1D5K 1 1.5kΩ, 1W resistor
bro n
green
red
gold
1.5K
(This value is used in amps with shared preamp tube
cathodes only – Like Bassman 100)
Tools
1. Digital Multi-Meter (DMM) – a meter for measuring voltage, current, resistance, and
sometimes capacitance.
2. Alligator Clip Test Leads – connect to your DMM for hands free measurements. These
are useful when setting the power tube bias and for safety when taking electrical
measurements.
3. Soldering Station – soldering iron with a 1/8” screwdriver tip and a variable control
capable of producing 25-40Watts. This will allow you to do some precise soldering of circuit
components and wires (do not use a soldering gun for soldering of electronic circuits).
4. Solder – 60/40 rosin core solder.
5. De-soldering Pump or Bulb – this will assist you in removing solder for circuit
modifications and correcting connection errors.
6. Wire Strippers
7. Cutting Pliers – These are great for cutting leads on resistors, capacitors, etc. before and
after soldering.
8. Needle Nose Pliers – 6” long are good for bending component leads and holding
components leads while de-soldering.
9. Screwdrivers – hillips
Soldering Tips (circuit boards)
Work in a ventilated area with a fan to blow the smoke from your face.
Allow the soldering iron to heat up to the point where the solder melts quickly when
touched to the iron's tip.
Clean the soldering iron's tip by wiping it across a wet sponge before applying solder
to it.
Be very careful not to unintentionally burn any wires in the vicinity of the soldering
iron.
De-soldering Tip
2. If necessary,
add new solder
to the connection
point to help it
become a liquid.
1. Heat up the
connection point
until it starts
smoking and
becomes a liquid.
3. Remove the
component lead
from the
connection point
with needle nose
pliers.
Soldering Tip
2. Insert the
appropriate
component lead with
needle nose pliers.
2. Heat up the
connection point
until it becomes a
liquid.
1. Cut and bend the
component leads for
a neat fit to their
connection points.
7
Soldering Tips (solder lugs)
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.
1. Bend the component lead
and rap 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 ith
the soldering iron.
4. Apply solder to both
component lead and
connection point.
2. Apply fresh solder to mix in
ith old solder joint
1. Heat up old solder joint
ith the soldering iron.
3. Use a de-soldering tool to
remove the old solder joint
hile it is heated.
De-Soldering Tip
8
UNPLUG
ON STANDBY
OFF
COOL
Preliminaries
lease make sure you do the following before opening your amp:
Unplug the power cord.
Turn the power switch off.
Turn the standby switch off (down position).
Give the power tubes 10 minutes to cool down.
Make sure the power tubes have cooled down enough to touch.
Remove all of the tubes from the amp and store them someplace safe.
Remove the amplifier chassis from its cabinet and set it on a safe workplace.
ON STANDBY
When the amp is open:
Follow the one hand
rule and use a volt meter with
alligator clips to measure for
high voltage at several test
points.
The one hand rule (pictured above): is a safety precaution for working on an amp that is
plugged in or could potentially have high voltages present. Using alligator clips with your
DMM, clip the ground side to the chassis and use the other side to probe at various test points
with one hand. This prevents a fatal shock which can result from current passing through the
heart. (Many people even put their other hand in their pocket or behind their back).
(test points are on the next page)
9
Test Points
If there is a high voltage present at any of these test points, there may be something
wrong with your amp. lease have it checked by a qualified repair shop.
TP(1), TP(2): These test points are both on the standby switch. When the amp is in
operation, these two points have a very high voltage present. By 10 minutes after
turning off the standby and power switches, all the voltage should have been drained.
TP(3): This is the anode side of a solid state diode.
TP(4), TP(5): These test points are the cathode pins of the preamp tubes. It is not a
bad idea to check these two pins on each one of the preamp tubes.
(Tube Rectifier TP: If your amp has a GZ34/5AR4 tube and no standby switch, then
check the GZ34 pins 2 and 8 for voltage.)
1
7
6
5
4
3
2
8
9
VOL
TREB
BASS
1
7
6
5
4
3
2
8
1.5K
470
1
7
6
5
4
3
2
8
470
1.5K
NORMAL
21
BRIGHT
MASTER
VOLUME
Je el
Lamp
Holder
POWER STANDBY
TP(1)
TP(2)
TP(3)
TP(4)
TP(5)
470
Inside View of Amp Chassis - not all components are shown
10
Table des matières
