Power Supply; Footswitch Control; Panel Pcb - Fender BASSBREAKER 007 Combo Service Manual

POWER SUPPLY

The Power Supply circuitry is found on the POWER
SUPPLY PCB. Its circuitry is typical of a Fender
tube amplifier. The secondary side of the Power
Transformer consists of 3 windings: high-voltage
winding, low-voltage winding and heater winding.
The high voltage secondary winding is used to gen-
erate the high voltage DC power supplies in the
amplifier. The high voltage DC power supply is en-
ergized through a
configuration to filter cap C15. The "voltage-drop"
resistors R11 thru R13, along with their associated
filter capacitors C11-13, provide the DC plate or
screen-grid voltages that are used to bias the tube
stages in the design. These supplies are routed to
the TUBE PCB circuitry through 18 AWG wiring.
The low voltage secondary winding feeds a full-
wave bridge & filter configuration to create input DC
voltages for regulators U1 & U2. These heat-sinked
ICs generate the low voltage +/-16V DC power
supply. A primary function of this circuitry is to pro-
vide DC filament drive to the V1 & V2 heaters. The
DC bipolar filament voltages couple to the heaters
through R9 & 10 on the POWER SUPPLY PCB. A
cable connects this supply to the filament on the
TUBE PCB. A cable also connects the low voltage
supplies to the REAR PANEL PCB to power the
control circuitry described later.
.
full-wave bridge rectifier
BASSBREAKER™ 007
(This is the model name for warranty claims)
The heater secondary winding produces a 6.8VAC
power supply that energizes the EL-84 (V3) heat-
er's filament only. This secondary is connected to
terminals on the TUBE PCB.
The POWER INDICATOR LED is energized by the
positive low voltage regulated supply on the POW-
ER SUPPLY PCB. The LED is routed for insertion
into the rear of the front panel jewel with power
connections through its red & white wires.

FOOTSWITCH CONTROL

The FOOTSWITCH circuitry is found on the REAR

PANEL PCB.

This circuitry allows footswitch or
front panel control of the TREBLE BOOST feature.
Note that with a footswitch inserted in J1, it defeats
any control capability from the control panel's TRE-
BLE BOOST switch.
electronic switch for the TREBLE BOOST whether it
is controlled by the control panel switch (S1) or the
optional footswitch (7706424000) according to the
logic described above.
One cable connects the REAR PANEL PCB to the
CONTROL PANEL PCB to connect the control pan-
el's TREBLE BOOST switch to the base of Q1.
Another cable connects the REAR PANEL PCB to
the TUBE PCB to provide the TREBLE BOOST
control signal to the gates of the Q2 & Q3 switching
circuits described in the PRE-AMPLIFIER section.
Transistor Q1 acts as the
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