Fender Ultimate-Chorus-SM Service Manual

ULTIMATE CHORUS

SERVICE MANUAL

CONTENTS:

Notices

Specifications

Parts lists:

PCB assembly

Chassis assembly

Cabinet assembly

Footswitch assembly

Miscellaneous

Schematics/diagrams

Fender Musical Instruments Corp. 7975 North Hayden Road Scottsdale, AZ 85258

ULTIMATE CHORUS

(This is the model name for warranty claims)

SERVICE MANUAL

JUNE 1995

IMPORTANT NOTICE:

The information contained herein is CONFIDENTIAL and PROPRIETARY to Fender Musical Instruments Corp. It is
disclosed solely for use by qualified technicians for purposes of equipment maintenance and service. It is not to be
disclosed to others without the expressed permission of Fender Musical Instruments Co. All specifications subject to
change without notice.

For warranty repair service, only Fender specified part numbers are to be used. It is recommended they also be used
for post-warranty maintenance and repair.

Parts marked with an asterisk (
and SAFETY requirements. DO NOT USE A SUBSTITUTE!

A coded naming convention is used in the description of certain parts. The codes and what they mean are as follows:

CAPACITOR CODES HARDWARE CODES

CAP AE = Aluminum Electrolytic BLX = Black Oxide
CAP CA = Ceramic Axial CR = Chrome Plated
CAP CD = Ceramic Disk HWH = Hex Washer Head
CAP MPF = Metalized Polyester Film M = Machine Screw
CAP MY = Mylar NI = Nickel Plated
CAP PFF = Polyester Film/Foil OHP = Oval Head Phillips

RESISTOR CODES

RES CC = Carbon Comp SMA = Sheet Metal "A" Point
RES CF = Carbon Film SMB = Sheet Metal "B" Point
RES FP = Flame Proof SS = Stainless Steel
RES MF = Metal Film TF = Thread Forming
RES WW = Wire Wound ZI = Zinc Plated

*

) indicate the required use of that specific part. This is necessary for RELIABILITY

PB = Particle Board
PHP = Pan Head Phillips
PHPS = Pan Head Phillips Sems

ULTIMATE CHORUS

SPECIFICATIONS

Product Release No.: PR 204 (This is not a model number)

Input Impedance: Greater than 1M Ohm

Nominal Level: 100mV

Power output: 65 Watts RMS @ 5% T.H.D. per channel =

130 Watts RMS

Rated Load Impedance: 8 ohms per channel

Mono Effects Loop: Output impedance: 1kΩ

Input impedance: 25kΩ
Nominal level: -10dBV

Stereo Effects Loop: Nominal Level: -10dBV

Output Impedance: 1k Ohms
Input Impedance: 94k Ohms
Specifications for each channel –
Left on Tip, Right on Ring

Dimensions: Height:18 1/2" (47.0 cm)

Width: 26 1/8” (66.0 cm)
Depth: 10 1/4" (26.0 cm)

Weight: 47 lbs. (21.3 kg)

Product specifications are subject to change without notice

THEORY OF OPERATION

NORMAL CHANNEL

The first stage (U1A) sets up the initial response of the amplifier. It provides a second order high-pass filter
with a 3dB down point of 60 Hz, and a gain of about 4. The output of U1A splits to feed the NORMAL and
DRIVE channels. For the NORMAL channel, the signal feeds through the NORMAL VOLUME control
(R11) to U1B. The output of U1B drives through the tone controls and feeds summing amplifier U4A.

DRIVE CHANNEL

The signal from U1A feeds a special tone-shaping circuit which optimizes the frequency response for the
distortion circuit that follows. U2A provides the variable gain adjustment that drives the distrotion circuit. It

also acts as a bandpass filter with 3db down points at 90Hz and 4kHz. JFET Q2 mutes the input to the
distortion circuit when in the NORMAL channel mode. Diodes CR4 and CR5 are used as a voltage clamp
to prevent excessive voltage from damaging the JFET. U2b is the distortion circuit. The signal couples to