Fender KXR100 Service Manual

KXR 100

KEYBOARD EXTENDED RANGE

SERVICE MANUAL

CONTENTS:

Notices

Specifications

Theory of Operation

Parts lists:

Preamp

Power Amp

Chassis assembly

Cabinet assembly

Miscellaneous

Schematics/diagrams

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

KXR 100

(This is the model name for warranty claims)

KEYBOARD EXTENDED RANGE

SERVICE MANUAL

FEBRUARY 1995 REV A

TYPE PR262

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

KXR 100

SPECIFICATIONS

Part Number: 120V Version : 22-8501

230V Version : 22-8561

Power Amp Section

Power output: 80 Watts RMS
Sensitivity: 370mV RMS
Input impedance: 33K Ω
Rated Load Impedance: 4 ohms
Distortion at rated power: Less than .1% @ 1kHz, before compression
Less than 1% @ 1kHz, maximum compression
DELTACOMP™ range: 20dB

PREAMP SECTION:

Input Impedance: XLR – 10k Ω

¼” phone – 36 k Ω

Sensitivity for 80 watts: XLR – 2.8 mV
CHANNEL and MASTER ¼” phone – 28mV
VOLUME at maximum

all tone controls at “0”

Equalization Range: Low +/- 12dB at 100Hz

Low Mid +/- 12dB at 338Hz
High Mid +/- 12DB at 1588Hz
High +/- 12dB at 4 kHz (shelving)

Dimensions: Height:27 1/2" (69.8 cm)

Width: 20 1/2 " (52.1 cm)
Depth: 12" (30.5 cm)

Weight: 55 lbs. (25 kg)

Product specifications are subject to change without notice

KXR 100

THEORY OF OPERATION

The Channel One input will accept a Balanced or Unbalanced signal via a ¼” Phone plug or a 3 pin XLR
connector. U1B provides a gain of 1 for the ¼” input, and a gain of 10 for the XLR input. A balanced low
level microphone connected to Channel One, allows the KXR 100 to function as a small self contained
Vocal and Instrument PA system. U1B also rolls off high frequencies at about 128kHz.

Located within the negative feedback loop of U1A is the Channel One Volume control. It provides a
minimum gain of 1, and a maximum gain of 15. At maximum gain, Capacitor C6 rolls off the high
frequencies at about 47kHz. Channel’s Two and Three do not offer a low level XLR input Jack. They do
offer a function that shorts across the Volume control via a switch contact in the ¼” input jack. This causes
U2A and U3A to remain locked into a Unity Gain mode, disabling the Volume control, until a plug is
inserted into the jack. This reduces noise in the input circuitry.

The three channels sum together and feed the Reverb Drive stage U4A and the Summing Amp U5A. U4B
senses the return signal from the Reverb Pan. R70 and C47 provide a slight boost in the high frequencies,
R29 and C20 roll off low frequencies. This produces a fairly bright reverb sound. To eliminate noise, C49
limits the high frequency response to about 5kHz. All ground connections in the Reverb circuitry are routed
through a dedicated trace to the Star Ground point on the circuit board. This eliminates any bleed through
of noise into other audio ground paths.

U5A sums the dry signal with the Reverb return signal and then drives the Equalizer circuit. Gyrators U6B,
U7B, and U7A are used for the low (100Hz), Low Mid (338Hz), and High Mid (1588Hz)bands. The High
band uses a single pole shelving filter (R47, C34) at 4kHz. U6A performs the Boost/Cut function, and also
drives the Effects Loop.

The Effects Loop Send is capable of providing a pseudo balanced signal if desired. This helps to reduce
hum. The Effects Loop Return will accept an Unbalanced or Balanced input.

U5B drives the Record Out jacks, and the Master Volume control. R55 and C40 boost the low frequencies
at 220Hz. This boost is not desired at the Record Out jacks. Therefore C41 and R56 remove the Low
boost. This allows the Record Out to see the same signal as the input channels, plus any tone shaping
from the Equalizer. Between the ouptput of U5B and the Master Volume control, C43 and R60 boost high
frequencies. The boost in Low and High frequencies provide a Smile Curve response.

The signal and ground line from the Master Volume control feed through a Flex Jumper to U2A, which is on
the Power Amp circuit board. Any Hum induced into the signal and ground line is canceled by the
Common Mode Rejection at U2A.

Using R71 and C60, U2A provides the high frequency pre-emphasis from about 1kHz on up. This prevents
compressor “pumping” caused by very low frequencies. The increase in high frequencies prevents
repetitive releases by the compressor when triggered by low frequencies. De-emphasis occurs just prior to
the speaker connections, on a small break-away circuit board that contains R72, R73, and C61.