KXR_60_Service_Manual 电路图.pdf
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1、KXR 60 KEYBOARD EXTENDED RANGE SERVICE MANUAL CONTENTS: Notices Specifications Circuit Description Parts lists: PCB assembly Chassis assembly Cabinet assembly Miscellaneous Schematics/diagrams Fender Musical Instruments Corp. 7975 North Hayden Road Scottsdale, AZ 85258 RadioFans.CN 收音机爱 好者资料库 KXR 60
2、 KEYBOARD EXTENDED RANGE (This is the model name for warranty claims) SERVICE MANUAL MARCH 1996 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 mai
3、ntenance 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 po
4、st-warranty maintenance and repair. Parts marked with an asterisk (*) indicate the required use of that specific part. This is necessary for RELIABILITY 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 me
5、an are as follows: CAPACITOR CODES HARDWARE CODES CAP AE=Aluminum ElectrolyticBLX=Black Oxide CAP CA=Ceramic AxialCR=Chrome Plated CAP CD=Ceramic DiskHWH=Hex Washer Head CAP MPF=Metalized Polyester FilmM=Machine Screw CAP MY=MylarNI=Nickel Plated CAP PFF=Polyester Film/FoilOHP=Oval Head Phillips PB=
6、Particle Board RESISTOR CODESPHP=Pan Head Phillips PHPS=Pan Head Phillips Sems RES CC=Carbon CompSMA=Sheet Metal A Point RES CF=Carbon FilmSMB=Sheet Metal B Point RES FP=Flame ProofSS=Stainless Steel RES MF=Metal FilmTF=Thread Forming RES WW=Wire WoundZI=Zinc Plated RadioFans.CN 收音机爱 好者资料库 KXR 60 SP
7、ECIFICATIONS Product Release No.:PR 299 (This is not a model number) POWER AMPLIFIER SECTION: Power output:50 Watts RMS Distortion at 50 Watts:Less than .1% 1kHz, before compression Less than 1% 1kHz, maximum compression Rated load impedance:8 Sensitivity:370 mV RMS Input impedance:33K DELTACOMP Ran
8、ge:20dB PREAMP SECTION: Input Impedance:36k Sensitivity for 50 watts:28 mV CHANNEL and MASTER VOLUME at maximum all tone controls at “0” Equalizer:Low +/- 12dB at 100Hz (shelving) Low Mid +/- 12dB at 338Hz High Mid +/- 12dB at 1188Hz High +/- 12dB at 4 kHz (shelving) DIMENSIONS:Height:22(55.9 cm) Wi
9、dth: 18(45.7 cm) Depth: 12(30.5 cm) Weight:46 lbs.(21 kg) Product specifications are subject to change without notice RadioFans.CN 收音机爱 好者资料库 KXR 60 CIRCUIT DESCRIPTION Preamp The Channel One input will accept a Balanced or Unbalanced signal via a ” Phone plug. U1B provides a gain of 1, and rolls of
10、f high frequencies at about 128kHz. The signal then couples to the second half of the input stage. 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 frequenci
11、es at about 47kHz. The input stage also features a function that shorts across the Volume control via a switch contact in the ” input jack. This causes U1A 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 c
12、ircuitry. Channel Two is identical to Channel One. The two channels sum together to feed the Reverb Drive stage U3A, and the Summing Amp U4B. U3B senses the return signal from the Reverb Pan . R24 and C19 provide a slight boost in the high frequencies . R23 and C18 roll off low frequencies. This pro
13、duces a fairly bright reverb sound. To eliminate noise, C17 limits the high frequency response to about 5kHz. All ground connections in the Reverb circuitry are routed through a dedicated Reverb Ground trace to the Star Ground point on the circuit board. This eliminates any bleed through of noise in
14、to other audio ground paths. U4B sums the dry signal with the Reverb return signal and then drives the Equalizer circuit. Gyrators U5B, U6B, and U6A are used for the Low (100Hz), Low Mid (338Hz), and High Mid (1588Hz) bands. The High band uses a single pole shelving filter (R40,C31) at 4kHz. U5A per
15、forms the Boost/Cut function, and also drives the Effects Loop. The Tape in jacks are buffered by U7A and sum with the main signal just prior to the Effects Loop. The Effects Loop Send is capable of providing a pseudo balanced signal if desired. This helps to reduce noise and hum. The Effects Loop R
16、eturn will accept an Unbalanced or Balanced input. U7B buffers the signal from the Effects Loop, and drives the Master Volume control. R55 and C39 boost the low frequencies at 220Hz. Between the output of U7B and the Master Volume control, C40 and R56 boost high frequencies. The boost in Low and Hig
17、h frequencies provide a slight “Smile Curve” response. DELTACOMP U8B is a unity gain amplifier that drives the power amp stage. U9 (CA3080A) is an Operational Transconductance Amplifier (OTA). In conjunction with U8B, it acts as the gain reduction circuit for the Deltacomp. The attack/release circui
18、t for the DeltaComp contains the Diode, Resistor, and Capacitor network that drives the base of Q8 (MPSA63). Comparator U4A senses the output of the power amplifier. As the amplifier approaches clipping, the output of U4A toggles negative. The negative voltage through Diodes CR14-17 charges Capacito
19、rs C54-C57 all at once in parallel as a one-pole filter through a single time constant made up with R84. R84X (C54+C55+C56+C57) = 2.2K x 8.8uF = 19.4mSec. KXR 60 DELTACOMP (CONT) As the capacitors charge, the negative voltage at the base of transistor Q8 turns on this Darlington device. Current flow
20、s from the Collector of Q8 to pin 5 of U9. This current controls the output amplitude of U9. The inverted output from U9 mixes with the signal at the input of U8B (pin 5) causing cancellation, which reduces the input to the power amplifier. This prevents the amplifier from clipping. When the output
21、of the power amplifier is reduced, the Comparator toggles positive, removing the negative control voltage from the attack/release circuit. The blocking action of Diodes CR14-CR17 force Capacitors C54-C57 to discharge(Release) through a 4-pole filter with different time constants, through Resistor R8
22、5. Turn-on delay JFET Q7 and associated components provide a 2 - 3 second turn-on delay for the audio input to the power amplifier. Upon power-up, the negative16 volts charges Capacitor C45 through Resistor R64. The negative gate voltage pinches off the JFET, removing the ground from the input of th
23、e amplifier. When switching the power off, C45 immediately discharges through Diode CR1, grounding the input of the amplifier. TROUBLE SHOOTING TIP: Check for proper operation of this circuit when experiencing excessive turn- on or turn off “Pops”, or no output when signal applied to the input. Many
24、 times the JFET itself can be the culprit. NOTE: Excessive turn-off “Pops” can also be caused by uneven discharge fo the +/- power supplies. Usually a mismatch in the Filter Capacitors will cause this problem. Its easy to look at both supplies on an oscilloscope. Invert one scope input and check for
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