Frontman_15B_Service_Manual 电路图.pdf
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1、FRONTMAN 15B p/n 022-1503-000 (120 V) SERVICE MANUAL CONTENTS: Notices Specifications Parts lists: Theory of Operation PCB assembly Chassis Assembly Cabinet assembly Miscellaneous Schematics Service diagram Fender Musical Instruments Corp.,7975 North Hayden Road Scottsdale, AZ 85258 FRONTMAN 15B (Th
2、is is the model name for warranty claims) SERVICE MANUAL FEBRUARY 1997 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
3、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 a
4、nd 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 mean are as follows: CAPACI
5、TOR 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=Particle Board RESISTOR C
6、ODESPHP=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 1 RadioFans.CN 收音机爱 好者资料库 FRONTMAN 15B SPECIFICATIONS Prod
7、uct Release No.:PR 359 (This is not a model number) PART NUMBER:22-1503120 V 22-1533240 V Aus 22-1543230 V UK 22-1563230 V 22-1573100 V 22-1583230 V Nord POWER AMPLIFIER SECTION: Power output:15 Watts Rated load impedance:8 Distortion at rated power:5% Power bandwidth:40 Hz to 20 kHz Compression ran
8、ge:19dB PREAMP SECTION: Input impedance:202k Ohms Sensitivity ( 1kHz):4mV at onset of compression Equalization range:HIGH +/- 15 dB at 8 kHz MID+/- 15 dB at 800 Hz LOW+/- 15 dB at 40 Hz PHYSICAL SPECIFICATIONS: Width:13-1/4 inches (34.3 cm) Height:15 inches(38.1 cm) Depth:9-3/4 inches(24.8 cm) Weigh
9、t:21 lbs.(9.5 kg) FRONTMAN 15B THEORY OF OPERATION The input circuitry is a low pass filter with the -3 dB down point at 22 kHz. This sets up the initial response of the amplifier and provides RF suppression. U1B is an Auto Pad. It provides excellent headroom and low noise. At upper volume control s
10、ettings, it also rolls off low frequencies at 219 Hz. U1A makes up the tone controls. They provide 15 dB of boost or cut at 40 Hz (Low), 800 Hz (Mid), and 8 kHz (High). U2B is a special tone shaping circuit used for sonic enhancement. U2A is a unity gain amplifier which drives the power amp stage. I
11、n conjunction with U4, it acts as the gain reduction circuit for the Deltacomp. The output of the power amplifier is sensed through R23 by the Comparator U5A. As the amplifier output approaches clipping, the output of U5A goes negative. This charges Capacitors C20-C23 through the time constant made
12、up with R41 (3.9K x 8.8F = 34.3mSec). This single-pole charge is the attack time for the Deltacomp. As the capacitors charge, the voltage at the base of transistor Q1 goes negative, turning on this Darlington device. Current from Q1 controls the output voltage of U4 (Operational Transconductance Amp
13、lifier). The output of U2A also drives the inverting input of U4. The inverted output from U4 mixes with the non-inverted input to U2A causing a cancellation effect. This attenuates the signal to the power amp, thus eliminating clipping. When the power amp output is reduced, the output U5A goes posi
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