IMPORTANT NOTICE This manual has been provided for the use of authorized Yamaha Retailers and their service personnel. It has been assumed that basic service procedures inherent to the industry, and more specifically Yamaha Products, are already known and understood by the users, and have therefore not been restated.
F-20B SPECIFICATIONS Rated Output Power: Speaker: 25cm x 1 Controls: VOLUME, TREBLE, HIGH MID, LOW MID, BASS, Input Level Select Switch (PASSIVE/ACTIVE) Input/Output Terminals: INPUT, AUX IN, PHONES Power Consumption: 25W/120V (UL, CSA) 25W/230V (E, BS) Power Requirements: U.S. and Canadian mod-...
F-20B CIRCUIT BOARD LAYOUT Top View Side View AC Cord MAIN Power Transformer MAIN MAIN MAIN Front View MAIN BLOCK DIAGRAM MAIN GAIN SELECT ACTIVE CH. PASSIVE CH. AUX IN +12V INPUT ACTIVE TYPE TONE CONTROL IC1,IC2 VOLUME OP AMP...
F-20B DISASSEMBLY PROCEDURE Pre-Main Unit (Time required: about 2 min) Remove the eight (8) screws marked [A]. The back board can then be removed. (Fig.1) Pull out the speaker wires. (Fig.1) Remove the four (4) screws marked [30]. The pre- main unit can then be removed by sliding it backward.
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F-20B MAIN 2/2 Circuit Board (Time required: about 3 min) Remove the pre-main unit. (See Procedure 1) Remove the screw marked [C80]. The MAIN 2/2 circuit board can then be removed. (Fig.3, Fig.5) Power Transformer (Time required: about 4 min) Remove the pre-main unit.
F-20B CIRCUIT BOARDS MAIN1/2 CIRCUIT BOARD GAIN INPUT VOLUME TREBLE SELECT to POWER to POWER SW TRANSFORMER from POWER to MAIN 2/2 CN4 from AC CORD TRANSFORMER FUSE VERSION INDICATION RATE J, U 250V 315mAL Must be erased Must be...
F-20B IC BLOCK DIAGRAM BA4558 (XO078A00) Dual Operational Amplifier MAIN: IC1,IC2,IC3 +DC Voltage Output A Supply Inverting Output B Input A Non-Inverting Inverting Input B Input A Non-Inverting -DC Voltage Supply Input B INSPECTIONS Preparation To inspect the main unit, the following jigs are required.
F-20B BASS AMPLIFIER PARTS LIST CONTENS OVERALL ASSEMBLY .................. 2 PRE-MAIN UNIT .................... 4 ELECTRICAL PARTS ..................6 Note) DESTINATION ABBREVIATIONS Australian model South African model British model Chinese model Canadian model South-east Asia model German model Taiwan model European model U.S.A.
<P.1> OVERALL CIRCUIT DIAGRAM F-20B D2SBA20 (VP344100) MAIN DIODE STACK 1.5A 200V GAIN SELECT OP AMP OP AMP OP AMP OP AMP OP AMP AUX IN INPUT BASS LOW MID HIGH MID TREBLE MAIN OP AMP OP AMP VOLUME HIFI AMP...