Yamaha Bass Amplifier service manual F-20B 4.MAIN 2/2 Circuit Board, Time required about 3 min

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F-20B

F-20B

4.MAIN 2/2 Circuit Board

(Time required: about 3 min)

4-1 Remove the pre-main unit. (See Procedure 1)

4-2 Remove the screw marked [C80]. The MAIN 2/2 circuit board can then be removed. (Fig.3, Fig.5)

5.Power Transformer (Time required: about 4 min)

5-1 Remove the pre-main unit. (See Procedure 1)

5-2 While holding the nuts marked [P70] with a spanner, remove the two (2) screws marked [P60]. The power transformer can then be removed. (Fig.4)

MAIN1/2 Circuuit Board

[P70] [P60]

Power Transformer

[P80]

MAIN1/2 Circuuit Board

(Fig. 3)

(Fig.4)

 

Power Transformer

MAIN 2/2

[P40]

[P80]

[P70]

[P60]

[P40] [P60] [P70]

MAIN 1/2

[A120]

[P100], [C]

[A140]

[A120]: Hexagonal Nut 9.0 12X2 MFNI33 (LX200060)

[A140]: Hexagonal Nut 12.0 14X2 MFNI33 (ES200210)

[P60]: Pan Head Screw 4.0X10 MFZN2BL (V7018000)

[P70]: Hexagonal Nut #1 4.0 MFZN2Y (VB837300)

[P80]: Bind Head Screw-1 3.0X16 MFZN2BL (V7018100)

[P100]: Knob (V6955100)

(Fig. 5)

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Contents CONTENTS BASS AMPLIFIERIMPORTANT NOTICE F-20BWARNING CHEMICAL CONTENT NOTICE IMPORTANT NOTICE FOR THE UNITED KINGDOMSPECIFICATIONS PANEL LAYOUTF-20B POWER AMP BLOCK DIAGRAMCIRCUIT BOARD LAYOUT POWER TRANSFORMER2.Speaker Time required about 2 min DISASSEMBLY PROCEDURE1.Pre-MainUnit Time required about 2 min F-20B5.Power Transformer Time required about 4 min F-20B 4.MAIN 2/2 Circuit BoardTime required about 3 min CIRCUIT BOARDS F-20B3.Inspection procedure IC BLOCK DIAGRAM2.Power supply INSPECTIONSBASS AMPLIFIER CONTENSPARTS LIST F-20BF-20B OVERALL ASSEMBLY10 Overall Cabinet Assembly 20 Pre-MainUnitREMARKS F-20BDESCRIPTION New partsPRE-MAINUNIT F-20B V 6 9 5 4 8 0 0 ChassisELECTRICAL PARTS F-20BF-20B HF456330F-20B OVERALL CIRCUIT DIAGRAMABCDEFG P.1 5 F-20B