Yamaha Bass Amplifier Disassembly Procedure, Pre-MainUnit Time required about 2 min, F-20B

DISASSEMBLY PROCEDURE

1.Pre-Main Unit (Time required: about 2 min)

1-1 Remove the eight (8) screws marked [A]. The back board can then be removed. (Fig.1)

1-2 Pull out the speaker wires. (Fig.1)

1-3 Remove the four (4) screws marked [30]. The pre-

main unit can then be removed by sliding it backward. (Fig.1)

2.Speaker (Time required: about 2 min)

2-1 Remove the back board. (See Procedure 1-1)

2-2 Pull out the speaker wires. (Fig.1)

2-3 Remove the four (4) screws marked [60a]. The speaker can then be removed. (Fig.1)

3.MAIN 1/2 Circuit Board (Time required: about 4 min)

3-1	Remove the pre-main unit. (See Procedure 1)
3-2	Remove the five (5) knobs marked [P100] and the
	five (5) hexagonal nuts marked [C]. (Fig.5)
3-3	Remove the hexagonal nut marked [A120] and the
	hexagonal nut marked [A140]. (Fig.5)
3-4	Push the hooks of the spacer support (at the arrow
	symbol area of illustration) with a needle-nose plier
	to unlock.
	The MAIN 1/2 circuit board can then be removed.
	(Fig.2)	[30] x 4	Pre-Main Unit

F-20B

Pre-Main Unit [60a] Speaker

(Fig.1)

[A] BackBoard

Needle-nose plier

[30]: Truss Head Screw 4.0X25 MFZN2BL (VN347600)

[A]: Bind Head Tapping Screw 4.0X25 FCRM3-BL (EI340256)

[60a]: Bind Head Screw (VB403600)

[P40] MAIN1/2 Circuit Board

(Fig. 2)

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