Boss BF-2 flanger pedal schematic
Fig. 1: Boss BF-2 flanger guitar pedal schematic diagram
The BF-2 was first sold in 1980, but it's still is one of the most commonly used analog flanger pedals. The 4 knobs (manual, depth, rate and resonance) allow the users to shape the sound as desired -- from dynamic jet-plane effects to short delay, chorus and vibrato sounds.
Fig. 2: Boss BF-2 flanger circuit board - component side
- 4 controls: Manual, Depth, Rate and Resonance (Res)
- Connectors: Input, Output, AC Adaptor
- Input impedance: 470k
- Residual noise: -95dBm (IHF-A)
- Output load impedance: over 10k
- Delay Time: 1ms - 13ms
- LFO speed: 100ms - 16s
- Recommended AC Adaptor: ACA or PSA Series -- depending on production year
- Current draw: 15mA DC at 9V
- Weight: 400 g (0.88lbs.)
- Dimensions: 70(W) x 55(H) x 125(D) mm. (2.8" x 2.2" x 4.9")
ICs, transistors and diodes used in the Boss BF-2:
- IC1, IC2: uPC4558C (dual operational amplifier)
- IC3: MN3207 (1024 stage BBD)
- IC4: MN3102 (BBD driver)
- IC5: TL022CP (dual low-power general-purpose operational amplifier)
- IC6: uPC78L05 or equivalents (5V positive voltage regulator)
- Q1, Q2, Q3: 2SC732TM-GR (NPN silicon transistor)
- Q4: 2SK30A-Y (Silicon N-channel junction field effect transistor)
- Q5: 2SA733-P (PNP silicon transistor)
- Q6-Q11: 2SC945-P (NPN silicon transistor)
- D1: RD11EB-3 (11V 500mW Zener diode)
- D2: RD5.1EB-3 (5.1V 500mW Zener diode)
- D3-D10: 1S2473 or 1S1588 or DS442 (switching diodes)
1.) Clock frequency adjustment:
Set MANUAL and DEPTH knobs to full counterclockwise. Connect an oscilloscope to TP-1 test point. Adjust VR7 for T=25us (40kHz). Rotate the MANUAL knob fully clockwise. T should be 2uS +/-20%.
2.) BBD bias:
Set DEPTH and RES. knobs full counterclockwise.
Feed a 200Hz, sine wave, 0dBm signal into the INPUT jack. Connect the oscilloscope to Q3's emitter. While turning MANUAL across its entire rotation range, set VR6 for a clip-free waveform at the peaks.
Set MANUAL, DEPTH knobs full counterclockwise and RES. knob full clockwise. Plug short circuit into INPUT jack. Connect OUTPUT jack to an amplifier and speaker. While touching a screwdriver to TP-2, set VR5 to the point where oscillation begins.
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