Help needed with Boss BF-2 Flanger

[Guga Ramone]

Hi! I'm new on this forum and I need some help with my Boss BF-2 Flanger:

1) When the pedal is on bypass mode I can hear some pulsating sound when the RATE knob is turned up. Is this normal with this pedal? Is there a way to fix it? Also, the D9 diode was defective in my pedal and I've changed it with an ordinary silicon diode. Can this change may be the cause for this problem?

2) Is there any simple mods that can be done to improve this little pedal?

BTW, here is the link for the circuit's schematic: http://www.geocities.com/CollegePark/Library/1355/Bf2.gif

Thank you in advance!!

PS: Sorry for my english. I'm from Brazil.

[Guga Ramone]

:?: No one? Help me, please!

[niftydog]

all I could suggest is to search the forum. It was only last week someone was talking about mods on this exact pedal.

[Fret Wire]

Judging by the schematic (which is hard to read clearly), D9 was not originally zener diode or anything unusual. Why was it defective? What happened to cause this? How are you powering the pedal? Any burn marks on the board? Double check to make sure it is orientated properly (cathode to ground) Your bypass bleed-through problem sounds like the JFET isn't turning off completely. It's not a common complaint with the BF-2, so a new jfet may take care of it. If indeed it's a jfet problem. The SD-1 has this bleed-through problem, and can be a bitch to cure.

[Mark Hammer]

Hi! I'm new on this forum

2) Is there any simple mods that can be done to improve this little pedal?

Welcome!  There are other members from Brazil.  I am sure if there are problems with the language they will be happy to help you.  I apologize for my VERY bad Portugese.  :lol:

There are many easy mods you can do to change the sound of the BF-2. Your ears will tell you if these are "improvements" or not.  For example:

a) C27 and C28 make up a non-polarized 16.5uf capacitor which sets the speed range.  If the capacitance value is reduced, the speed range goes higher.  Faster speed can produce an effect that sounds very much like a ring modulator.  I would suggest a pair of 4.7uf caps, back to back, as a suitable replacement.

b) Maximum flanging effect needs a 50/50 balance between delay and clean signal, but sometimes you want just a taste of flanging.  If the value of R29 is increased, the balance is shifted in favour of clean.  If you replaced R29 with a 22k fixed resistor, and a 100k pot, wired as a variable resistor (2 lugs, not all 3), you would be able to get everything from a *perfect* 50/50 balance to a much softer flanging effect, even with very high regen/res.

c) R11, D3, and D4 form a soft limiter, to keep high regeneration/resonance signals from overloading the delay chip.  If you shunt/short R11, the clipping of D3/D4 becomes "harder" and introduces more harmonic content.  If you want to experiment with more interesting high regeneration signals, solder in a wire bridge across R11 on the copper side of the PCB, turn up VR5 a bit higher (VR5 is normally set so that turning up the RES control all the way puts you just below the point of oscillation).

d) C7 sets the lower bandwidth point (bass rolloff) of the regeneration signal.  If you make it smaller in value, this will make high regen/res settings sound less metallic.  A value of .01uf might be a good place to start.

e)  The depth contol (VR2) adjusts the balance of voltages coming from the LFO and the Manual control to drive the clock (IC4).  VR7 is used to adjust or fine tune the delay time by adding (or maybe subtracting) a small DC voltage on top of whatever comes through VR2/R48.  C30 sets the delay range of the clock circuit.  Values larger than 47pf will set the minimum delay time much longer.  Smaller values will reduce the minimum delay time.  You can change the sound of the pedal by changing the range of delays it can produce.  Try a cap of 39pf and see if you like it.  If there are problems with the sweep, you may be able to fix them with VR7.  Alternatively, if you are able to find an MN3209 chip somewhere, you can take the MN3207 out and replace it with the MN3209 for shorter (X/4) delay times and more of a "jet plane" sound.

f) Vibrato is created when you use ONLY the delay signal, and leave out the clean signal.  If you lift one end of R28, that will prevent the clean signal from being mixed in with the delay signal, and give vibrato.  Unfortunately, because of how bypass is done in this pedal, this means that when you try to bypass the pedal, there will be NO sound coming out.  There is a solution to this problem shown here: http://home.earthlink.net/~ehansen3/diy/ce2.htm

[Guga Ramone]

  Thank you guys!! VERY MUCH!!!!    

[nelson]

I have done mod D, Highly recommended, thanks Mark.

[Steben]

Shorter delay -> more flanging, less chorus right?

I think I gonna stick a switch in that adds a cap in parallel, reducing the delay (flange mode)