Boss BF-2 Flanger not working, need help.

[2decopas]

Hello!

This is my first post here, although I usually come and read your topics and contributions. A lot of priceless information can be always found in this site. Thank you so much.

I have a problem with my old Boss Flanger BF-2, MIJ, green label. No mods. I bought it new in 1990, and now has stopped working.

The dry signal is always there, when the unit is switched on, or switched off.  But the wet signal is not present when you switch on the flanger. No hum, or any kind of noise. Just the dry signal, without any audible difference between both modes.

The led brights when the flanger is supposedly engaged, but only if I use a battery to power the pedal. If I use the Boss ACA-220, the led will never bright.
The dry signal is always present, both with the battery and the ACA-220.
The ACA-220 was tested and works fine.   

I wonder if there is a way to fix it, perhaps somebody knows what is wrong and figures the way to repair the pedal. Any feedback would be appreciated.

Thanks in advance,

  Manuel

[Scruffie]

I would check the voltages of Q6 in the on and off state https://www.hobby-hour.com/electronics/s/schematics/boss-bf2-flanger-schematic.gif

And failing that, take voltages of IC2 & 3 and Q2 & 3, an audio probe would be a good step too.

[ElectricDruid]

Welcome!

Why would the LED not light with the ACA-220 adaptor? I don't see the reason but this strikes me as significant somehow.

It doesn't look to me from the schematic like the BF-2 was designed for an unregulated adaptor (no resistor in series). I'd have thought you needed the Boss PSA regulated adaptor (or an equivalent). Are you sure it works with the ACA-220?

[2decopas]

Hi Scruffie,

I will do that and let you know the results.

Thank you so much!

[2decopas]

Electricdruid,

that confuses me too.

I have checked again the ACA-220, with another Boss pedal, the Limiter LM-2, and works fine.

By the other hand,the BF-2 needs an ACA-220. Perhaps because is and old unit.

[ElectricDruid]

Ok, just checking. That seems pretty conclusive.

But it also leaves the question unanswered: why would the LED work with battery power and not with the adaptor?

From my understanding, the unregulated adaptors provide *more* voltage than a battery, more like 12V rather than 9V. Obviously, for a lot of pedal designs, running on 12V not 9V is no problem at all, and that would be the same for an LED with a suitable series resistor.

So what's going on? why does one work and the other not?

I realise this is a "side point" to the original problem, but I've got a nagging feeling it's like one of those Agatha Christie murder mysteries where you eventually discover that the aardvark under the billiard table was the key to the whole thing all along...

T.

[2decopas]

Hi,

the BF-2 is working again!  The problem was a shortcircuit in C40.  After replacing it, the flanger came to life.
It was so difficult to find. A friend of mine helped me because I was not able to fix the pedal by myself.


Thank you so much for your interest and your help!