Hello,
I have a bf-2 with a broken res knob. The whole post is broken off and I'm looking for a replacement pot.
I found the schematic online and it looks like the pot is a 50KC. My question is what type of pot is this?
http://www.freeinfosociety.com/electronics/schematics/audio/pictures/bossbf2.gif
rk
The C refers to the taper of the pot. Theres A (audio), B (Linear), and C (reverse Audio) taper, plus lots of other crazy specialized tapers, but these are the main ones. The pot you need is probably the tiny 9mm alpha brand, which would definately be a special order thing. If you have any other boss pedals to pick apart you could take the shaft from a different pot, and take apart the busted one to replace the broken shaft.
Theres a good article at geofex.com (http://geofex.com) called "the secret life of pots" its under Tech tips I think.
It has lots of ideas how to fix pots, clean em, and fake them with whats around.
If you can get a linear pot 50K to fit, I'd use that.
The action will be cramped at one end, but you can live with it.
........or more likely a 47k linear pot
Stephen
How about a 47k Log pot wired backwards ?
The pots in the BF-2 are not the super-tiny 9mm ones, they are 16mm that you can get from Smallbear. Only problem, smallbear only has the smooth shaft pots IIRC. May have to look around at Mouser to get the 16mm pots with the split-knurled shaft pots.
At least, thats the way they are in my BF-2. Mine are not board mount, they simply mount straight to the chassis and have the wires coming off of them.
That being said, if anyone knows where I could order the 9mm pots with the split-knurled shaft, I'd appreciate it. Need to rehab my DF-2 pedal. I looked at mouser and didn't find them.
As with taper of any pot, the ideal taper depends on what you need the control to do, and where you would like to have the greatest capacity to dial in small distinctions. Quite frankly, you can probably stick a linear taper pot in there and it will be fine. It will certainly *work*. The only difference may be how "twitchy" the control is at one end of its range or the other.
Yes, in theory, you could install a normal log taper and reverse wire it. But since the pot is soldered to the board and since the lugs are already pretty much spoken for in terms of which is input and ground, the reverse wiring would be tricky to install. My vote is for sticking a linear taper pot in there, living with it for a bit and seeing if it is too terrible to live with.
The article in Home & Studio Recording for building a gate included some sharp circuitry for changing the law of a pot which I'll post if it is any help.
Stephen
Here it is
http://img.photobucket.com/albums/v517/uncle_boko/potlaw.jpg
An OCR extract from the article is thus:
"The Attack pot of Channel I also provides for very long Attack times for fade-in and is required to operate over six decades of current while maintaining a sensible knob calibration. This is not easy! Transistor Q5 is strapped across RV3a and is itself controlled by RV3b. As RV3a is rotated towards the low resistance end Q5 is progessively turned on reducing further the resistance of RV3a. In this way the ordinary log law of RV3a is converted into a 'super-log' law - at mid position the resistance is only 2% of maximum instead of the usual 10%."
Clever stuff is OCR! I would imagine this could be adapted to perform any log law required.
Stephen
Are there some versions with board mount pots? My BF-2 does not have them. Straight mounted to chassis with solder lugs. If he has the same type as mine, he could just wire a straight log pot backwards.
Quote from: PenPen on November 06, 2005, 01:55:15 PM
Are there some versions with board mount pots? My BF-2 does not have them. Straight mounted to chassis with solder lugs. If he has the same type as mine, he could just wire a straight log pot backwards.
Thank you.
I had the same problem with my BF-2 and on a lark, called up Roland/Boss to see if I could buy a replacement part. I did, but it was $7.00 for the pot plus shipping, if I remember correctly. I don't know if they will sell those anymore to us Joe Schmoes.
The pots are wired on my bf-2. I have decided to try some j-b weld, but im not sure how long that will last. I cut the post off another pot and glued it to the stub. When this snaps off ill try a more permanet fix. :icon_frown: Thanks.