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StratoSphere
Double Platinum Member
Canada
2232 Posts |
 Posted - 09/14/2006 : 02:13:34
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i just got a Bf-2 real cheap knowing it was not working.
when i turn the manual depth and res knobs, i can hear the sound changing, but i get nothing when i twist "rate." i opened it up to see if theres any wires out of place, and compared it to my HF-2..(turned out to be almost exactly the same insides). but everything seems to be ok. anyone have any suggestions as to what is causing the problem. Thanks in advance. |
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starr36
Platinum Member
Canada
1172 Posts |
Posted - 09/14/2006 : 03:06:48
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absolutely get out a big magnifying glass and inspect for cold solder joints.
try and figure out what works the way its supposed and what doesnot work.
get a copy of the Boss service notes and trace the circuits look for cooked or physcially broken components.
Based on what works, try and figure out what components are common to working sounds and other paths that are common to non-working sounds.
i got a DC-3 that I was not told did not work properly and I found that one of the pots (the depth pot) had cold solder joints. a 5 minute fix after lots of esamination.
good luck |
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starr36
Platinum Member
Canada
1172 Posts |
Posted - 09/14/2006 : 03:08:49
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if the rate control is the only one that does NOT work, check everything connected to the rate control. check for continuity of the rate pot.
this is actually pretty esasy to debug if ONLY the rate control does not work. gives you a big clue to where teh problem is. |
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 09/14/2006 : 03:31:34
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thanks for the info Starr. i will look into it
im 100% sure its the rate knob. everything else works like it should. by "cold" joint i take it that you mean that its just old solder? what do you recomend soldering with..all i have is a big ass Weller solder gun and i heard that cooking wires by accident is a big problem.
i noticed for both the BF-2 and HF-2. there are only 2 wires attached to the rate pot as opposed to 3 wires per pot on the three other knobs. any other ideas? keep em coming  |
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starr36
Platinum Member
Canada
1172 Posts |
Posted - 09/14/2006 : 03:58:08
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ok, thats easy.
a cold solder joint is one that is broken inside or poor connectivy because it was improperly soldered originally.
all you need to do is reheat the joints and add a little fresh solder if needed. but you really should be using a pencil-type soldering iron. Even a hobby one would work. I recall you work with sheet metal, one of your buddies at work should be able to spot you one for the weekend.
get an old digital alarm clock and just pracice reheading solder joints, so you get the "Feel" of it so you wont' trash your nice BF2, any joints that don't look shiny silver are suspect. |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/14/2006 : 06:16:43
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Here's the schematic:
http://www.freeinfosociety.com/electronics/schemview.php?id=117
Looks like your trouble is in the vicinity of IC5, which is a TL022CP. This has the "standard" 8-pin dusl op-amp DIP layout, by the way, so any RC4558, LM1458 or LF353 you have laying around will substitute -- and since it's operating as an LFO and no audio signal is passing through, specs probably aren't all that critical. I'd still probably go with an exact replacement for the permanent repair, though, to keep the circuit original if nothing else.
Looks to me that Q8 generates the clock for the BBD driver, and the action of IC5 (whatever it is, probably some sort of sawtooth action) tweaks the frequency up and down a bit. If you were to scope the clock signal with the flanger generating a "jet plane" effect, you'd see the clock frequency increasing as the sound "rises" and decreasing as it "falls", that sort of Doppler-ish pitch bending you hear. At least it's like that in the Electric Mistress circuit.
So if you Manual and Depth controls are working, that suggests to me that you've got clocking. And Resonance is in a completely different part of the circuit (that's feedback in the wet signal path), so if it's just a Rate issue I'd probably replace IC5 to see if that brings it back to life. Doesn't really look like there's all that much else in the LFO circuit that could have failed on you (passive components in low voltage/current circuits rarely ever do). This is also assuming you've checked out all of the mechanical stuff like broken connections and/or cold solder joints.
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Edited by - stahlhart on 09/14/2006 06:29:53 |
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 09/14/2006 : 13:25:57
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thanks stahlhart. nice link. if the resoldering doesnt work, i will look into this.
starr im sure i can borrow one off a friend or coworker. i have soldering experience, but just not this tight with that many wires in the way
Thanks for the help
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/14/2006 : 21:53:47
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If it does turn out to be IC5, you'll probably want to install a socket for the replacement -- you can avoid applying heat to the new one that way.
Desoldering braid will be an absolute must if you work on the board. Also helpful, for the sake of neatness, will be some Q-Tips and annhydrous alcohol to clean up the excess flux from both the desoldering as well as the soldering steps. If you clean up the flux left behind and solder neatly, you can end up with a virtually invisible repair.
In the U.S., Radio Shack sells the alcohol as "professional tape head cleaner" (as opposed to the cheap color-dyed water-based alcohol cleaner). It costs a bit more, but it evaporates more cleanly, without leaving residue behind, and is a good solvent for the rosin flux in solder.
Good luck...
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 09/16/2006 : 07:10:10
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well, i checked all of the joints and resoldered the 2 wires going to the rate pot at both ends. still no good. guess its something to do with a component on the board.....and i know nothing about that stuff. although i gave it a lookover, and nothing is physically broken. |
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 09/16/2006 : 07:12:50
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| wait. could it be the actual pot thats no good? |
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stahlhart
Platinum Member
1318 Posts |
Posted - 09/16/2006 : 15:39:43
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Extremely unlikely unless there's some sort of visible damage to it, but I suppose that anything is possible.
You'd need an ohmmeter to verify it: leads across the two outer lugs will give you the full resistance value, and across the center lug and either of the two outer lugs you should see resistance change from zero ohms to full resistance, the rate of change being dependent on what the taper is (linear, logarithmic, etc.), as the control shaft is rotated.
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 10/05/2006 : 02:52:41
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well i finally ordered some ICs and a new soldering iron from Smallbear. ill let ya know how it turns out.   |
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 10/13/2006 : 20:12:25
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| i replaced the IC5 chip with the LM chip and its still the same. it kinda sounds like a sitar or something. i dont know. oh well |
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stahlhart
Platinum Member
1318 Posts |
Posted - 10/14/2006 : 04:30:32
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Bummer. I thought for sure that would be it... sorry.
If you'd like me to put a 'scope on it to track down where the trouble might be, I'd be willing to give it a shot -- let me know.
I also have the service manual for the BF-2, which has alignment instructions and waveform illustrations for test points -- let me know if you'd like a copy.
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StratoSphere
Double Platinum Member
Canada
2232 Posts |
Posted - 10/14/2006 : 07:04:20
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| no prob. i decided to take off the whole board. im currently putting it back together. on wire 10 of 18. just taking a break |
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BF-2 help
