Tracing and modifying a Langtronics Bone Collector

[moid]

Hello everyone

I'm wondering if anyone could help / offer sympathy / prayers for my darkened soul as appropriate. I'm trying to trace my Langtronics Bone Collector so that I can build a new version of it with more controls and the ability to blend dry audio with the circuit (it's a fierce squealy synthy fuzz thing, based on Tim Escobedo's Uglyface schematic, but with a lot more parts). The original pedal was covered in goop (glue gun plastic / hot glue) which I've scraped away mostly and I've tried to trace the circuit and have drawn a schematic below. I've tried to build this on breadboard twice now, first time did nothing, the current version (which had 5 extra parts I forgot in version 1, who would've thought they'd be useful?) passes a mild version of the astonishing noise the original is capable of and the potentiometers in the circuit do nothing (well they must do something, since removing them kills the audio, but turning them has no effect on the sound). I made a couple of substitutes due to lack of parts (the 82pF cap is a 100pF on my breadboard and the 120r resistor is a 150r on my board)

When looking at the photos / my drawings it's highly likely that I've drawn in resistors of the wrong values - one of the many joys of being colour blind is that I've had to take photos of the PCB and then use a colour picker tool in Photoshop to work out what the colours are on the resistor, and it's quite likely that I've got them wrong, which might be the reason the circuit isn't behaving itself.  Mr Duck from down under has offered kindly to look at my photos of the resistors but I'm sure he won't mind if anyone else wants to play spot the resistor

Here's my schematic and a drawing of the backside of the PCB (components reversed because they are on the other side of the PCB)


Here's a photo with annotations of the topside of the PCB


Another photo of two resistors that are hard to see in the above photo


photo of the back of the PCB


trimpot that I'm not sure what value it is


Thanks very much for any help!

[duck_arse]

clr appears to be 2k2. alll other resistor values appear korreckt. can you hold the board up to a strong light so we can see shadows of copper traces please - there is something screwy with the R8//R11 connections not making itself apparent on the copper.

you could use TL072 as buffer with a little gain, followed by another gain stage feeding a rectifier, or something like that, to replace the lm386.

your meter should expose the trimpot value, and which end is ldr.

[moid]

Eagle eyes, that's what you've got, not duck eyes The backlit photo (not great, I don't think my phone is good for this sort of photography) shows a trace link between R8/R11 and pin 6 of the TL072!!!



Thanks for identifying the CLR, the goop was making it hard to get some colour values that I could guess correctly.

Regarding the handmade vactrol; how do I determine which end is the LED and which is the LDR? I put my DMM on all the leads with music playing through the pedal and both ends of the tube flicker on and off quickly, while meter readings on all the four legs tend to jump around constantly... I think that the tube is brightest at the end facing the NE555 which implies that in my diagram the vactrol is the wrong way around.

The trimpot does indeed read as 1.2K(checked with the DMM). I'm currently using a 1K pot, presumably that shouldn't have a massive difference of effect?

I'll ask you about the comments on the TL072 later, I'm off to fix the gap between R8 and R11 to see if any magic happens!

[moid]

OK I now have more volume and distortion but no control over it, and bizarrely disconnecting either potentiometer still allows music through the circuit (unless I remove the final pot wiper connector to out of course), so something is shorting the music through ground and into the socket? Who knows... anyway while re arranging the components I have discovered something that almost made me cry... I've swapped the NE555 for the TL072 on the breadboard... two thirds of my connections are therefore probably rubbish and it's a small miracle that anything is actually happening at all

I think I will need some sleep before I can begin the miserable process of laying this circuit out again... how did John Cleese so eloquently put it? "It's not the despair, I can take the despair; it's the hope I can't stand"


Edit: if the LED side of the vactrol now goes into pins 6 and 7 of the NE555, which pin takes the positive leg of the LED? Any guesses? I'm guessing at positive leg goes to pin 7 (discharge) and negative leg goes to pin 6 (Threshold). Feel free to tell me I'm wrong.

[duck_arse]

well your circuit matches the board as you have presented it, but that circuit seems to be using the ldr in a different manner to the uglyface.

[smaller images, maybe? it's better to have the connecting lines on screen instead of whitespace and scroll. and when drawing a box-type thing, like the 555, it is nice to include some hint to the pin functions. tr for trigger, out for output, things like that. same goes for the 386, draw it as a triangle to indicate its function, then add the (+)(-) inputs so's we know what those parts are connecting to. once you indicate the pins by name and number, they can be moved about "the box" to clarify/ease the connections. and the dual opamp is two opamps, not a box.]

[anotherjim]

It would be logical for the 386 to be driving the vactrol LED. It would make no sense for the 386 pre-amp to be driving the LDR.

Beware some of the "boutique" designs can contain bad practice and superfluous "copy catch" components. The 386 can end up driving the LED directly with no CLR present if the sensitivity pot is max. I don't know if that vactrol contains an integral LED CLR. The 2.2uF cap in between is wrong polarity on the scheme; should be  negative to the pot. There appear to be extra 1M and 56k resistors (R8, R11) on the reference voltage divider that can't be doing much of consequence IF they really are placed as drawn.

[moid]

well your circuit matches the board as you have presented it, but that circuit seems to be using the ldr in a different manner to the uglyface.

[smaller images, maybe? it's better to have the connecting lines on screen instead of whitespace and scroll. and when drawing a box-type thing, like the 555, it is nice to include some hint to the pin functions. tr for trigger, out for output, things like that. same goes for the 386, draw it as a triangle to indicate its function, then add the (+)(-) inputs so's we know what those parts are connecting to. once you indicate the pins by name and number, they can be moved about "the box" to clarify/ease the connections. and the dual opamp is two opamps, not a box.]

OK duck, I will try to draw things smaller soon... I go large so that my eyes can actually see what I'm drawing (my eyesight is rather poor, and only one eye can actually focus properly, the other one blurs everything in a mostly horizontal direction ) I sense another expensive visit to the opticians soon.

Well I rebuilt the entire circuit tonight, found some extra components that weren't attached, added a few I had missed... but now I have a reasonably pleasant fuzz that sputters a bit as it decays, but it's not that loud (compared to how deafeningly loud the original pedal is) and there's no synth noises. The volume pot (the log 100K one) now makes the circuit a bit louder at one end of the sweep, but not a huge volume jump. The 1K pot makes a  lot of weird crackles if you turn it, but it doesn't do much else. Maybe I need to find a 1.2K pot?

I'm wondering about removing the NSL32 I put in and sticking a super bright white LED and an LDR in it's place like the original - perhaps the issue is the NSL32 not being in the same brightness / resistance range as the one on the original pedal. I think the 4K7 (R3) is the CLR for that LED, which means the positive leg of the LED would connect with pin 7 of the NE555 as I've got it. Something to try once I've had some sleep. Thanks for your suggestions, I'll re draw soon.

Hmmm I agree about labelling the ICs, that's a good point. Why are opamps triangles? They look like boxes to me (they even feel like boxes, so I know that's not my eyesight!). Boxes make more sense to me to draw, but I shall bow to your capricious whims and go to sharpen my pencil... OK, push the mouse about. I'll make updates tomorrow, it's too late now and I think I need to sleep without breaking anything new (I managed to break the original pedal this evening; it's full of solid core wire which is really brittle as I've discovered - but at least I soldered it back together again and it still works!)

[moid]

It would be logical for the 386 to be driving the vactrol LED. It would make no sense for the 386 pre-amp to be driving the LDR.

Beware some of the "boutique" designs can contain bad practice and superfluous "copy catch" components. The 386 can end up driving the LED directly with no CLR present if the sensitivity pot is max. I don't know if that vactrol contains an integral LED CLR. The 2.2uF cap in between is wrong polarity on the scheme; should be  negative to the pot. There appear to be extra 1M and 56k resistors (R8, R11) on the reference voltage divider that can't be doing much of consequence IF they really are placed as drawn.

Hi anotherjim - thanks very much... sounds like I have the NSL32 in back to front then! I will swap that about tomorrow. I don't know if the vactrol contains a CLR of its own - it's pretty small, but who knows? It's gooped up with hot glue; I had a go at cutting some of it out, but it fills the entire tube of the vactrol and it's not shifting Well spotted on the 2.2uF cap, I've swapped that around now. I will double check R8 and R11, but yes they do seem to be where I've drawn them. I don't know enough to tell if that's wrong or not, like you say this might not be the best way to construct the circuit.

[duck_arse]

when I say blah blah do it like this - just ignore me. develop a circuit drawing style that suits you, makes sense to you, that you can read.

opamp triangles are representative of the IC internals, so you know at a glance you have some amplifiying going on, rather than some boxing going on. and you can say/see inverting, or non-inverting buffering, like that.

use a 1k trimpot, you'll be hard pressed to find a 1k2. you can substitute a pot - 250k + 47k resistor in series - for the ldr to test the function of the 555. and an external led should indicate the 386 functioning. as the output pot dangles from the 555 output pin, making about 7V squarewaves, you should have a lot of volume on tap.

[duck_arse]

moids! I've done a sloppy redraw from your copper-side, with no values and wrong part numbers. the connections should be correct, but I'm not 100% about the R2//R3 connections (my numbers). schem attached.


anybody looking it over - let me know for corrections and errors, please.

[edit :] why does it have two pulldown resistors, the 1M and the 10M? one of anotherjim's traps?

[moid]

Wow, thanks Duck! I've actually been re drawing my schematic to make it more 'normal' but got stuck at how to draw the TL072 because I couldn't figure out which triangle got which of pins 4 and 8 - so you don't mention them at all on your schematic, is this because it's obvious to most people that a TL072 has power going to pin 8 and pin 4 goes to ground?

In other news I discovered that I had not connected the 22uF capacitor after the 1n4001 Diode to the vactrol (LED side)... doing that gave me a decent fuzz, quite powerful and (I think) is generating some octave down sound, kind of synthy. However the potentiometers do nothing at all which is weird. I tried swapping the Vactrol out for an LED going to pins 6 and 7 of the NE 555 and a 5K - 500K LDR to connect elsewhere in the circuit. The LED will only very occasionally flicker slightly (I tried white and red LEDs). If I bridge pins 5 and 6 of the NE 555 then the LED glows constantly. Duck, I think you may have copied my mistake from my schematic there - look at the drawing of the back of the PCB and that capacitor connects to the vactrol and not to ground.

No sign of the synth noises of the original pedal, apart from at one point last night when it emitted a furious high pitch that really hurt my ears

The original pedal's vactrol only lights up when the guitar is playing - not sure if that's a useful clue or not?

Measuring the NE555 at pin 6 I get 0.7v DC, but if I strum the guitar this jumps to 4v and then decays. Pin 7 is constantly reporting 9.12v.

Maybe the NE555 is busted or suffering from whatever the reason you warned me to avoid using them (at the weekend I'll try to order some new parts and get the better 555 chip I mentioned). I do still need to find a 120ohms resistor and an 82pF capacitor, perhaps the lack of these correct components has an effect.

To me it looks like R3 should have a capacitor after it before it goes to ground - in the drawing I made of the back of the PCB the 56K resistor connects to a 10uF before it goes to ground (or does that not happen?)

Thanks for your help!

[duck_arse]

today I was farnargling some papers, and the mxr blue box circuit appeared. lo! and behold, guess what the bonecrusher is based on? well, at least the front end, up to the 555. only a few value changes I could see.

but the bonecrunch at hand. the LM386 is used to drive the led with the audio input, so should only light when signal applied. the light is coupled to the ldr in the 555 timing string, so as the led brights, the ldr will lower its resistance, and the timer will - erm, either run faster or decrease its "off" (or on, can't remember) time. a form of envelope control. the tl072 provides a whack load of gain to a comparator wired opamp, which goes on or off at a great rate, feeding the reset pin of the 555. the exact operation of the 555 is currently beyond me, but it will be outputing squarewaves at pin 3, fed to the level pot, complete with the blue box "tone cap", the 10nF.

so, now my dia - I redrew the LM386 for my own porpoises, and left off the power pins. the lm386 power pin connects to the 1N4001 and (my) C12, nothing else I can see connects to that diode. this is strange, but workable, in that it will protect the 386 from reverse polarity supply, but not the rest of the circuit. oh, well.

the TL072 power pins are there, but are not so clearly marked. as for your cap and led connections, you have me confused. it looks to me as tho the led hangs straight from the trimpot, and the trimmer hangs off the 386 via a cap. which seems sane.

you should not be connecting the LED to the 555 at all. what I've shown as IC1B is the comparator, and I had the bluebox circuit on the BB recently - this section was giving me trouble cause it wouldn't stop creating fluff [it's not fuzz, because it is not useful, so "fluff"], I think bonesman might have 'cured' that problem by pulling one leg (-) of the comp high (to V+) via my R2.

any clearer now?

[edit :]  while I think of it, the 555 is as near indestructable a chip as you could want. shoving 9V up its jaxy might finish it off, but if you haven't done that, carry on. and in this circuit, as you are taking the output from the 555, the ugly switching spikes they produce (that the cmos version had designed out) probably won't matter.

[moid]

I drew a new picture



And with any luck it's smaller, displays easily here and has the right opamp symbols (I'm learning!). I found your power symbols for the TL072 in the end, but I've attached them to the opamps in my drawing to help me remember where things go.

Now, are you sitting comfortably? Fancy a chuckle? Guess who didn't connect the power and ground of his breadboard from the top half of the board to the bottom half of the breadboard? Guess which part of the circuit was in that lower half? Yes, it was the TL072. @#$% me did I jump when I strummed the guitar having the had the amp volume on about 8 (so I could hear anything coming out of the circuit) and my headphones were plugged in because everyone else is asleep. No, no, I never wanted to hear anything over 3000Hz anyway. I seem to be hearing a strange high pitch drone signal... the aliens, they are signalling to me!

So... the volume pot now works I removed the Vactrol because it did bugger all (maybe I killed it earlier? I did shove the damn thing in every possible hole to see if something would happen... hmmm don't try that at home kids!) Anyway, I placed a 5K - 500K LDR on pins 6 and 7 of the NE555. I stuck a White LED with the long leg to the wiper of the 1K pot (sensitivity) and the short leg to ground. I now get some synthy squarewave noises, but the LED will not light up. I've tested it on its own (with a 2.2K resistor) and it lights up beautifully, but not here. As you pointed out the LED will control the synth sound cutting in and out, so at the moment it is just fading in and out with the audio, but on the original pedal it only kicks in when the loudest notes play. Adjusting the Sensitivity pot didn't do much either, I tried a larger pot (2K lin) and that made no difference- the LED refuses to come on. That looks like the last thing to fix - any guesses?

Thanks again

[anotherjim]

LED with a higher forward voltage than the original vactrol will have weaker performance. LDR in the open suffers from ambient light already operating it. In a vactrol, the close coupling between LDR and LED inside the dark case means that useful LED light output can be so slight it's invisible out in the open.

You can test the vactrol same as you tested a LED, only instead of looking for LED light, measure the change in LDR resistance with your DMM when the LED should be lit. Don't forget to use a CLR, 2k2 should be ok.

Looking at NSL32 datasheet shows it does NOT have an integral CLR for the LED, so there has been plenty of opportunity for it to be blown by excessive current. Even connected in the circuit as shown, the 386 is quite capable of delivering damaging current into the LED with only the impedance of that 2.2uF cap to limit it.

[duck_arse]

if you were wanting a little more maddness, you might try connecting a cap (?100nF? for a start) between the LM386 output pin and the 555 control voltage pin. then your osc rate should warble up or down (I don't know, maybe both, alternately) with input signal level. well, massively distorted by the 386, but still.

diagramming - becomes neater if you take a point, like the junction of R6//R9//10uF and call it V/2, or Vref, or Vcc/2, or bias. then you can use shorthand, like an arrowhead, at each point connected to "bias", and you don't then need lines running full length of the dia. this is how/why we use the ground symbol (and something like V+ arrow), to reduce lines.

[moid]

See Igor, it moves!

Thanks very much chaps we have a winner anotherjim was right, I'd fried my NSL32s. Both of them. Ouch. Plus a couple of red LEDs, but I have plenty of those so not so ouch.

The lack of illumination of the LED was caused by weak connections on the cables I'm using to connect the board and its components together (some dodgy male to female connectors and a strip in the breadboard that doesn't seem to conduct electricity). The circuit needs bright light though. I removed the suggested 2k2 resistor and just took the power from the 2.2uF from pin 5 of the LM386 to make it brighter. Could I run two LEDs this way, for extra brightness? Because when I shine a torch on the LDR (yes I'm doing this in the dark so I can check the LED is working) the synth noise is even greater and wilder! Maybe this should be on a switch to add more squeals?

Duck, that cap idea is quite genius 100nF and lower didn't do much (slight high pitch edge), at 1uF things start to get interesting, there's a slight %^&*ed wah edge to the sound, plus increased arpeggiation of the circuit, but with some constant noise on the bridge and neck pickups - switching to the mid pickup removes this. Me being me, I had to go higher! 10uF is really wild, a strong wah effect on the synth sounds, but constant noise on all pickups (maybe this will be better once everything is soldered?) I'll keep it, but if there was a way to tame the noise, then it would be cool to hear it thanks. I think I'll use a DP3T switch for the caps so I can have original (no cap), 1uF and 10uF as options.

Would the synth be wilder If I put a 10uF between pins 1 and 8 of it (the data sheet seems to think the output will become 42dB!) I might have to make that a switched in option as well.

I have changed the sensitivity pot to 2K - the synth sound is larger with this pot than the 1K  I was using... I might try 5K tomorrow? Is that likely to nuke the LED? I'm asking because I only have two ultrabright LEDs left (time to buy some more). When the pot is set to off it turns off the synth sounds and seems to make the arpeggiation of the circuit stronger. As I turn it on I get more and more synth sound, although there's not a huge range, so I can see why the original designer made this as a trimpot inside set to maximum (maybe he could've just used a fixed resistor?)

Time to start thinking of mods... I think I won't upset the circuit as it is to make a clean blend, I'll use the Mr Black Tiger Boost schematic and then feed the two signals together with a blend knob.

Thanks again, I'm happy... but need some sleep. Bedtime for me.

[anotherjim]

Totally changed edit!

Maybe better yet, actually find out what is the smallest CLR for the highest likely voltage in the circuit that could cause a damaging current.
NSL32 max LED current is 40mA. Being a diode, it only reacts to half the voltage swing of the audio signal. As drawn, that is the positive half. The coupling capacitor removes the 386 output 4.5v DC bias meaning the positive swing seen by the LED is 0v to nearly 4.5v. The LED has a Vf of 2v, so only 2.5v needs to be absorbed by the CLR. Ohms law tells you that R=V/I so 2.5/.04 and nearest standard value R for that is 68R.
40mA is a huge current for the job a vactrol LED needs to do, so I say we can raise the 68R somewhat and also protect against the worst fault state it might encounter. I'd say the worst state is a short to the +9v supply. Easily encountered on the breadboard or due to assembly error.
Calculating again for the 9v case with 7v to lose on the CLR is 7/.04 is close to a 180R value.

[duck_arse]

for moids eyes ONLY - http://i.imgur.com/PyToWOn.png

if you, moids, have a butchers at the circuit linked, find IC4 where it says "CV mod". the mod is next the title box, and shows how to wire an LDR to the CV input via a switch. (let's ignore SW7 for the moment, connect the ldr straight to pin 5.) now when you shine light on that ldr, one position will make faster, the other will make slower. from memory. the lisght can come from a led driven by the lm386, or from ambient with your hand waving, whatever.

run out of ldr's? get those bung nsl's you kilt, and carefully cut-off the led end. should be a semi-light-shielded ldr in there somewhere.

pins 1 and 8 are connected together by a wire. you won't get any more gain by sticking a cap in there instead. it might make it less bass responsive or something. and if you are going higher than the 1k trimpot, make sure you CLR.

I SAID - how are the ears?

[moid]

Totally changed edit!

Maybe better yet, actually find out what is the smallest CLR for the highest likely voltage in the circuit that could cause a damaging current.
NSL32 max LED current is 40mA. Being a diode, it only reacts to half the voltage swing of the audio signal. As drawn, that is the positive half. The coupling capacitor removes the 386 output 4.5v DC bias meaning the positive swing seen by the LED is 0v to nearly 4.5v. The LED has a Vf of 2v, so only 2.5v needs to be absorbed by the CLR. Ohms law tells you that R=V/I so 2.5/.04 and nearest standard value R for that is 68R.
40mA is a huge current for the job a vactrol LED needs to do, so I say we can raise the 68R somewhat and also protect against the worst fault state it might encounter. I'd say the worst state is a short to the +9v supply. Easily encountered on the breadboard or due to assembly error.
Calculating again for the 9v case with 7v to lose on the CLR is 7/.04 is close to a 180R value.

Thanks very much - I missed your first edit, but I'll add a 180r resistor after the 2.2uF cap now. I'm going to place an order for parts tonight so that can be on it! I'm not going to use an NSL32 now, I got much better results with the ultra bright white LED and LDR (mainly because I hadn't fried those) but also because I can see they are actually working, which I couldn't see so easily with an NSL32.

[moid]

for moids eyes ONLY - http://i.imgur.com/PyToWOn.png

Yikes, that looks fiercesome! I suspect that it's powerful enough to become sentient and might chase the neighbourhood cats up a tree while barking in a metallic ring modulated sort of fashion! Is this the schematic equivalent of What The Butler Saw? Nobody else look, I'm admiring the poetic form and aesthetic set of massive.... resistors on that circuit. This could be art - I can't understand it; and that's my usual way of deciding whether something is art or not

if you, moids, have a butchers at the circuit linked, find IC4 where it says "CV mod". the mod is next the title box, and shows how to wire an LDR to the CV input via a switch. (let's ignore SW7 for the moment, connect the ldr straight to pin 5.) now when you shine light on that ldr, one position will make faster, the other will make slower. from memory. the lisght can come from a led driven by the lm386, or from ambient with your hand waving, whatever.

Okay... so I should use this LDR setup instead of the 1uF or 10uF capacitor idea you posted before (it makes a pretty good noise though... hmmm I could probably have both though! As long as they are on separate switches I might as well! I'd probably use the light inside the box itself, ambient light LDRs seem likely to make annoying constant noise when you don't want them to. One question - what is the symbol above the switch itself - it looks a bit like a letter T with  a handle on the left side of it - I can see it on other switches; does it denote a SPDT or something else? By the way (in case it's important) IC1A is missing some text saying what it is in your schematic. See - I do look sometimes

I think I'll try multiple LEDs for extra brightness though to see what that gets me.

run out of ldr's? get those bung nsl's you kilt, and carefully cut-off the led end. should be a semi-light-shielded ldr in there somewhere.

Now that's just plain cunning - and there I was, about to snip the legs off them to use as rather long jumpers (as I sometimes have the need). Time to find me a knife and start cutting.

pins 1 and 8 are connected together by a wire. you won't get any more gain by sticking a cap in there instead. it might make it less bass responsive or something. and if you are going higher than the 1k trimpot, make sure you CLR.

I was looking at the top of page 10 of the datasheet for the LM386 and it shows if you put a 10uF cap between pins 1 and 8 you get a 40dB boost, if there is no cap you get 20dB as described at the bottom of page 8. http://www.ti.com/lit/ds/symlink/lm386.pdf Have I got the wrong end of the stick again?  I must stop grabbing the end that's on fire... I might try it just to see what happens as soon as it gets dark here!

I SAID - how are the ears?

Half Past Four! You don't have to shout so loud, I'm not deaf you know As long as everyone speaks through the medium of whalesong I can hear them perfectly... luckily the wind sound in my ears seems to have dissipated, thanks!