Build Your Own Clone Message Board

Hi everyone,
I'm having a strange issue w/ my stereo flanger build. When switched on it only gives an oscillation/buzz that changes speed when I throw the differential switch (no output). That's the only response I get from anything (turning pots does nothing) was when checking it out using a flashlight I noticed that it made the noise change speed/frequency as I passed it over one part (center-left) of the circuit board!!??
I have a multimeter and patience but I do need to get it going asap as it's a build for a customer. I've checked solder joints and all the typical stuff. I do have a good bit of soldering experience as a luthier/guitar tech for 12 yrs.

It (along w/ ping pong delay) are being stuffed into an old banjolele (very adventurous customer!)!! I've had to wire the pots/led's to leads off the board so I can mount them on the rim of the instrument. I do plan to take pics tomorrow and I'll add them to this post then. I'll call it the "Flanjo-lay-le"!!

Thanks in advance!

Hi tonesville - welcome to the forum!

Yes, please post some pics, and triple check the IC's are in the right spot and orientation.

Also, you can compare voltage readings with the voltage chart posted in this thread: http://www.buildyourownclone.com/board/viewtopic.php?f=20&t=23517

Hi Morgan, Thanks for the quick reply. I've been trying to figure this out and called my dad (an electrician). He said that sometimes components could react to heat/cold when they're bad. I tried the flashlight again and pinpointed the culprit (D3). If I hit the solder joint the buzz/oscillation ramps up to a hi pitched whine (sounds cool-like a moog!) and back down as it cools! Does this sound like a bad diode to you? Still haven't setup my new camera yet but pics are incoming.

Thanks a lot

Your dad is right that heat or cold can effect electronic circuits and can sometimes be used to pinpoint faults, but in my experience it is an unreliable technique.

In this case what is far more likely to be happening is that transparent glass case diodes are mildly photo sensitive and it is the light from your torch that is changing the forward resistance of the diode. I think it is unlikely that there is anything wrong with the diode and it may be only very indirectly involved with the fault. D3 is part of the BBD clock circuit and you are probably hearing some clock break through on the audio output.

I hope you did not apply your solder and iron to the diode joints with the pedal switched on and plugged in.

The input signal must of course pass all the way through the pedal in order for it to flange. The input is split into two paths - the clean or dry path, which is the same as the input signal - and the slightly delayed path through the BBDs. When the two signals are mixed near the pedal output and the delay is swept, signal cancellation and reinforcement occurs in the mixed signal and you hear that as the flanging effect. If as you say you hear NONE of the input then the signal is not even making it through the clean path, a relatively simple part of the circuit. This makes it likely that the signal does not even get past the input buffer - IC1b or it may just not be making it through the output buffer IC5b.

There is one fly in the ointment - BYOC circuit diagrams often reverse the halves of dual op-amp with the result that the pin numbers on the circuit don't match the actual PCB layout, which makes it hard to debug. I seem to recall the flanger is one of those. I think Stephen has posted corrected schematics somewhere on this forum.

Hi Tark,
Thanks for taking the time. I don't think the part is photo-sensitive, just heat sensitive. The flashlight is how I stumbled upon the effect. I can touch the joint w/ my finger or breathe on it or (I did) touch my soldering iron to it and it'll take off. I started to measure the components even though I suppose things will be off w/ a bad part I got zero on r1 through r10 or so?! I'm gonna wait til tomorrow when the part store opens and get a new diode wired in and go through measuring the components. What is the risk in hitting a solder joint w/ power and output? I did just that! Hope I didn't fry anything.

Thanks a lot

Well the diode is much more likely to respond to the light from a flashlight than to heat from one. Touching the components or joints with your finger will certainly influence a circuit because you are varying the resistance and capacitance and injecting hum. Touching bits of the circuit while it is powered up and connected with a soldering iron is a BIG NO NO. This is because the soldering iron metal and tip is usually grounded, so you will short parts of the circuit to ground. This may cause currents to flow that are large enough to burn out components. If your soldering iron is not grounded you may have got away with it, but I really don't recommend it as a practice.

As far as the diode is concerned I strongly believe you are chasing the wrong cat up a tree. As I explained it is connected to the delay chip clock oscillator, which will change frequency if you mess around near the diode. This is entirely normal.

If I understand your description of the problem correctly you are not hearing any dry signal at the output. This is in no way connected with anything to do with the diode and is a much more basic problem than any clock oscillator breakthrough you may be hearing. If you are hearing dry signal then that probably limits faults to the delay side of things and it may be a clocking problem.

Measuring components like resistors while they are still soldered in to the circuit is often problematic because their apparent values are modified by the other components connected to them. One would usually try and measure voltages at certain critical points in the circuit and if that showed the DC conditions were OK, would then use an audio probe to trace audio signal through the circuit, rather than try measuring resistors in circuit.

Hi again Tark and thanks for your help. I do have output from a transducer pickup. Basically I'm going pickup to flanger to delay to jack. Both are getting power from batteries and I have to fly the pots/switches and jacks off the board to mount to the rim of this crazy amalgamation. I'll be cleaning up the wiring when I figure out how much length I need to mount the pots. I hope I'm not doing anything really stupid but I wouldn't be too surprised!





I think I'll start from the start and pickup a new diode tomorrow so that I know everything is fresh and then go through the components to measure. Then I can post any weirdness I find and all you great guys who are helping can have some info to go on.

I can't help with the flanger problem, but I do have one other thing for you to consider... if those are piezo pickups, they might require a very high impedance to function properly. You might want to consider placing a buffer before the first effect, designed to offer the max impedance possible. A simple op-amp configured as a voltage follower would work well.

Hi Cap'n,
The pickup isn't a piezo but it is a transducer. I know/sell the brand and they can be used w/o a preamp so the output is pretty high. I'm really not going nuts trying to achieve "tonal purity". This is literally a project w/ a producer who has $$ and a "let's make something crazy" attitude! He's also a drummer and I think it's gonna end up being a wacky rhythm device. The "Flange-o-delay-le" will take the music world by storm!

I apologise if I am speaking out of turn and I may be wrong, as you say you know the pickups you are using really well, but those pickups look like the K&K banjo twin, which K&K I believe describe as 'high ohmic' and recommend they see an input impedance of at least 1Megohm.

I suspect that all of the K&K pickup line are piezo. They are a bit vague in their descriptions and somettime say piezo and sometimes just transducer, but transducer means something that converts energy from one form to another. So a transducer may be a piezo transducer and I don't know of any really flat thin pickups that don't use the piezo principle in one form or another. As CP says, that type of pickup losses bass if it drives into too low an impedance. The input impedance of the BYOC Flanger is only 235Kohm.

The long leads you have to all the external components may cause you problems and if you are fitting all that stuff into a wooden shell you will need to add some copper tape screening and connect it to signal ground.

If as you say you are getting dry signal through the flanger it would seem that the split signal is not making it through the BBD delay path and I would recommend that you consider using an audio probe to see if and where it drops out. I assume you have tried adjusting the on-board bias trimmer as described in the instructions. Lifting one end of R25 would tell you for certain whether you have no signal through the delay.

Ok I wired in a new diode and everything except the heat sensitivity is still the same. I started reading the resistors (do this w/ power, right?) and all but a few read zero!? On R1 I get the correct reading of 470k, on R31 I get the correct 100.7k, on R35 I get the correct 100.6k, on R47 I get an incorrect reading of 125.6k, and R50 is correct at 4.7k.

Ummm...is this a short?

To repeat - most of the time you cannot expect to get accurate reading of the value of a resistor when it is connected in a circuit AND you should not attempt to even try to measure a resistor in circuit with power applied.

As I said before, the only thing you can usefully do to a powered up circuit with a multimeter is to measure voltages at specific places to see if the voltages correspond to expectations.

I hear you Tark, but I have no idea what voltages to check and where. Do you have a recommendation on where to start? I don't have an audio probe. Any ideas, Morgan?

The schematic, pcb map, and voltages are in the thread I posted above. Here they are again for reference:






And here is a voltage tutorial if you need that too: http://www.ladyada.net/learn/multimeter/voltage.html

By the way, both the flanger and ping pong delay are very noisy circuits, and neither last very long on a battery. You may find that you need to wrap each pcb in shielding material (maybe wrap each pcb in an insulator material like electrical tape, then wrap again with tin foil or shielding tape) to separate each circuit from each other as well as from outside interference. But that's not what causing the oscillation. I also worry about the length of all that wiring.

We also need better build pics. If you can get an up close shot of the front and back of the pcb, that would be helpful. Something around 900 pixels wide is good for forum viewing.

Ok, thanks I'll go through and check everything, note the values and report back. I do plan to cut the length when I figure out the mounting scheme. I will paint the interior w/ conductive paint and shield the boards as well.
I'll try to get better pics but my camera is kinda old.

I understand that you do not want to build two separate, discrete pedals. But please just trust me, that you will save yourself an extraordinaryamount of time and frustration if you get both the pedals working "stock" and separate first before attempting to do what you are attempting to do.

And please make sure that you test them each with a "normal" guitar pickup before relying on the transducer pickups too, just to eliminate that part of the equation.

Thanks for all the help everyone!
I've done the measurements and have a few odd readings:

IC2: pin7 and 8-I get 2.38 instead of 4.2 for each.
IC6: pin1 is.62-4.42 instead of 0.4-0.6 (the worst discrepancy)
IC7: pin5 is 5.04 STEADY (no oscillation) instead of 4.5-4.7 pin6 is.002 steady, not 0.2-0.5 pin7 is 3.81 steady, not 3.5-3.7
IC4: Pins 5/6/7 where says not connected I get: 5=1.06 6=.69 7=7.76 (not sure what these are supposed to read if anything)
Q2: collector=4.71 (this value drops slowly-doesn't oscillate) not 1.7-2.3
base=good
emitter=3.79 not 0......(I may have collector and emitter switched on this one)

I tried a standard humbucker and it's the same noise.
I have been testing them separately (the delay checked out ok 1st time).
Sorry I got sidetracked but wasn't sure if I should be measuring resistance at all. Does this narrow things down? Have I made a total newbie mistake?!

Q2 collector is on the south side, base in the middle, emitter to the north. The emitter is tied to ground and should have zero volts on it. Do a continuity test from the emitter to the middle lug of the input jack, and re-measure the voltage.

Here's a continuity tutorial if you need it: http://www.ladyada.net/learn/multimeter/continuity.html

I rechecked everything on Q2. No continuity between ground (jack) and emitter and i think I see why; when installing C32, the neg. lead popped off! I thought it was long enough so I installed it and marked it in red to keep it in mind. Looks like the emitter runs through neg C32 to a few more connections then to ground? I'll pick up a new C32 tomorrow and report back! I think the trace is a tad burned but is continuous w/ emitter up til the solder joint for C32.

Thanks a loooot!!! I feel like I'm closing in on it!

OK time for an update. I installed a new C32 and the constant noise from before is more random and I still don't have continuity between Q2 and ground. I think I need to fix a trace on C32 neg pole. Gonna look in that tutorial. Should I remeasure some or all of the voltages? As I jumper C32 neg to different points I am getting proper, though pretty extreme sounding flange effect so it's looking up.

I wouldn't bother until you have ground at the Q2 emitter.

OK! I repaired the trace @ C32 and now I have continuity from Q2 to ground and I have flanging!! It seems nice and quiet so I'm happy except that when bypassed, it lets a bit of signal (clock noise, mostly) through. I'm gonna go back over the components that had bad readings...will post after.

OK, the signal coming thru while bypassed (at fairly high vol) comes in with high rate and/or depth settings.
The remaining bad readings (the trace repair fixed many) are:

IC3: pins7/8 are oscillating subtly @ 3.8-3.9 instead of steady 3.5
IC2: pins 7/8 slight oscillation 3.09-3.17 instead of 4.2 steady
IC4: pins 5/6/7 are @ .85/.57/7.68 instead of "not connected" (not sure if these should read 0)
IC6: seems like the worst- pin1 is oscillating .62-4.42 instead of .4-.6
Q3: collector osc. .25-.52 instead of osc. .6-1.0

Thanks for the help everyone. Didn't have much hope for getting it done this year before posting!