Build Your Own Clone Message Board

Hi all - this is my first build. I saw some other threads that were similar to my problem, but wasn't able to apply any of their solutions to my own situation.
Here is my deal: Bypass works, the LED comes on; when the switch is engaged, all that comes out is a low clicking that tracks the rate knob and an even lower hum (sounds like a ground issue). Turning the trim pot has a click at either side and somewhere in the middle will make a "woof" sound when I sweep the pot. the trim pot has a "stopping point" -- similar to the 300 degrees rotation that other threads said to expect. I have the same issue when the power supply is used.

I rechecked all my solder joints and reflowed a couple that were suspicious, but nothing stuck out at me. Here are DDM readings on the chips:

TL022
1 Ranges from about 3 to 5.8
2 4.3
3 Ranges from about 4.53 to 4.59
4 0
5 Ranges from about 3 to 6
6 Ranges from about 4.51 to 4.66
7 ranges from about 1.3 to 7.8
8 9.16


3207
1 0
2 4.4
3 2.13
4 8.36
5 8.95
6 4.3
7 4.66
8 4.66

3102
1 9.1
2 4.4
3 0
4 4.4
5 0.3
6 8.7
7 3.1
8 8.5

Op Amp
1 8.95
2 2.81
3 1.41
4 0
5 2.77
6 2.78
7 2.76
8 9.13

Looks like the 4558 op-amp and/or the circuit around it is your problem. Pins 1 and 7 should be at around 4.5V not 8.95 and 2.76V.

With the readings you have it looks like its the IC1a (pins 1,2 & 3) half of the 4558 you should concentrate on. Pin 3 should have Vref on it (usually 4.5V). Try removing IC1 and measuring pin 3 on the socket. If it stays at 1.41 then trace the circuit back to the source of 1/2v.

I have to admit the circuit schematic gets a little confusing on this point. Usually you would bias all the op-amps with a Vref of half the supply voltage coming from a fixed resistor divider. The diagram labels various points as 1/2v but there does not seem to be a source for 1/2v. There is a 1/2vb source which is provided by a 25K trimmer. I not sure why you would want to vary the bias to the input and output op-amps. The instructions say to set this trimmer for the cleanest signal which would certainly be the case if the op-amp was properly biased. 1/2V also goes to the transistor driving the BBD so I guess borrowing the bias from there to bias the op-amp as well is a bit of a short cut.

If 1/2v and 1/2vb are in fact the same then it looks like you have your trimmer set close to the ground end or the trimmer may be faulty. Tweak the trimmer and see if you can get pin 3 and 1 of IC1 to somewhere near half the supply. Then check pin 7 for half supply too. With the op-amp biased sensibly you at least have half a chance of getting audio to go through the pedal and come out the other side even if it is not chorused.

Looking again at your pics I can see that you appear to have the trimmer fully clockwise. Re-set this to about the middle of its rotation and check your audio and your voltages again.

Thanks you so much for you thorough reply. As a baseline for your expectations i am a "solder by numbers" guy who can take readings with a DMM -- i wasn't able to follow a lot of your speculation on the circuit (sorry for being a newb). So if i read you correctly here are the actionable things i can do:



Does this mean, on a 9 volt battery, i would be looking for abou 4.5 v on pin 3 and 1 of the first IC?



Here are the voltage readings at half-way:

IC 1:

1 3.3 - 5.7
2 4.28
3 4.51 - 4.57
4 0
5 3.02 - 6.07
6 4.50 - 4.56
7 1.39 - 7.6
8 9.13

IC 2:

1 0
2 4.31
3 3.0
4 8.34
5 8.93
6 4.3
7 4.64
8 4.64

IC 3:
1 8.91
2 4.3
3 0
4 4.3
5 0.34
6 8.51
7 3.0
8 8.32

Op Amp:
1 3.71
2 3.71
3 1.86
4 0
5 3.67
6 3.69
7 3.67
8 9.1



if i understood your "half supply" request above, these numbers look pretty close. The only change is that with the effect in engage, i dont get any sound -- no clicking or anything

OK well at least that's something. Yes you are following me about the trimmer and the op-amps. I'd set the trimmer so you get about 4.5V on pins 1 and 7 of the 4558. Then those two op-amps should be passing audio.

Even if the chorus part of the pedal is not working you should get some guitar signal through it. This is because the chorus effect is created by mixing a slightly delayed version of the input with the input signal. The delay between the two signals causes reinforcements and cancellations and we hear that as the chorus effect. So even without the delayed version mixed in you should hear the straight through input signal. This travels through IC1a out of pin 1, through R20 the 47K and then through IC5b (should be labelled IC1b on the diag but nevermind) and out through the output jack.

However you get no sound at all. So check your input and output jack wiring and check your footswitch for wiring and continuity (pedal disconnected, power off, meter set to continuity or low resistance range and make sure the switch switches the centre poles across to the outer contacts). There have been some bad switches - whether these were bad as shipped or just damaged by soldering over heating is hard to say.

Really the easiest thing to do after that is knock up an audio probe and use it to see if signal is coming out of IC1A pin 1. If you have a spare suitable op-amp lying around you could try popping that in as a replacement for the 4558. In extremis you could even replace the 4558 with the TL022. You would lose your low frequency sweep oscillator but at least you could see if you got audio through the pedal.

no matter where i turn the trim pot the voltage stays at about 8.52 on pins 1 and 7
sorry -- i remeasured and was able to trim it to just about 4.5v on both pins. still no audio.




i checked it and i *think* its ok -- also i get sound in bypass, would i get no sound if my jacks were miswired? just to double check how i read the instructions:

1) tip of input goes to the "IN", sleeve goes to ground and ring goes to "RING"; on the output, tip goes to "OUT" and sleeve goes to ground. right ?



How do i test that this switching is occurring? ie, what does it mean to check that the center poles are switching to the outer contacts for example?



i dont have an audio probe, unfortunately.



i dont have an IC, but i tried swapping the chips, and no sound. pins 1 and 7 measured about -3.4v

Hold on moment. I was assuming you knew how to use your multimeter. As we found out on another thread this isn't always the case. So just to check, you have the meter set for a DC volts range suitable for measuring a 9V pedal - it will either be 10V or 20V. Connect the black or negative probe to the pedal case / circuit ground and make your measurements with the red or positive probe.

Measure the wiper of the trimmer - can you get 4.5V on that ? Does it vary between 0V and +9 as you rotate the trimmer. Does the wiper of the trimmer connect to the end of R3 1M? Does that change with the trimmer? Are pins 1 and 7 of IC1 the 4558 really at 8.52. If I am not mistaken that is not what you measured the last time you measured it. Swapping the chips around and getting -3.4 doesn't make any sense unless you had the multimeter probes reversed or the range set to something other than volts.

yeah -- black to ground, DMM at 20v DC, Red probe for measurement. i made a mistake in my first measurement. i think i was measuring a different IC or i mistakenly swapped the probed without noticing it. i realized it after i looked at the numbers. i edited my post with the correct number - i was able to get it to 4.59v.



yes



yes



I dont see resistor numbers in the instructions, but if you are referring to the 1M resistor that is two eyelets to the right of the trimmer, then on the right eyelet i get 1m resistance, on the left eyelet i get only about 25 ohms




fully counter clockwise and fully clockwise it measures 1.003M, about halfway it measures 1.008M



i made the same mistake here as i did before i edited my earlier post -- i adjusted and remeasured, got it at 4.54v -- still no audio

i forgot to measure the left side with trimmer changes in my last post, i see it goes from 6k fully clockwise to about 20ohm fully counterclockwise

I just took a reading of all the resistors -- everything looked fine but 5 resistors. ive attached a picture of the PCB from the instructions with the varied readings shown. would low resistor values account for this ?

Just saw your new post - you can't always rely on resistor measurements that are made in-circuit. The values are often influenced by other components around them. So those values dont mean anything useful.
-------------------------------------

Here's is what I was typing -

Ok that's better on the voltages anyway.

I'm working from the circuit diagram from the current downloadable instructions. There is a link at the end of the instruction notes for a PDF.

http://www.buildyourownclone.com/ce2rev11schematic.pdf

My comments about the trimmer and the 1M were to see if you got a changing voltage on the wiper and if that voltage got to the 1M to bias the op-amps. We seem to have solved that part of it, now you need to leave the trimmer were the op-amps are biased so that pins 1 & 7 are at around 4.5V.

If you have visually checked the switch wiring against the instructions and checked all of the switch works then the next thing to do is to see if your guitar signal is reaching the input of the IC1a circuit.

You check the switch by measuring resistance between the centre tags and the two outer tags. You should get a very low resistance between the centre tag and one of the outside tags (and a high resistance between the centre tag and the other outside tag). Clicking the switch should make those connections flip over. The switch has three sets of contacts - centre pole and the two outside tags the centre connects to. It is wired to switch the circuit input between the input jack for active or ground for bypass. The output jack of pedal is switched between the output of the circuit or bypass from the input jack. We need to make sure all those connections are being made. Or at least the connections required when the pedal is active.

Once we know the input signal actually connects with the input of the circuit and that the op-amps are biased at 4.5V then we should expect at least some audio to make it through the pedal. I think you said that bypass works and the LED lights but that still leaves 1/3rd of the switch - the part that switches the input that could be a problem. That is labelled SW1a 4,5 and 6 on the diagram.

As I said the easiest way to proceed after that is to build an audio probe. All you need is stiff insulated rod (like the probes that come with your multimeter) connected to the input of a guitar amp
through a cap (a 0.5uf non polarised would do). Use a screened cable with a jack plug to connect to the amp, take the centre signal wire of that cable and connect that to one end of the cap. Connect the other end of the cap to the probe. Connect the ground of the cable to the ground of your pedal. You can then touch the pointy end of the probe to parts of your circuit and if there is an audio signal there you will hear it from the amp. We want to see if audio is getting through to pin 1 of IC1a and if it is does it get to pin 7.

ok -- got it to 4.51v on 1 & 7






i wasnt sure what orientation (vertical or horizontal) you meant by 'centre" and "outer" so i measured in both directions.

Pedal on

Vertically
I get 1M between 8 and 9, 0ohms 7 and 8
it "flickers"(shows way over 1M, then cycles down) between 4 and 5 and settles at 0.00; i get 0ohms between 5 and 6
it also "flickers" between 1 and 2 and settles at "-0.00" and "0.00"; i get no reading between 2 and 3


Horizontally
i get over 1M between 1&4 and 4&7 and also between 2&5 and 5&8
i get 0ohms for 3&6 and 0ohms for 6 &9


Pedal Off
Vertically
i get that flickering between 8 and 9 -- settles own to 0 ohms; 0 ohms between 7 and 8
0.1 ohms between 5 & 6; 0ohms between 4 and 5
~ -0.3 Ohms between 2 and 3; 0 ohms between 1 & 2

Horizontally
i get 0.1ohms for 3&6
i get the "flickering" down to 0 for 2&4
i get 0 ohms for everything else


the "flickering" is where it looks like the DMM is getting a reading but it just winds its way down to "0.00" (or something "-0.00") -- i am not sure what that means. I tried taking the reading with the 5 available settings and where "flickering" is noted above, i get it at each setting.

OK lets see -

From the instructions - with the 'flats' of the 3 pole, double throw switch (3PDT) tags oriented horizontally as shown. The centre row of three tags are the 'poles' numbered 2,5 & 8. The upper row 1,4 & 7 and the lower row 3,6 & 9 are the 'throws'. When the switch is operated the centre row of poles should alternate between connecting to their associated throw tags in the upper row or the lower row. Pole 2 should connect to either 1 or 3, pole 5 to 4 or 6 and pole 8 to 7 or 9.

With the pedal 'on' but disconnected from ins, outs and power you should see close to zero ohms (an 'on' connection) between 2 & 1, 5 & 4 and 8 & 7. Between 2 & 3, 5 & 6 and 8 & 9 there should be a very high reading (or off).

Multimeters often have a continuity setting. On this setting you often find that that there is an internal bleeper that sounds when you connect the probes together, indicating there is a short between the probes. This would be the setting to use to test the switch - bleep for a switch 'on' connection, no bleep for a switch off. if your meter does not have such a setting then any high resistance range will do. Digital meters often take time to settle and often the last digit on the display will hop up and down. When you try to measure resistance in circuits that have capacitors connected to them the meter may take a long time to settle because the capacitors are either slowly charging or discharging.

In this case we are really interested in proving that you see a very low resistance connection between 4 & 5 of the switch when the pedal is switched to 'on'. This shows that the input signal from the input jack at least passes through the footswitch. You could expand from there a little and look for continuity (very low resistance) between the tip of the input jack and the junction of R1 and C1.

At the other end of the circuit for the signal to get out of the pedal we need continuity between the top of R24 and the tip of the output jack.

Hi guys,

Here are some resources for you to make things a bit clearer.

Here's the schematic:


Here's a pcb map so you can find specific components on the pcb:


Here's an image detailing stomp switch pins:


Here's a tutorial to help the OP with continuity readings: http://www.ladyada.net/learn/multimeter/continuity.html

Here's a diagram that shows how to build an audio probe out of simple components: http://www.diystompboxes.com/pedals/audioprobe.jpg

Like tark mentioned, symptoms like this point to a problem in the dry signal path. There is something between the circuit input & output that is blocking the dry signal. And those voltage readings on IC1 are pointing to a bad connection or short in the first half of the op amp. In these situations, I like to advise that you remove the BBD (IC2) from the socket and just focus on getting clean signal through the pedal when the circuit is in effect mode. Once that's accomplished, plug the BBD back in and see if the chorus part of the circuit is working.

Thanks Morgan that should help.

As to the odd voltage readings on the op-amp we seem to have solved those by ensuring that the 25K bias trimmer is set to give 4.5V on the outputs of the op-amps. This is perhaps the only BYOC pedal that does not use a fixed resistor divider for the op-amp bias.

Now we need to figure out why audio is not getting through the op-amps and dry signal path.

ahh i was trying this with the cable plugged to the in .. it is different without the cable plugged in
so in this mode, i get 0.2 ohms for 2&1, 0.1 ohms for 5&4 and 0.1 ohms for 8&7


i set the DMM to "2M" and it doesn't change for 2&3 or 5&6 of these pairs (just displays ".0L" without indicating any connection)
for 8&7 I get a reading around 1M ohms



my continuity tester unfortunately has no beep.




based on my understanding of your instructions, we appear to have this. does the non-responsiveness of the other pairs present a problem ?



i have continuity between the tip and the right-eyelet on R1, no continuity b/w tip and left eyelet

I have continuity between the tip of input and the left eyelet of C1, none with right eyelet



i have continuity b/w tip of out and left eyelet of R24, but nothing from the right eyelet

thanks so much morgan -- thats the sort of picture i needed. hopefully i can stop annoying you guy soon and get my chorus working

Good we seem to be gradually eliminating things. For good connection between two points - across a closed switch for example - you can expect your DMM set to resistance range to show you some very small resistance reading and for an open switch you would see either just a flashing 1 far left of - as you have - OL - for overload.

I wanted you to just test the characteristics of the switch. It is simply 'cleaner' to do that with the pedal disconnected.

As far as I can see the switch works and the basic signal connection reaches the input of the PCB and the output of the circuit is connected from the PCB to the output jack. That just leaves everything in between. That's both halves of the 4558 chip and all the components associated with them. Apart from simply visually inspecting those components using a bright light and a magnifying glass for correct values, good joints and possible shorts there isn't much more I think you can do without some form of audio probe.

With a probe the first thing to do would be to see if an input audio signal reaches pin 1 of IC1a. That input amplifier has a gain of 5 X so the signal on pin 1 should be a good deal louder than the input signal. if you do buy or make some kind of probe be careful about connecting it to pin 1, it is easy to slip and short out pins on the IC.

ill try a thorough inspection first -- if i cant get that working ill move on to the audio probe. Ill also check to make sure no components is burnt -- I checked the unpolarized resistors last night and they looked good. When i check the other components, what are the sorts of things i am looking for? So with a polarized resistor i want to measure resistance, but what about with capacitors and diodes?

Measuring anything while it is connected into the circuit is not always going to give you helpful results. If I were you I would avoid trying to measure components with a meter while they are connected into a circuit.

Not sure what you mean by polarized and un-polarized resistors. Resistors do not have polarity. If you measure resistance of a diode out of circuit it should show a very high resistance in one direction and a few hundred ohms in the other. If you measure a capacitor out of circuit on the resistance ranges of your meter then the small values should look like open circuits. Larger caps will briefly look like shorts circuits and then their apparent resistance will rise as they charge up from the current supplied from you meter. Although you can use a meter set to resistance to check to see if a cap has developed a short this can be a bit dodgy because polarized capacitors are not supposed to be reverse biased. By that I mean that the positive terminal of the cap should always be connected to a positive voltage. Tantalum capacitors in particular do not like being reverse biased.

so apart from a careful visual inspection, the only way to find a bad component is the audio probe, right ? if i build the audio prove, is there a series of points i should try ?



sorry -- i was thinking of the large caps

Well like I said the first point to try is pin 1 of IC1a. If the audio signal is reaching the PCB and is being amplified by that op-amp you should get a really strong signal there. That would mean that the dry mix resistor R20 is getting fed for the dry part of the signal and that the input of the BBD should be getting signal. If you can establish there is a strong signal on pin 1 of IC1a then you should check pin 7 of IC5b (mislabelled - it should be IC1b). If the signal gets as far as pin 7 then there is not much to stop it getting out of the pedal - just a resistor cap and the switch. We have checked the switch and have continuity between the out jack tip and one end of C15. So in that case you would look for a signal at the junction of the 470 R23 and the cap. If you had signal on one end of that resistor but not the other you either would have a bad resistor or a bad solder joint.

However what I suspect you will find is no audio on pin 1 of IC1a. By the way for an audio source you should use something like an output from a radio or CD player so you have a constant signal, rather than having to strum a guitar. if there is no audio on pin 1 either IC1 the 4558 is faulty or there is something wrong with the circuit immediately around it.

Previously I said that input amp has a gain of 5 - not quite right - it has a treble boost of 5 and a gain of 1 at low frequencies. Don't expect a strong input signal at pin 2 because this is a low impedance point. However you should see a signal where C2 and R2 connect.

i built the probe and tested pin 1 of the first IC chip (TL022) -- all i get is a clicking sound that corresponds to the rate

by the way i also verified the probe works by attaching it directly to the ground and hot signal of the input jack -- heard the guitar in the amp.

i checked my drawer and have a bunch of other chips in a similar size available -- do you happen to know if a "TL071" would work in the place of the TL022?

As far as I recall a TL071 is a single op-amp and the two op-amp chips in your pedal are duals - so no the TL071 wont do.

You say the first chip and then you say TL022. Does that mean you swapped around the 4558 and the TL022 as per one of my previous posts and then left it that way?

If by first IC you mean the TL022 and that chip is in the socket BYOC intended it to be then you probably would hear only a clicking sound. That is part of the LFO circuit.

Lets get the 4558 back where it is supposed to be (if it isn't) then check pin 1 of IC1a (or the junction of R5 and R20 - same thing) as indicated by the circuit diagram. If you have no signal there then the fault you are chasing can only be in a very limited area of the circuit.