Help on a very common problem

[Luqqas]

Hi there, this is simple but don't want to be repetitive: I've made more than 10 projects. but recently finished the Blue Magic and I've a loud pop when it turns on, and all is perfect when its turned off, no pop when the effect goes off. The problem is when the effect goes on. I've put a pull-down resistor at input and also, have read the DC and the measure gives 0.09 and 0.4 mV, which is acceptable (by the way, think that I could be doing the DC measurement wrong). I'm using 3PDT with no LED indicator.

Any ideas?
Thanks. Best for all!

[Govmnt_Lacky]

Double check your pull down resistor at signal input. May have mistaken the wrong value.

[Luqqas]

Govmnt_Lacky: Ok. I've done that, but still pops. First, I used 2M2, according to the GGG layout, and then try with 4M7 and the same. Also, double check traces and wiring. And to make this more complex, I've plug in into 2 different amplifiers and the same.

I'm really confused about that pop.

[Mike Burgundy]

Might be the switch - some just pop through contact and/or bounce problems.
If there's resitors to ground on in- and output of the circuit, DC-blocking caps that aren't leaky and the external circuitry doesn't put DC on your pedal (had that happen, debugged a pedal for two days before I found out it was the BOSS before it charging up the pedals input with DC) it's almost definitely the switch.
BTW, if a 2M2 doesn't do it, you'll want to try lower values. 1M is just fine. This resistor bleeds away any DC to ground, lower values bleed away more (less DC, less pop - also less signal into the circuit and less input impedance) while higher values bleed less (everything the other way round)
Oh, one more possibility - just to make sure it's not adding to the problem disconnect the indicator LED (if any) and see if it still pops. It's quite possible for a LED to pull enough current to create a pop right through the power supply.
hih

[Luqqas]

Might be the switch - some just pop through contact and/or bounce problems.
If there's resitors to ground on in- and output of the circuit, DC-blocking caps that aren't leaky and the external circuitry doesn't put DC on your pedal (had that happen, debugged a pedal for two days before I found out it was the BOSS before it charging up the pedals input with DC) it's almost definitely the switch.
BTW, if a 2M2 doesn't do it, you'll want to try lower values. 1M is just fine. This resistor bleeds away any DC to ground, lower values bleed away more (less DC, less pop - also less signal into the circuit and less input impedance) while higher values bleed less (everything the other way round)
Oh, one more possibility - just to make sure it's not adding to the problem disconnect the indicator LED (if any) and see if it still pops. It's quite possible for a LED to pull enough current to create a pop right through the power supply.
hih

Mike, thanks. I'll go a try your advices. I'll be back and post what I get.

[Luqqas]

Might be the switch - some just pop through contact and/or bounce problems.
If there's resitors to ground on in- and output of the circuit, DC-blocking caps that aren't leaky and the external circuitry doesn't put DC on your pedal (had that happen, debugged a pedal for two days before I found out it was the BOSS before it charging up the pedals input with DC) it's almost definitely the switch.
BTW, if a 2M2 doesn't do it, you'll want to try lower values. 1M is just fine. This resistor bleeds away any DC to ground, lower values bleed away more (less DC, less pop - also less signal into the circuit and less input impedance) while higher values bleed less (everything the other way round)
Oh, one more possibility - just to make sure it's not adding to the problem disconnect the indicator LED (if any) and see if it still pops. It's quite possible for a LED to pull enough current to create a pop right through the power supply.
hih

Mike, thanks. I'll go a try your advices. I'll be back and post what I get.

Ok. I've done that (1M resistor) and the pop still there. It's funny. It happen only when the effect goes on. I put a DPDT to find that it's worst. With DPDT the pop is in both actions, going on and going off. Which means that with the 3PDT (wiring with input and output grounding) the pops shows up because there is something in the input signal (the output grounding seems to work, no pop when the effect goes off). Repeat, there is NO LED.

So, I thought, perhaps I should re-check DC from amp. Anyone could tell me, just in case, the way to measure DC from amp? Is the same that with the effect (input and ground, at 200 mV?

Thanks, and if someone help me definitely, I don't know, I'll send something by mail or something. I tired of this, but don't want to give up.

Best!

[Mike Burgundy]

Okay, this has been covered over and over and over again I'm sure, but I'm also sure it can be quite daunting to filter through all the search results, so here goes -
this is now a process of elimination. Please don't be ticked off if nobody answers, there's a LOT of info on here - have you searched already? -  there's a lot going on the forum to keep people quite busy,and I truly believe your specific problem, whatever it is, is also on here somewhere. The possibilities are *many* so this might be a bit long-winded and probably won't be complete, but that's also why I think people sometimes might give priority to other things. Anyway.

The process of fault-finding is tedious and frustrating, yes, but it's also the very best learning experience, bar none. It will give you a deeper understanding of this stuff, even about bits you never thought you could possibly know more about or mattered, trust me. Sometimes it's a real insight, sometimes it's a just good story (most of us have tried debugging "dead" circuits that had *no* IC's plugged into sockets, I'm sure). Just keep it up.

It's you're choice where to start, but you have to think about a strategy, draw the right conclusions after every test, and be as methodical as you can.
Make a list of possible culprits (if in doubt if you have all of them and/or which ones are likely or unlikely, search for similar problems here or ask) and think of ways to eliminate them from the equation, such as you did by replacing the 3PDT with a DPDT.

Tip0: these are not necessarily in order, I'm basically thinking out loud after waay too little sleep, but read on:
Tip1: Try NOT to solder the switches too much - most of them don't like to be soldered very often, which may cause pops and such nasties or even the lugs and internals to shift or come loose as the casing melts. If you have some small alligator clip leads and can get them to fit, use them, or solder connecting wires to the switch and *leave them there* - solder and desolder the other end of the connections.
Tip2 - you've already done but I'll put it in for completeness' sake. Take the LED out of the equation - if it's an older style LED it might draw *lots* of current (or the circuit is especially sensitive to PS fluctuation)
Tip3 - likely causes, or some of them  (I have seen listed this several times on the forum)
Tip4 - just as an experiment, plug the pedal into the amp. Nothing connected to the pedals input. Does it pop? Does the pop go away with the pedal's volume down (it should, that's a direct short to ground now, if it's still there there's other mistakes present!) Plug in the guitar, volume open on guitar and pedal. Pop? Now close the guitar's volume all the way. Pop? What does this tell you?

*faulty/dodgy wiring, soldering, and/or cables. Switching time. Also make sure the circuit *does* work as intended, even if it pops when switched on/off. No use debugging the switch if the circuit contains mistakes, right? It happens... Check everything, then check again. Draw a new schematic from the pedal as if you're seeing it for the first time and compare. Really. Been there as well. Bungled up a MIL2 bypass and was convinced it was ok until I retraced it.

*DC on in- or output.
On the smallest setting you have on your DMM, measure both the pedal (turned on - no guitar connected but do insert a mono jack cable (just the one end) to switch the circuit on if you have a stereo jack connector disconnecting power supply ground when it's plugged out) INPUT AND OUTPUT, switch it on/off a couple of times, re-measure, repeat but make sure you're switching an odd number of times. Measure your guitar (seen it on an active bass once. Connect a jack cable just to the guitar, make sure volume is open, mute the strings and measure. Measure the amp's input also.   Caused by leaking (or missing!) coupling caps which are there to *block* DC from stuff like switches and the outside world. All caps leak a *tiny* amount which should be fixed by a large bleeder resistor to ground on the input. Output volume pot often performs this task at the output end (so don't put a cap *after* it!) If you find a voltage, you might have found the problem. Depends on the circuits (gain!) how sensitive the system is to a certain amout of mV. Caps also tend to get worse with age, abuse (too much heat for too long with the ole' iron) or misuse (such as putting an electrolytic in the wrong way round - reverse bias).

*mechanical popping from the switch.
When the switch contacts are pulled from one terminal to the other, there is a certain amount of bouncing and bad contact going on which can result in a snap, crackle or pop. Most of these switches were never designed for small-signal use!  Can get really bad on overheated switches. I've had a number of  "Xwing" switches go bad, but also the revered Carling can be troublesome!

Sudden supply current change when switching - such as when switching a thirsty LED/resistor combo, or when the circuit somehow draws waay more current when connected. It shouldn't, by the way. This is why the pedal is always "on" and we're just switching the signal.

I'm sure there might be more. DC is the most likely. Measure carefully and make sure you work methodically, via a process of elimination, and you should get it eventually.

Tip4 - when you do a normal search on several words you get a plethora of posts containing *one* of the words you typed, but you can use logical operators to force posts that contain *all* of them (try switch AND popping AND causes for example)*EDIT* - Dang. Wrong there.Doesn't work, yields many posts with the word "and".
Searching in "quotes" does yield exactly that choice of words though.

Hope it helps, happy hunting!

*edit* - keep in mind that, although rare, there might be more than 1 problem! Replacing the switch with a new one doesn't necessarily clear the switches. Hey - why not try hooking up the switch (once again use the wires already on the switch) so it's opting between bypass (regular bypass short) and bypass (connect wires to and from circuit board together) and see if that pops. If so, it's (*probably* - see before - not the circuit) either the switch, amp or guitar, maybe cables. Change amps, repeat.  Eliminate options. That's the way to think!
If all else fails (which I doubt) , then try posting again with *all* relevant data (circuit used, wiring diagram, power hookup, build pics, measurement equipment type and settings, everything from the "what if it doesn't work" sticky and a detailed logbook (keep one!) of everything you did including the results/findings. As said, I sincerely doubt it has to come to that. On the other hand, I've abandoned circuits that I just couldn't get debugged (must've missed something simple, it usually is) and just, carefully, built another one which did work.

[KazooMan]

This might help

http://www.muzique.com/lab/led.htm

[Mark Hammer]

Here's an easy meterless test for whether audible switching pop is a matter of the pull-down resistor or the switch itself.

The reason we need the pull-down resistor is because charged stores up in the input cap (and output cap too), and has nowhere to go unless there is a pull-down resistor.  As Mike (hey, welcome back, guy!  long time no see) noted, smaller values drain the stored charge off faster.  When the charge stored in the input or output cap has had adequate opportunity to drain, either by virtue of leakage or a terminating resistor to ground, you don't hear a pop.  So, if you step on the bypass switch a few times, and switch back and forth, without adding any new signal, the pop that is so audible the first time you switch becomes inaudible after a few switches back and forth.  If that's the case, then that suggests the pull-down resistor is perhaps a bit too high a value, and you could stand to drain off the charge a little faster via a lower value.

However, if the pop happens no matter how many times you switch back and forth, then the popping is coming from a source other than your inpt or output caps not draining off sufficiently.

[Luqqas]

Okay, this has been covered over and over and over again I'm sure, but I'm also sure it can be quite daunting to filter through all the search results, so here goes -
this is now a process of elimination. Please don't be ticked off if nobody answers, there's a LOT of info on here - have you searched already? -  there's a lot going on the forum to keep people quite busy,and I truly believe your specific problem, whatever it is, is also on here somewhere. The possibilities are *many* so this might be a bit long-winded and probably won't be complete, but that's also why I think people sometimes might give priority to other things. Anyway.

The process of fault-finding is tedious and frustrating, yes, but it's also the very best learning experience, bar none. It will give you a deeper understanding of this stuff, even about bits you never thought you could possibly know more about or mattered, trust me. Sometimes it's a real insight, sometimes it's a just good story (most of us have tried debugging "dead" circuits that had *no* IC's plugged into sockets, I'm sure). Just keep it up.

It's you're choice where to start, but you have to think about a strategy, draw the right conclusions after every test, and be as methodical as you can.
Make a list of possible culprits (if in doubt if you have all of them and/or which ones are likely or unlikely, search for similar problems here or ask) and think of ways to eliminate them from the equation, such as you did by replacing the 3PDT with a DPDT.

Tip0: these are not necessarily in order, I'm basically thinking out loud after waay too little sleep, but read on:
Tip1: Try NOT to solder the switches too much - most of them don't like to be soldered very often, which may cause pops and such nasties or even the lugs and internals to shift or come loose as the casing melts. If you have some small alligator clip leads and can get them to fit, use them, or solder connecting wires to the switch and *leave them there* - solder and desolder the other end of the connections.
Tip2 - you've already done but I'll put it in for completeness' sake. Take the LED out of the equation - if it's an older style LED it might draw *lots* of current (or the circuit is especially sensitive to PS fluctuation)
Tip3 - likely causes, or some of them  (I have seen listed this several times on the forum)
Tip4 - just as an experiment, plug the pedal into the amp. Nothing connected to the pedals input. Does it pop? Does the pop go away with the pedal's volume down (it should, that's a direct short to ground now, if it's still there there's other mistakes present!) Plug in the guitar, volume open on guitar and pedal. Pop? Now close the guitar's volume all the way. Pop? What does this tell you?

*faulty/dodgy wiring, soldering, and/or cables. Switching time. Also make sure the circuit *does* work as intended, even if it pops when switched on/off. No use debugging the switch if the circuit contains mistakes, right? It happens... Check everything, then check again. Draw a new schematic from the pedal as if you're seeing it for the first time and compare. Really. Been there as well. Bungled up a MIL2 bypass and was convinced it was ok until I retraced it.

*DC on in- or output.
On the smallest setting you have on your DMM, measure both the pedal (turned on - no guitar connected but do insert a mono jack cable (just the one end) to switch the circuit on if you have a stereo jack connector disconnecting power supply ground when it's plugged out) INPUT AND OUTPUT, switch it on/off a couple of times, re-measure, repeat but make sure you're switching an odd number of times. Measure your guitar (seen it on an active bass once. Connect a jack cable just to the guitar, make sure volume is open, mute the strings and measure. Measure the amp's input also.   Caused by leaking (or missing!) coupling caps which are there to *block* DC from stuff like switches and the outside world. All caps leak a *tiny* amount which should be fixed by a large bleeder resistor to ground on the input. Output volume pot often performs this task at the output end (so don't put a cap *after* it!) If you find a voltage, you might have found the problem. Depends on the circuits (gain!) how sensitive the system is to a certain amout of mV. Caps also tend to get worse with age, abuse (too much heat for too long with the ole' iron) or misuse (such as putting an electrolytic in the wrong way round - reverse bias).

*mechanical popping from the switch.
When the switch contacts are pulled from one terminal to the other, there is a certain amount of bouncing and bad contact going on which can result in a snap, crackle or pop. Most of these switches were never designed for small-signal use!  Can get really bad on overheated switches. I've had a number of  "Xwing" switches go bad, but also the revered Carling can be troublesome!

Sudden supply current change when switching - such as when switching a thirsty LED/resistor combo, or when the circuit somehow draws waay more current when connected. It shouldn't, by the way. This is why the pedal is always "on" and we're just switching the signal.

I'm sure there might be more. DC is the most likely. Measure carefully and make sure you work methodically, via a process of elimination, and you should get it eventually.

Tip4 - when you do a normal search on several words you get a plethora of posts containing *one* of the words you typed, but you can use logical operators to force posts that contain *all* of them (try switch AND popping AND causes for example)*EDIT* - Dang. Wrong there.Doesn't work, yields many posts with the word "and".
Searching in "quotes" does yield exactly that choice of words though.

Hope it helps, happy hunting!

*edit* - keep in mind that, although rare, there might be more than 1 problem! Replacing the switch with a new one doesn't necessarily clear the switches. Hey - why not try hooking up the switch (once again use the wires already on the switch) so it's opting between bypass (regular bypass short) and bypass (connect wires to and from circuit board together) and see if that pops. If so, it's (*probably* - see before - not the circuit) either the switch, amp or guitar, maybe cables. Change amps, repeat.  Eliminate options. That's the way to think!
If all else fails (which I doubt) , then try posting again with *all* relevant data (circuit used, wiring diagram, power hookup, build pics, measurement equipment type and settings, everything from the "what if it doesn't work" sticky and a detailed logbook (keep one!) of everything you did including the results/findings. As said, I sincerely doubt it has to come to that. On the other hand, I've abandoned circuits that I just couldn't get debugged (must've missed something simple, it usually is) and just, carefully, built another one which did work.

Mike,
I can't describe how usable your answer was. Deep thanks.
I want you to know that I did a research in this forum, also at GEO and tech pages about this topic, have read R.G. Keen posts about this, also all those posts of guys with a strong knowledge about stompboxes. When I see that Mark Hammer made an answer here, I cannot believe it. Anyway, what I'm trying to say is that before post here, I took the job of research all the way through I was able. I read a lot in this forum and feel so proud of this sharing in the DIY community.

Now, step to the pop problem. Although I'm studying electronics, can't do a precise explanation of how I fix the pop. After try Mike's tips and make an plan and a logbook of procedures, and organize the debbuging as Mike say, the situation is that I went for a Booster and built the MXR MicroAmp and I get the pop. Then, built the Sparkle Boost and get the pop. Finally, try the LPB2 at GGG and no pop. Works very well even with a LED indicator. So, a fast conclusion is that somehow, with a NPN as a "core" of the booster I don't get the pop. But with a OpAmp or a JFET as a "core" of the booster, the pop shows up. Curious, don't? Must say that I follow especifically Mike's tips and Mark Hammer notes about pull-down resistors and do a responsable organize, checking components, measuring caps, neat wiring, carefull job.

So, OK, fix my problem. But, I'll do a meticulous work to find why with the pop shows up in the others boosters and the Blue Magic, of course.

That's all. Again, thanks.

[Luqqas]

Here's an easy meterless test for whether audible switching pop is a matter of the pull-down resistor or the switch itself.

The reason we need the pull-down resistor is because charged stores up in the input cap (and output cap too), and has nowhere to go unless there is a pull-down resistor.  As Mike (hey, welcome back, guy!  long time no see) noted, smaller values drain the stored charge off faster.  When the charge stored in the input or output cap has had adequate opportunity to drain, either by virtue of leakage or a terminating resistor to ground, you don't hear a pop.  So, if you step on the bypass switch a few times, and switch back and forth, without adding any new signal, the pop that is so audible the first time you switch becomes inaudible after a few switches back and forth.  If that's the case, then that suggests the pull-down resistor is perhaps a bit too high a value, and you could stand to drain off the charge a little faster via a lower value.

However, if the pop happens no matter how many times you switch back and forth, then the popping is coming from a source other than your inpt or output caps not draining off sufficiently.

As I said in the previous post, Mark Hammer was here. Can't believe. Deept thanks, Mark.

[zombiwoof]

If you haven't already, try the true-bypass wiring scheme that grounds the board input in bypass.  It's available many places, GGG is one.  Look for the wiring options, and pick the one that fits your pedal (with LED, no LED, etc.).  This will often help with popping issues, it's not a sure thing but I use this wiring as a matter of course.  You may or may not still need the pulldown resistors.

Al

[stringsthings]

.... So, a fast conclusion is .....

one of your problems is making fast conclusions

[Luqqas]

Maybe. but that was like a preliminar note. I know that the explanation it's not the difference between transistor's/IC's types. Otherwise we'll be attached to NPN...