Building the tap tempo tremolo

[Unlikekurt]

Thanks taylor.

I actually recently purchased and installed a new pcb due to all the bizzaro issues i was having with my original one.  I've emailed Tom as well.
At this point, my main issues are the ticking.  Which i will deal with i'm sure.  (on that topic - i'm wondering how much the current draw of the LED selected for the tempo indication impacts the ticking? - I know a blue is recommended, why?)
And lastly, perhaps the momentary switches i've tried just aren't that useful?  I mean, I can't see tapping less than 4 taps in general.  It is rather difficult to only tap twice when setting a tempo in quarter notes!!

[Taylor]

Check the last page for some talk about the LED and current, but I can't say precisely how much of a difference the selection of LED makes here. Sorry, I didn't really understand what you mean about your switches not being useful. Are you having an issue with the switches themselves, or do you mean you wish the TAPLFO would average over the last four taps for example? I can see how that behavior could possibly be more usable. That would require a code revision, which I don't know if Tom or anybody else has plans for right now. I'm no good with assembly code for now (hope to find time to work on it at some point) but perhaps someone on this forum will give it a try?

[dawnofzion]

I just finished my build but have ran into some issues.  When I plugged in the power supply the 10r resistor (next to the diode) greeted me with a nice puff of smoke and appears to be slightly roasted on the outside?!  Also, I noticed the tempo LED did Not come on.  The bypass LED functioned properly. Any ideas?

[Taylor]

The 10r resistor feeds power to the whole circuit so if it burnt out then nothing on the board will be getting power, so that explains why the LED is not flashing and presumably you have no signal through the circuit. Are you using a 1/4 watt resistor there? Some other things I can think of would be if you had installed the 5v regulator or one of the chips backwards, possibly something there would try to pull a lot of current and let the smoke out of the 10r resistor. It can be tough to solve these mysteries from afar but I suspect the 10r will keep burning up if you just replace it; there's probably a part in wrong that's making the circuit try to draw a lot of current, or a short to some pin carrying power.

[dawnofzion]

Am I correct in having the dot on the opto on the bottom right side (negative)?

Also here is a picture of the board.  You can see the roasted 10r resistor.  Anything look off?  Any ideas?

[Taylor]

Yes, if it's an NSL-32 the dot is negative. I don't see anything off there. Perhaps if the trimpots in the center of the board are all the way to one side then the opto and/or LED pulled too much current. Try setting them to the center until you get it working, then you can tweak them. You can actually replace the 10r resistor with a jumper wire to at least get power to the circuit so you can take some measurements with a multimeter. This will help you focus on where the issue lies. The 10r is there to filter power (in conjunction with the caps to the right of it) and decouple the power the supply from the circuit, but it will function if the resistor is replaced with a link. Then you can measure voltages on the ICs and transistor and regulator.

[dawnofzion]

The I had the nls-32 backwards during the first fire up so I think I roasted it also.  I have it installed correct now.

I put a jumper in place of the 10r and get nothing but a tick. The bypass signal comes through but that's it. No LEDs light up.

I used this diagram to wire up the switch.  I did this to have a tempo led (directly off the board) and a bypass led.  Was this wrong?

[Taylor]

If you've got a tick coming out of the output it may be working and you just need to tweak the trimpots, experiment with the controls and make sure the width knob is centered while testing. Check the top of this page, below the DIYSB banner as well as the main "building your own stompbox forum for sticky links for debugging. Build an audio probe and check through the circuit, and measure voltages with your multimeter.

That bypass wiring should work just fine, no conflicts.

[tuffrabit]

Hey everybody.  First stompbox build for me ever.  I made a real noob move and didn't pay attention to the wattage values for the resistors when I was searching on mouser... ended up with GIGANTICLY sized components.  They are the correct resistance values, but they're just huge.  Having some issues, hopefully it's an easy fix.  The unit is humming both in bypass and active.  I can hear my guitar when bypassed, but it hums bad.  I can barely hear the guitar when active, but the hum is worse and the guitar sounds super faint and distorted.  Also, the LED wired directly to the PCB never flashes, just nothing from it.  I followed this wiring diagram for the switch: http://imgur.com/fi592fn

Here's images of my build in it's current state:

http://i.imgur.com/CKIoSNM.jpg

http://i.imgur.com/O9DqDWx.jpg

[Taylor]

It doesn't look like the 9v and ground pads on the pcb are connected to your power jack. Is that how you have it?

[tuffrabit]

No I don't have those pads wired.  The alternate wiring method I used made it seem like those pads weren't used.  So... I would need to wire from the power jack to the pads on the board and have another wire from the 9v lug on the power jack go to second LED?

Sorry for noobishness.  This is indeed my first stompbox build.  The only other electronics I've done have been pickup replacement and wiring a keyboard matrix to a teensy.

[tuffrabit]

Got it working.  Still buzzing/humming, just not as bad.  I can hear the guitar signal, both LEDs work as expected, and best of all it actually trems and all the knobs and switches function.  Is the buzzing probably a ground issue?  Like maybe it'l go away when I put it in the metal box and the 'In' jack is grounded against the box?  Also, I've seen mention of using a TRS stereo jack for 'In' and mono for 'out'.  Currently I'm using mono for both.  It looks like that's only really needed if one using both a DC jack and a battery?

[Taylor]

OK, sorry about that, that diagram is only meant to replace the bypass wiring so it doesn't have any of the other stuff shown. The PCB for any effect will always need to be connected to power and ground and all the grounds for the whole thing should connect together.

Yes, hum can often indicate some problem with grounding, like not all of the grounds are connected together, and also depending on your house wiring and e.g. if there are fluorescent lights or other things in the room throwing out a lot of electromagnetic noise, the circuit will pick it up if it's not shielded by being inside a grounded metal enclosure.

For the stereo jack, people only use them when they want to be able to use a battery - the stereo jack is wired not actually to accept a stereo signal, but used like a switch to only connect the battery when there is a 1/4" cable inserted into the pedal. This saves the battery from draining when you're not using the pedal, because most pedals have no way to actually turn the circuit off - the bypass switch only reroutes your audio signal but does not power down the circuit when in bypass. So you don't need to use the stereo jack if you don't want to use a battery.

[tuffrabit]

Gotcha that all makes sense. One last thing, I hope... should the tempo led that's wired directly to the board always be on and blinking when the circuit has power? Regardless of whether it's in bypass or not?

[Taylor]

Well, with the alternate bypass which you used, the LFO gets shunted to ground when in bypass. The point of that was that some people's builds would tick even in bypass so this stops that. But it also means that the LED doesn't light up in bypass because the signal that would usually light it up is not present. So the extra LED which is wired to the bypass switch is there to show that the effect is on even with e.g. minimum depth or narrow pulse width which makes the blinking LED hard to see. Yet another version of the bypass could be done without shunting the LFO but adding the second LED, so that the flashing LED would stay on during bypass in case you wanted to set the tempo while bypassed - this would not stop the potential for ticking in bypass though so you'd need to fuss a bit more over tweaking the trims and keeping wires short.

[tuffrabit]

Hah, I put it a box and now it doesn't make any sound.  Oh jeez.  I've double checked that everything is wired right.  I did have a noob oopsie moment and stripped the pad off one side of the board whilst trying to remove a pot lug.  These are double sided pads though, so as long as one side is still there it shouldn't matter to much right?  I've provided a picture, but I dunno how well anybody will be able to see, it's a birds nest in there.  Are there any general troubleshooting steps I can take to find the issue?

http://i.imgur.com/9bIDJmo.jpg?1

[Taylor]

Hah, I put it a box and now it doesn't make any sound.  Oh jeez.  I've double checked that everything is wired right.  I did have a noob oopsie moment and stripped the pad off one side of the board whilst trying to remove a pot lug.  These are double sided pads though, so as long as one side is still there it shouldn't matter to much right? 

Which pad is it? There are two layers of copper traces, one on each side, which are different, not copies of each other. Some pads connect only to the bottom layer of copper, others to the top, some to both. So for example the center pad for the multiply knob only connects on the top layer, you can see it goes nowhere on the bottom. But the outer two pads both connect on the bottom, not the top. If the bottom pad of the center lug came off, doesn't matter. The bottom pad of either of the outer lugs coming off would mean the connection is cut.

I've provided a picture, but I dunno how well anybody will be able to see, it's a birds nest in there.  Are there any general troubleshooting steps I can take to find the issue?

Yes, check the links at the top of this page, right below the diystompboxes banner, as well as the sticky links that are the top posts in the "building your own stompbox" forum (that's the one this thread is in). Using a multimeter start by verifying you've got e.g. power on the IC pins that need power, that all the grounded points on the board and the external parts are connected together, then build an audio probe based on the debugging links above and test through the circuit starting at the input and checking the outputs of major bits like the opamps, and see where you lose signal. You didn't say the LED stopped flashing so that means everything on the left side of the board (viewed from the front) is OK. You just need to check through the audio stage on the right around the TL072 and the optocoupler.

[tuffrabit]

It's the middle lug of the waveform pot on the bottom of the board.

Thanks, I'll check out that link and start troubleshooting.

[tuffrabit]

If it makes a difference or not, but I'm not getting any sound out of it either in active or bypassed mode.  I wonder if the switch is bad.

[tuffrabit]

I don't get it.  The bypassed signal should be working.  Using a multimeter I can verify continuity between the tips and sleeves of each jack when the switch is in bypass.  Weird.