Building the tap tempo tremolo

[Noodlerks]

Hey Everyone,

Just finished putting this thing together. The LFO & LED seem to be working and the Depth,Tempo, Waveform, And Multiplier pots seems to work as well. I'm not getting any sound. I've searched through about 22 of the 48 pages on this thread and tried setting all 3 internal trims to the middle including the  wave distort pot. Still nothing. I've attached a link below with a photo of the PCB.

Please note that I have not done the off board wiring as I use a little test box to hook everything up to limit possibilities during troubleshooting.
I also wiring the NSL-32 on the backside of the pcb. Long leads on the resistor side. The white dot is on the trim pot side on the pad that isn't marked with "+"

Thanks in advance!

https://postimg.org/image/t9h06apjl/

[Taylor]

With an audio probe, check if you have audio at pin 1 of the TL072 (first opamp output), and if so, then check pin 7 (second opamp output). That'll narrow down the issue to before or after (including) the optocoupler.

Also, make sure you've got the wave distort knob centered while testing. It's possible to get silence with certain settings otherwise, which would make debugging more annoying.

[Noodlerks]

Thanks for the quick response. I'm getting signal from Input to Pin1 of the TL072. I am also getting signal from Pin7 of the TL072 to the output. I'm guessing it's something to do with the NSL-32. Wave Distort is set to center position. Solder connects look fine but I'll do some reflowing if anything looks shady. I'll order a new one and let you know.

[Noodlerks]

That indeed was the problem. This thing is excellent. Thankyou!

[Taylor]

Glad you got it sorted - happy tremming!

[Mgt280y]

I know this is a straight forward problem but can't won't out the best way to fix the build doc page 7 shows how to wire the 3pdt to include the visible led (tap tempo) but no on/off led for bypass/effect I thought I could go from dc plug +ve to clr to led to ground but there isn't a ground Conection on the 3pdt that is made when the effect is on? Or have I missed something

[slacker]

The way the switch is drawn on page 7 of the docs the visible tap tempo led is turned off when the effect is bypassed and flashes when the effect is on, so you don't need a separate bypass/effect led.
If you wanted to you could wire the tap tempo led straight to LED pos and neg on the board and it would flash all the time, you could then add a separate bypass/effect led to the 3pdt. This means you can see the tempo when the effect is bypassed if that's useful.

[Mgt280y]

That would work I wanted the bypass led for the artwork design as much as anything. So does that mean the tap led will flash all the time when dc is plugged so could be used as a tap tempo without any effect being on (essentially a led silent metronome) as that might be useful anyway

[slacker]

Yeah, the tap led will flash if power is on.

[Mgt280y]

Right fired this up for the first time, no audio so far checked pin 1 TL072 and I got it there but nothing on pin 7 does that mean it's the Opto ?

[Taylor]

Probably so, if your flashing LED is flashing. If the LED is also not flashing, then the digital side is not working yet.

[Mgt280y]

No flashing led either, the only time it has flashed is if I touch I think pin 3? I think On taplfo with my DMM
If I touch it comes on hold it against it flashes?

[Taylor]

OK, maybe the next step would be to measure the voltage at each pin of the TAPLFO chip and also the 78L05 and post them here. It's usually easier to get the LFO working first, then the audio section.

[Mgt280y]

I'll measure all the pins in the morning, does it matter what position the pots are in?

[Taylor]

Not for measuring voltages, but I'd just set them all in the middle while debugging.

[Mgt280y]

1- 4.93
2- 2.03 *
3- 2.34
4- 4.93
5- 0 (4.91*)
6- 0
7- 0
8- 4.93
9- 1.88
10- 0
11- 0.68
12- o
13- 0 (1.52*)
14- 0

1- 4.49
2- 4.49
3- 4.46
4- 0
5- 0 (4.49*)
6- 0 (4.49*)
7- 0 (4.49*)
8- 8.99

2 when I touch this with the dmm it makes the led flash if led is off voltages non brackets if touch pin and led is on voltages in brackets

[slacker]

Pin 2 of the taplfo chip is one of the pins that goes to the crystal, if there's a problem round there the chip won't run which is why the LED isn't flashing. If touching it with your DMM makes it work then you might have a dodgy connection to the crystal, I would check and reflow the solder joints to pins 2 and 3 and the crystal and the two 22pF caps. If that doesn't solve the problem then make sure you haven't got any solder blobs shorting out those pins and clean off any flux, if it still doesn't work you could try making one or both of the 22pF caps a bit bigger, sometimes the crystal might need bigger caps.

[thpmink]

I'm planning to implement the switchable expression pedal input for depth and speed as shown in this scribble by Taylor:


1.) Where would be a good point to take the +5V for the TRS jack? 

2.) "TS" in the picture refers to "Tip-Switch", right?

Thanks!

For the record, I have some ticking on this build too...  Raising the 330p Cap to 1n didn't do much. After careful adjustment, I can get it to a point where it only occurs on the ramp up and square wave, and only when there is signal (i.e. when you turn your guitar volume knob all the way down it doesn't tick), but it's still noticeable to a degree where it's annoying. Could replacing C13 with a giant 470uf cap help? Higher gain transistor for the LED in the vactrol? I'll probably have to try different vactrols too I guess...

[Taylor]

1. The leftmost pad for the Tempo pot is connected to 5v, so that might be an easy spot to solder to.

2. That's right - I think when I drew that it was referencing a particular jack somebody was going to use, so the drawing made more sense when looking at the photo for the jack.

C13 is bypassing the reference voltage for the opamps. It might be more useful to add another larger bypass cap between 5v and ground (leave C15 in place and add a larger one in parallel), since the LED and opto are pulling from the 5v rail, and the ticking is more likely IMHO coming from that sudden onrush of current on the vertical segments of the square and ramp waves.

[Andrew B. Campbell]

I'm revisiting this after some time to update with my build. I'm having the same issue that someone had earlier with the fact that nearly every feature works except for the fact that no audio is present when the effect is engaged. The LFO indicator monitors modulation speed accurately, all of the knobs (even the rotary for waveform) work perfectly.

When bypassed, there is no ticking and my guitar plays through smoothly. As soon as the effect is engaged, the audio is lost except for some low-volume ticking when Ramp Up/Down and Square waves are chosen. I will also say that IC - 2N3904 is the only component that becomes rather hot to the touch, even after switching out between others. I've recently placed sockets where the 330pf capacitor would be to see if changing out the capacitor between different values would aid in some way. I've also switched between three different TL072 Op-amps.

It should also be noted that the trimpots don't do much of anything in the way of decreasing the ticking or affecting the LFO indicator's brightness in the slightest. Also, with the alternative wiring method, the LFO indicator does not activate. Only when I have both NEG and POS leads attached to the board does it function properly. I have no idea where to go from here.

Any help would be appreciated!