Building the tap tempo tremolo

[ElectricDruid]

Sounds like there's something seriously wrong around the 2N3904. That shouldn't be getting hot.

If that's true, and there's a mistake there somewhere, that'll explain why there's no audio. Without that transistor turning the optocoupler on, you'll be stuck at permanently off.

HTH,
Tom

[Andrew B. Campbell]

It's just strange that every feature is working properly outside of the audio. I'll check to see if I have an incorrect resistor or cap values somewhere perhaps. If that doesn't work, I'll order in a new NSL-32. If THAT doesn't seem to alleviate the issue, I'll just resort to seppuku.

[Taylor]

Since you're saying all the knobs work but the audio path doesn't, the LED must be flashing, but you also said that the LED indicator doesn't activate. I'm sure that I just misunderstood part of that, but could you clarify what the LED is doing?

If you hear ticking but no guitar, that tells us that everything in the audio path after the optocoupler to the output is probably working. It could be a short/open somewhere between the input pad on the PCB and the opto.

But as Tom says, the 3904 heating up, and what you said about the trims seems to point to an issue with that transistor. You've probably already checked over all this, but make sure it's the right part number (and not, say, a 2n3906) and it's in the right way. Can you post voltages for all the pins of the transistor and ICs (including 78L05 regulator)?

[Andrew B. Campbell]

I found the issue was a destroyed pad where the 100uf electrolytic was alongside the transistor. I was able to get it to work for just a brief moment and endowed the trimpots with the ability to adjust the LFO indicator, but it died shortly afterward and then the 10 Ohm resistor burnt to a crisp. I started this build when I was relatively new to being a DIY pedal enthusiast, so I'm going to purchase another PCB and try this again. With the new 3PDT boards I purchase for another build, everything should be pretty simple to adjust now that I have a bit more experience.

Thanks again guys.

Let me know if you happen to have some more boards shipped in so that I may order from the site.

[Taylor]

The board might still be salvageable - if you post a photo I could give a suggestion on an alternate way to connect the parts with lifted pads. Sometimes it's easy to swing a component leg over to a via that the pad was connected to. But, the tap tempo trem boards are in stock if you wanted to start with a fresh one.

[dafortier]

Here's one I haven't seen yet. Just built this one and like everyone else, I have some ticking. Been able to trim it out mostly. And it's only on the first three wave forms, however, it's there even when the effect is off. Most pronounced when it's off actually.

I'm not sure why it's passing through even when it's bypassed. My 3PDT switch is wired per the drawing build doc.

I suspect a grounding issue but not sure where it could be.  The board ground is wired to the neg on the power jack and then to the sleeve of the input jack.

Any ideas?

Sent from my VS995 using Tapatalk

[Taylor]

Here's the alternate version of the bypass wiring, which grounds the LFO signal while bypassed, should solve the ticking in bypass:

http://imgur.com/fi592fn

[dafortier]

Here's the alternate version of the bypass wiring, which grounds the LFO signal while bypassed, should solve the ticking in bypass:

http://imgur.com/fi592fn

Yep. That worked like a champ. Thanks!!

Sent from my VS995 using Tapatalk

[dafortier]

One more thing. I many have fried something.

I re-boxed it and while doing so, I made a couple of changes.

I socketed c15 so I could try different values. I inserted a 1uf to try first.

Also removed the wave distort knob and soldered in the resistors in its place.

I wired the led directly to the PCB, bypassing the switch so it's always on.

Lastly I added a status led.

When I first powered it on it worked for about 15 seconds then it just shut off. Took it back to my work bench and plugged it in and the resistor right next to the rectifier diode got red hot and burned out!

I replaced c15 with it's proper value and replaced the diode and resistor. Same thing happened.

Someone know what's causing that resistor to overheat? Where should I start looking? I already checked for shorts or solder bridges.

Sent from my VS995 using Tapatalk

[dafortier]

One more thing. I many have fried something.

I re-boxed it and while doing so, I made a couple of changes.

I socketed c15 so I could try different values. I inserted a 1uf to try first.

Also removed the wave distort knob and soldered in the resistors in its place.

I wired the led directly to the PCB, bypassing the switch so it's always on.

Lastly I added a status led.

When I first powered it on it worked for about 15 seconds then it just shut off. Took it back to my work bench and plugged it in and the resistor right next to the rectifier diode got red hot and burned out!

I replaced c15 with it's proper value and replaced the diode and resistor. Same thing happened.

Someone know what's causing that resistor to overheat? Where should I start looking? I already checked for shorts or solder bridges.

Sent from my VS995 using Tapatalk

Nvmd.. I'm a dummy. Don't hook up a 12v power supply to a 9v circuit.

Can delete this and the previous post.

Sent from my VS995 using Tapatalk

[Taylor]

Edit: ah, glad it worked out. 

Original post:
If your status LED is taking power from the board, maybe try wiring it straight to the power jack instead. You could also try replacing the resistor that burnt out with one double the value - it has to do with filtering the power so changing this value won't affect the audio or LFO function.

[ferdinandstrat]

Hey guys, did anyone encounter a problem where occasionally the pedal will lose volume when bypassed?

[Taylor]

If you've wired it up as true bypass using a regular 3PDT switch, then you might have an intermittent wire/cold solder joint on your bypass switch or somewhere in the ground wiring off-board.

[cnspedalbuilder]

Hello, I am almost done w/this project (fingers crossed) and am thinking of boxing it w/board-mounted pots. I was wondering if anyone has a drill template designed for board mounted pots?

[telebiker]

Hello!

Just curious, has anyone succeeded to swap taplfo2 to taplfo3 in this pedal? Not sure how it is possible. I would appreciate if anyone could share ideas

Information regarding updated chip can be found here: https://electricdruid.net/product/taplfo3/

[ElectricDruid]

Oo oo oo! I know this one! I know this one!!

The TAPLFO3 can be used in the MusicPCB board without serious changes. One thing we aimed for when we did the new chip was to keep it compatible as far as possible. The differences are all listed on page 6 of the datasheet:

https://electricdruid.net/datasheets/TAPLFO3Datasheet.pdf

For the MusicPCB Tap Tempo Tremolo project the differences should boil down to:

1) Don't solder in the crystal or the two 22pF caps next to it. The new chip doesn't require a crystal.
2) Don't solder in the 10K on the tap tempo switch input (next to the 22pF caps you just ignored)
3) Don't solder in the 10K on the EXP switch input (furthest left of the three below where it says WAVE D|STORT). This is for the "Next Multiplier" switch, but this feature doesn't appear on the new chip.

That should get the PCB working with the new chip.

In addition, there are two new features:

1) If you add a SPST toggle switch between the two pads for the 22pF cap connected to pin 3 (e.g. pin3 connected to ground), you can select a new set of waveforms.
Incidentally, don't ground Pin 2 - it makes the pots work backwards! (This is actually helpful if you're using op-amp mixers to supply control voltages to the chip).

2) If you have problems with ticking, you can ground pin6. This activates the waveform smoothing filter giving all waveforms a 20msec rise/fall time. This should help reduce ticking noises.

I'd be interested to know how people get on with this - I haven't yet tried it myself, although I have a PCB around, so I could if I got my a$$ in gear.

HTH,
Tom

[alparent]

Just about to finish this  one. I have a TAPLFO2d in it right now.
I can try the TAPLFO3c ....... I have a PIC 16F1824 I can burn the code on.
What would be the biggest advantage of going 3c over 2d (other then having more wave forms?)

I also have a midwayfair tap tempo Cardinal I need to finish. I'll keep the TAPLFO2d for that one.......maybe!

[ElectricDruid]

Just about to finish this  one. I have a TAPLFO2d in it right now.
I can try the TAPLFO3c ....... I have a PIC 16F1824 I can burn the code on.
What would be the biggest advantage of going 3c over 2d (other then having more wave forms?)

I also have a midwayfair tap tempo Cardinal I need to finish. I'll keep the TAPLFO2d for that one.......maybe!

Aside from "more waveforms", the biggest plusses for me are "less ticking" and "no crystal". The filtering should make getting a nice quiet tremolo much easier, even with the difficult waveforms like the ramps and the square. And the crystal is a part most people don't have lying about and it uses up two pins, so it had to go!
The frequency range, wave distortion, and multipliers and stuff is all unchanged, at least from a user's point of view. The waveform resolution and sample rate were improved too, but you probably won't hear that on a tremolo.

[alparent]

What I'm I suppose to do with all those PIC 16F684 now!?

[ElectricDruid]

What I'm I suppose to do with all those PIC 16F684 now!?

??