Problem with TriVibe build

[Marcseo]

Hi, first post here and very new to this fantastic world, so don't be to tough on me 


I have been building eurorack modules for a while now, but they all seemed to work almost at first (no wiring is a blessing), or if they did not worked, it was something very obvious like some orientation problem that would burn a component.

So I decided to build my first pedal, a TriVibe kit from Fuzzdog. This is all the info I have gathered following the forum rules (please let me know if you need something else)


1. Fuzzdog TriVibe (design by RunOffGroove)

2. https://shop.pedalparts.co.uk/TriVibe/p847124_16518666.aspx   
    http://pedalparts.co.uk/docs/TriVibe.pdf

3. I built the full kit with LFO LED, so every component, PCB, jack, pot, etc came with the kit. I did not source any components myself, nor did the PCB (that sounds like magic to me at this point). I followed the instructions step by step, except for this point "Be very careful when soldering the diodes and LED. They're very sensitive to heat. You should use some kind of heat sink (crocodile clip or reverse action tweezers) on each leg as you solder them. Keep exposure to heat to a minimum (under 2 seconds)." as I don't fully understand that method (any links or even an image of how you use crocodile clips for this?)

4. No modifications nor part substitutions. I used everything that came with the kit. I have not done the switch yet, as I am willing to get the PCB fully working before getting to that point.

5. The project is Negative Ground.

6. When I plug a battery, the LFO Led blinks and changes following the rate/speed knob. When I plug my guitar, the sound comes completely clean/no effect, as if the pedal was not engaged. This happens when I am using modes 1 and 3 (switch up and switch down positions), when I am on mode 2 (switch on the middle position) I get a very sputtery sound, like a fuzz with a dying battery (super gatey, need to play veeeery hard to get any sound, and sound comes out very distorted and broken).

7. Readings:

Im getting 8.74v from the battery, also from the circuit once I attach the battery and


IC1 (LM13700):

P01: 0.66       
P02: 5.38
P03: 4.65
P04: 4.65
P05: 3.74
P06: 0
P07: 3.74
P08: 4.65
P09: 0.67
P10: 5.38
P11: 4.65
P12: 4.65
P13: 3.78
P14: 8.89
P15: 3.78
P16: 4.56


IC2 (NE5532):

P01: 4.44
P02: 4.43
P03: 2.21
P04: 0
P05: 9.01
P06: 4.82
P07: 4.55
P08: 4.55


IC3 (TL062):

P01: 4.55
P02: 4.55
P03: 4.33
P04: 0
P05: 9.08
P06: 0.73
P07: 3.98
P08: 0.14


IC4 (TL062):

P01: 6.78
P02: 6.18
P03: 6.17
P04: 5.71
P05: 8.80
P06: 5.04
P07: 4.89
P08: 4.79

D 1-4: Read between 8.7-9   (I don't know if I am measuring these ones right, I am bit clueless with a multimeter besides reading resistor values)

D5: this LED does not turn on when I plug the battery, but when I have touched it with the multimeter probes, it does turn on 

D6: Is the LFO led, which is working, I have not measured this one.



I do get continuity from my input jack to my output jack. I don't know if I need to check this on any other joints or points within the schematic.



Cheers, I am sooo looking forward into understanding what might have gone wrong and get on with moore projects

Super thanks in advance

[mth5044]

Welcome to the forum!

You get continuity from the input tip to output tip, or sleeve to sleeve?

I suspect you are presenting your voltages wrong - the pin numbering starts from pin 1 (top left) and goes counter clockwise around the chip. It looks like you started down one side, then went to the top of the other. On the 8 pin chips, pin1 and 8 are across the top of the chip ftom one another.

With that in mind, you should see variable voltage coming off of pin 7 of IC3.

You also shouldn't have voltage on pin 4 of IC4, so something is wrong there, multimeter or circuit wise.

Could you post photos of the front and back of the PCB and your wiring?

[Mark Hammer]

1) Welcome.
2) Once you get it working, it's a nice little circuit.  I built mine into an enclosure with a smooth overdrive after it, labelling it a "Box 'o Robin", because it gives me instant Robin Trower tone.

3)  You've posted steady-state DC voltages.  Thank you.  What may enhance troubleshooting is assessing AC voltages at critical points.  For instance, if a guitar is plugged in, what AC voltage are you reading at pin 1 of IC2A, at pin 4 of IC1, at pin 8 of IC1, etc.  You're essentially identifying the continuity of the audio signal.  Unexpected drops in AC voltage will flag troublespots.

[Marcseo]

Hey! Thanks for such a quick response

Your totally right, I made a mess measuring the ICs (first time doing it)


I do have continuity from sleeve to sleeve and also if I just stick one probe into one jack and the other probe into the other jack.


Doing the new readings I have noticed that some of IC4s pins do change depending on the Speed knob (at first I had it at max, so I couldn't see the variation in voltaje, but when at its lowest speed, it does fluctuate between two values)


IC1 LM13700:

p01: 0.66
p02: 5.09
p03: 4.43
p04: 4.41
p05: 0
p06: 0
p07: 0
p08: 2.13

p09: 1.41
p10: 0
p11: 8.51
p12: 0
p13: 4.28
p14: 4.34
p15: 5.22
p16: 0.68


IC2 N3522:

p01: 4.03
p02: 4.02
p03: 2.01
p04: 0

p05: 4.28
p06: 4.29
p07: 4.41
p08: 8.53


IC3 TL062:

p01: 4.28
p02: 4.28
p03: 4.08
p04: 0

p05: 0.12
p06: 3.74
p07: 0.67
p08: 8.55


IC4 TL062 (with max speed on the knob):

p01: 4.3
p02: 3.9
p03: 4.3
p04: 0

p05: 4.3
p06: 4.3
p07: 4.3
p08: 8.55


IC4 TL062 (with min speed on the knob):

p01: 0.7 / 7.4
p02: 3.9
p03: 3.8 / 5.2
p04: 0

p05: 4.3
p06: 4.3
p07: 3.7 / 5.7
p08: 8.55


Also, when I touch p07 on IC3 with the positive probe while negative probe is touching ground, D5 turns on.

Im attaching a bunch of images, let me know if you need anything specific or any zooms. The pcbs a bit dirty cause I had to unsolder both pots (soldered them the other way around d'uh)

[Mark Hammer]

It's not a panacea, but I like to brush the copper side with something to remove the flux.  I use methyl hydrate but there are other substances.  Sometimes flux can hide a solder bridge, so eliminating that source of problems via an easier visual inspection, is a simple step to do.  Troubleshooting is fundamentally a question of "No, it's not that" and eliminating the simplest, most straightforward, causes quickly.

[willienillie]

What in the world???



47,510Ω  2%?

I've never seen a 6-band resistor before!

[Marcseo]

Im absolutely loving this community


At the moment I am under lockdown because of the virus (Spain), so I can't go and buy methanol nor extra components. I do have some stuff laying around the house that could work as a "deflux", alcohol? nailpaint cleaner (I don't know the name in english)? h2o2?

I do have some extra resistors laying around, so I can try and swop those 2 6 bands (ill check their values, lets hope I have replacements at home).

Thank you very much!

[bluebunny]

And stiff brush would get rid of the flux.  And old toothbrush, perhaps, with the bristles trimmed down?

Those two resistors should be 4K7, according to the BOM.  They got the 4 and the 7 correct; not sure about the rest of the rainbow!

[duck_arse]

[willienillie]

Ah, so 4750?  Close enough probably.

[Mark Hammer]

And stiff brush would get rid of the flux.  And old toothbrush, perhaps, with the bristles trimmed down?

I will sometimes pick the chunks away with the tip of a utility knife and then use an old toothbrush to wipe away the dust.

[Marcseo]

Hi! I ve managed to get some isopropyl alcohol and have cleaned the PCB. I don't have 4k7 resistors laying around, so I cannot swop those 6 bars one, but if their values are 4750, they should be good enough I guess


Still the problem persists:


LED blinks following the rate knob

Mode 1 and Mode 3 sound just like clean guitar, as if the effect was not engaged (no funny noises, no hiss, no hum, nothing, just the exact same sound as if bypassed)

Mode 2 makes no sound

I am starting to consider giving up on this, as I am not even getting answers from the seller itself.

I have taken a picture of a cap that got a bit burned when I was soldering. Could this be the problem? Also one of the IC sockets, although the IC is fine and I can get it out of the socket and it has all its legs intact.











Once again thank you so much for your time and knowledge! I hope you are all doing fine and staying safe during these dark times

[Mark Hammer]

Do you  have a spare LM13700 or even 13600?  I see you have all chips socketed.  When you indicate that the mode where the signal ONLY passes through the 13700 has no signal at all, that suggests that something is wrong with that chip.

[Marcos - Munky]

First of all, welcome!

Now, a few things:

I followed the instructions step by step, except for this point "Be very careful when soldering the diodes and LED. They're very sensitive to heat. You should use some kind of heat sink (crocodile clip or reverse action tweezers) on each leg as you solder them. Keep exposure to heat to a minimum (under 2 seconds)." as I don't fully understand that method (any links or even an image of how you use crocodile clips for this?)

Get a crocodile clip and put it at the leg you're soldering. Let's say you have an unclipped leg, you just put a crocodile clip at the end of the leg while you heat the point where the solder goes. This way, part of the heat will go to the crocodile clip instead of going to the diode, so you have a smaller chance of damage it by heat? Imo, not necessary at all, just solder it as any other part and be quick.

D5: this LED does not turn on when I plug the battery, but when I have touched it with the multimeter probes, it does turn on 

This led is not supposed to turn on. It's there just to correctly bias the lfo (which btw seems to be working, at least part of it - more on that later).

I have taken a picture of a cap that got a bit burned when I was soldering. Could this be the problem? Also one of the IC sockets, although the IC is fine and I can get it out of the socket and it has all its legs intact.

Nope, you didn't damaged them enough to worry about.

You're getting a clean sound on modes 1 and 3. Check the schematic, the signal goes thru IC2A and then it divides into two parts. One part goes "to the top" and it's just a clean signal, which is then mixed back via R36 or R37, that's why you getting a clean sound on modes 1 and 3. This indicates three things:
1-you connected the guitar to the input and amp to the output. Sounds dumb, but it's a common thing to spend hours debbuging a "non working" circuit just to notice you've reversed the cables (or forgot to connect the battery or something stupid like that). If you've reversed the cables, the signal wouldn't go thru IC2A.
2-IC2 is working, because you're having an output signal. So now we know IC2 (gain stages), IC4 (part of the lfo) and IC3A (voltage divider) are working. That said...
3-your problem is either on IC1 (which creates the modulation) or IC3B (lfo output).

If the problem is on IC1 part of the circuit, you don't have modulation. As pointed by Mark, the only mode which the signal only goes thru IC1 is not working, so surely there's something wrong with that part of the circuit. This can be caused by a dead IC1, dead/non connected parts around IC1, IC1 getting the wrong voltage. Well, IC1 is getting voltages (I don't know if they're the correct ones, but anyway), so all resistors connected to VA or VR are working. Before checking the other parts, let's see the IC3B thing.

The lfo is generated by IC4, which is working correctly because of the blinking led and variable voltage on this IC. Nice. Then it goes to IC3B, which sends the lfo to IC1. So, IC3 pin 7 must have an variable voltage, or else the lfo is not reaching IC1. In fact, all IC3B pins should have variable voltages, you posted a fixed voltage for those pin. Check them again, with speed set to minimum and depth set to maximum. Also check the voltages on R31, both legs.

After getting those voltages again, we can check IC1 part of the circuit. Btw, do you know how to do an audio probe test?

[Marcseo]

Marcos muito obrigado for such an in depth answer!


I have resoldered the In and Out. And checked those values.

In terms of the sound, nothing has changed. Mode 1 and 3 give clean sound, mode 2 silence


R31 is moving in between -46 and 30

IC3 is not moving at all I get the same measures I got the first time I tried it out


I have seen you can build an audioprobe very easily, problem is at the moment I don't have those extra pieces lying around. Once lockdown is over I will get the stuff to build one.


Thank you so much for your response, it shred some light into my ignorance on electronics


Hope you are all doing fine during these strange times we are living

Cheers

[Marcseo]

Ill probably some spare ICs too, in order to see if that might be the problem (my life would be so easy that way haha)

[Marcos - Munky]

R31 is moving in between -46 and 30

IC3 is not moving at all I get the same measures I got the first time I tried it out

Both sides of R31 have variable voltage?

If yes, you may have a faulty depth pot. Put a jumper between lugs 2 and 3 of the pot and check voltages on IC3B again. If voltages are variating, remove the depth pot and check the resistence between the middle lug and the other ones with pot at min, mid and max.

If no, then replace R31 with a new resistor.

[heabypedals]

Did you get this working in the end? I have built one of these today using the same PCB and it works well. I didnt use a kit, i supplied my own parts and had a dodgy IC which meant it didnt work initially.

[Marcseo]

Decided to leave it to a side, was getting a bit frustrated. I have built a bunch of other pedals since then with just minor issues (some wrong polarity or quick tuff like that)... And feeling very happy about those builts.

Ill probably get back to this one in a couple months or whatever.