Help me troubleshoot my first build please!

[Boiller]

Hi everyone, nice community you guys have here and today I'm joining you in hopes to receive some guidance.

A short background on me, I'm a 28 year old Comp. Sci. MSc who always had a disposition for tinkering. When I was a kid (some 15 years ago) I was fascinated with DIY electronics, small circuits and such when I joined some computer overclocking and watercooling online communities. Fast-forward, I play guitar for a couple of years now, started buying pedals and discovered the wonderful world of DIY stomp boxes! So for my birthday last week, I gifted myself a couple of DIY kits and some supplies. Now I just finished assembling my first kit, a Musikding FOXX tone machine fuzz kit, but as I expected, it does not work.

Also, this project was my soldering school and I am now pretty confident that I can do some decent connections, but the first few leads were quite troublesome, aggravated by the fact that I tried using some older soldering wire I had laying around (for 15+ years), which either oxidized or wasn't 60/40 as I believed, making a mess of my first solder (1 leg on R1).

So, on to the build description:

First of all, here is a small imgur album with the provided Musikding schematic, wiring scheme and some photos I snapped of my project. If you need more/better photos or a description of each, please do ask.

The kit is the Musikding FOXX fuzz, an octave up fuzz. I did no modifications other than not including the battery clip.

Issue: pedal bypasses guitar signal, with the pedal on or off (always). When turned on, LED does not light up (although + lead reads 9v).
Problems I already identified:

• I believe diodes D3 and D4 are not working. In diode test mode, the multimeter is reading values in both directions. This is probably due to the first installation where I had reversed the polarity, and as being a newbie at soldering/desoldering, I might have applied too much heat. While the diodes tested alright when this happened, I now tested again and seemed to go bad.


• Side note question on this: if a diode such as this goes bad, does it mean the pedal will be mute when turned on, or just fizzle crackle and whatnot?


• R1 might be cold jointed, as this was my first solder as I mentioned before, no voltage read comes through this resistor.

So now I'm asking you guys for your expertise, namely I'd appreciate if you'd glance over the picture album and identify any obvious mistake I've made. On the 3PDT switch, does the diagonal connection include the middle lug? Also, if the LED + reads 9v, should it not light up? Where can I find information on what voltage ranges I should be reading on certain components?

By now I'm a bit demoralized, but I do have a tremolo kit next in line so I'd like to get my troubleshooting skill up to par with this project first and get atleast a semi-working pedal before I try to tackle any other new project.

Thanks for reading!

[robthequiet]

Welcome, Boiller,

Just a quick observation, is that the general concept of Ohm's law will help you find some answers as to which voltages to expect at the end of a resistor. More simply, using a meter to check for continuity is one way to check for shorts or opens. If the switch is where the issue is, you can check for continuity on the lugs to make sure that the signal path is where it should be.

Thanks for posting photos, this will help a lot.

[Plexi]

Welcome!
For be the first time, you made a really GOOD job!
Very clean... you have to see my first pedal years ago 
About the diodes, is possible if you heat them too much time.

The transistors provided are the same indicated in the schematic?

In your place, I would avoid some heat-shrink tubing (only in critical junctions), and left the jacks and overal contruction with less ground cables.
Think that the enclosure is fully grounded

[robthequiet]

Ah. OK, so the next set of information might be to measure the voltage on each leg of each transistor, carefully not to short them, of course. That will tell us if they are biased correctly.

Let's not worry about the LED for now.

There is another test device that's useful which would be an audio probe. This might be a good read.

Edit: I agree with Plexi, very nice build.

[EBK]

I really gotta laugh, because after reading your description, I was expecting to see a mess when I opened the pics.  It looks quite good, actually.  I am very happy to see sockets for your transistors, especially when you are new to soldering.

As for D3 and D4, take a closer look at the schematic to see why you are getting a measurement in both directions (as you should be). 

R1 is a pulldown resistor, designed to prevent popping when you switch the effect on.  If it is not soldered well, everything should still work fine without it.

If those diodes were bad, you'd get a louder output, probably clipping at the output stage.  It wouldn't be dead silent.

Here's my suggestion, based on what I see:


Measure your voltage going into the board to make sure the value and polarity are correct.


Print out a copy of that wiring diagram.
One wire at a time, double check that each end goes where it should.
Once you've checked a wire, use a highlighter to mark it off on your printout.

At this point, I suspect a wiring problem. 

Edit:changed the order of my suggested procedure. 

[EBK]

One other obvious thing to get out of the way.  I see you are mounting the board on standoffs and the pots are mounted slightly under the board.  Do they have enough clearance so they aren't shorting anything on the board?

[Boiller]

Thank you so much for the quick replies, and you'll laugh even more when you read this. So I thought to myself, I've never heard this footswitch click. I kept trying, until I grabbed the footswitch from the tremolo kit I have around, and lo' and behold, it clicks. Switched them, it works!

Now I have a functioning fuzz! It actually works to my amazement, albeit very noisy and my lack of experience with pedals in general can't discern if it's its character or a "faulty noisy".

Meanwhile I was waiting for your replies, I did measure transistors:

T1	T2	T3	T4
E: 0.15	E: 1.62	E: 0.23	E: 0.23
B: 0.72	B: 2.22	B: 0.82	B: 0.78
C: 2.23	C: 7.34	C: 7.02	C: 7.80

Are these in acceptable ranges? I really need to study up on these.

One other obvious thing to get out of the way.  I see you are mounting the board on standoffs and the pots are mounted slightly under the board.  Do they have enough clearance so they aren't shorting anything on the board?

This was actually another issue I'd like to ask opinions on. Since I drilled the enclosure myself a bit different from the Musikding "template" and I really didn't think about the PCB placement, it'll have to be on the stands, but not fully secured, only resting on the tips of the stands. Any deeper and it would indeed short on the pots. What would be a good solution for this? I'm thinking hotglue on the stands?

As for D3 and D4, take a closer look at the schematic to see why you are getting a measurement in both directions (as you should be). 

If those diodes were bad, you'd get a louder output, probably clipping at the output stage.  It wouldn't be dead silent.

As I mentioned, it is awfully noisy which can be drowned out by a hefty volume, but still, could it be a symptom of bad diodes then? Also, if I'm thinking correctly, the octave effect is "on" when the SPDT switch is tilted to the soldered lug correct? If so, the effect is not as pronounced as many demos I've seen in YouTube. Is there any definitive way I can check the diodes health now that they're on the circuit?

I will also consider an audio probe as a project, seems very useful to have!

Thank you all for your help

[EBK]

Thank you so much for the quick replies, and you'll laugh even more when you read this. So I thought to myself, I've never heard this footswitch click. I kept trying, until I grabbed the footswitch from the tremolo kit I have around, and lo' and behold, it clicks. Switched them, it works!

excellent!

This was actually another issue I'd like to ask opinions on. Since I drilled the enclosure myself a bit different from the Musikding "template" and I really didn't think about the PCB placement, it'll have to be on the stands, but not fully secured, only resting on the tips of the stands. Any deeper and it would indeed short on the pots. What would be a good solution for this? I'm thinking hotglue on the stands?

Whenever I need to secure a board (or anything else inside an enclosure, really), I use double-stick foam tape.  Cut it to size and stack it as high as you need.

[EBK]

Noise is probably coming from your power supply.  I know you didn't install a battery snap, but if you can try powering this from a battery, it would be a great test.

[Boiller]

I'll have to remember to get some battery snaps on my next parts order, that does indeed seem like the elephant in the room. Specially considering I'm using a 1A wallwart powering 7 pedals.

Anyway, I've been knobbing around for the last 45 minutes, and I'm very pleased with the sounds I can get out of this. I learned alot from this project, and hopefully I'll learn more and build more, and be a part of this community!

Again, thanks for the help and suggestions! Here's a couple of pics of the unfinished "finished" box.

[duck_arse]

hello and welcome to the forum, boiler. nice cat, well dressed.

I don't want to put a crimp on your day, but I think you have a problem with your T1 and T2 voltages. T2 is a phase splitter, providing opposing-phase signals at its emitter and collector. they usually allow 1/3 of the supply voltage for each leg, so we'd expect the collector to be lower. at around 6V, and the emitter to be higher, around 3V. (the same current through the same value resistors produces the same voltage drop.) unfortunately, I don't have a circuit of that type with the voltages marked-up, so I can't deffo say what they should be.

perhaps someone with a foxx build could post their voltages. then the troubleshoot really begins.

[Boiller]

I googled a bit for working tranny voltages, I found this post that states the following voltages for a working FTM pedal:

Q1 Collector 2.2
Base 0.73
Emitter 0.16

Q2 Collector 7.5
Base 2.2
Emitter 1.6

Q3 Collector 7.28
Base 0.78
Emitter 0.21

Q4 Collector 7.63
Emitter 0.84
Base 0.26

My measurements seem to be aligned with these, and AFAIK the GGG schematic is exactly the same as the Musikding kit I assembled.

[stringsthings]

Your voltages are well within where they should be
according to the GGG foxx tone machine specs.

Very nice build!  The FTM is one of my faves.

[duck_arse]

okey-dokey. now I know. carry on and well done.

[davepedals]

Alligator clips are your friend!  They can eliminate quite a few headaches caused by overheating components. This is my go-to clip: 
http://muellerelectric.com/product-category/alligator-clips-insulators/alligator-clips-insulators-aa/

[EBK]

Hmm... ?