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Author Topic: Help with DIY Fuzz pedal  (Read 12716 times)

Paul Nelthorpe

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Help with DIY Fuzz pedal
« on: August 23, 2013, 02:46:33 AM »
hey guys, first post here, you guys seem to know your stuff.

I was wanting some help with a fuzz pedal kit I recently bought on ebay. I'm relatively new to electronics and I'm no genius in this area, but I've been really frustrated for the past few days. I built this circuitboard exactly as I was instructed, yet it doesn't work and I can't figure out why.


The guy never send me a circuit diagram, but instead, more of a literal interpretation of what it would look like. Here it is -
http://oi44.tinypic.com/9a4f1l.jpg

If that is a little hard to make out, here is my own circuit diagram that I drew up (I apologize in advance for the poor quality and clarity of the diagram, I've never drawn one before)

http://tinypic.com/r/29cmbmv/5

When the switch is off, and the effect is bypassed, the guitar sounds fine, as if it was plugged in to the amp with no alteration to the sound. When I turn the switch on, I get a really crappy result. If the potentiometer is turned all the way to the left, I get a little bit of the original signal, but it's quiet and a bit lo-fi. When I turn the potentiometer to the right, I lose sound altogether... silence.

Another thing worth mentioning is that it doesn't seem to make a difference whether the battery is plugged in or not. I've tested the battery with a voltmeter and it's definetely working and has a lot of juice. I've also tested the battery socket on a breadboard incase the socket was faulty, but the socket is working fine too.

I know this isn't a lot of information to go on, but I was hoping that some of you veterans out there might be able to narrow it down for me. Based on this information, can anybody narrow down what part (or possible parts) of my circuit is faulty/busted? I have no doubt that the circuit is set up exactly the way I was instructed, and I was very careful with my soldering, there's no globby solder bridging the strips on the board.

Once again, I know this isn't a lot of info to work with, but I have no idea where to look or what to try. It doesn't work, and I don't know what to do about it

Enzo

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Re: Help with DIY Fuzz pedal
« Reply #1 on: August 23, 2013, 03:43:53 AM »
You have a mistake on your schematic.  The picture they provided is what we call a layout - a wiring diagram.

In your schematic, the jack on the right is the input jack.  You have the tip contact wired to the battery negative,and the input coming into the ring.  That is reversed. The tip should carry the input signal and the ring contact should have the battery terminal.  If you drew it wrong, correct it.  If you wired it that way, it is wrong.   The wiring diagram does not make it clear which jack terminal is which.

Your drawing shows the volume controls as 100 ohm, while the layout says 100k.  Which did you do?  100k makes sense, 100 ohms does not.

The layout shows it built on some perf board with strips of copper.   Did you build it that way too?  On the two outside strips of copper, I see a gap in each.  Did it come with those gaps or do you have to cut them?  They need to be there.

Paul Nelthorpe

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Re: Help with DIY Fuzz pedal
« Reply #2 on: August 23, 2013, 04:36:06 AM »
You have a mistake on your schematic.  The picture they provided is what we call a layout - a wiring diagram.

In your schematic, the jack on the right is the input jack.  You have the tip contact wired to the battery negative,and the input coming into the ring.  That is reversed. The tip should carry the input signal and the ring contact should have the battery terminal.  If you drew it wrong, correct it.  If you wired it that way, it is wrong.   The wiring diagram does not make it clear which jack terminal is which.

Your drawing shows the volume controls as 100 ohm, while the layout says 100k.  Which did you do?  100k makes sense, 100 ohms does not.

The layout shows it built on some perf board with strips of copper.   Did you build it that way too?  On the two outside strips of copper, I see a gap in each.  Did it come with those gaps or do you have to cut them?  They need to be there.

The volume controls were 100k, not 100 ohm, my mistake.
Also, I definitely have the ring connected to the battery and the tip connected to the switch. I think I may have labelled it wrongly on the diagram. I always assumed the longer line was the tip and the shorter one was the ring? Is this not the case?

Also yes I did to the project on some veroboard and I drilled the holes out of the copper where the gaps needed to be. Tested it with a multimeter, there was no continuity.

What's the chance that some of the components on the board are busted? I don't know why they would be  but I'm out of ideas.

Paul Nelthorpe

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Re: Help with DIY Fuzz pedal
« Reply #3 on: August 23, 2013, 05:48:58 AM »
Ok, so based on the advice from another forum, I've done 2 things.

1. switched the direction of the diode
2. Replaced the transistor.

The replacing of the transistor seemed to do the trick, but now it doesn't make a difference which way I put the diode, which makes me think something's wrong :\

It sounds ok I guess, I pluck the string and then I get like about a second of fuzz before the note fades away into clean

Roly

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Re: Help with DIY Fuzz pedal
« Reply #4 on: August 23, 2013, 07:38:00 AM »
Hi @Paul, and welcome.

For a first circuit that ain't 'arf bad.

It doesn't help that in the diagramme you have been provided doesn't indicate the battery polarity. The negative should go to the socket, and the positive to the stripboard.

The socket wiring is also not at all clear.

The pot is the output level control so it should go quiet when turned right down.  The pot is drawn from the rear view, so you may have wired it so it works in reverse, no big deal, just not helpful when debugging.

Quote from: Paul Nelthorpe
It sounds ok I guess, I pluck the string and then I get like about a second of fuzz before the note fades away into clean

The diode should have a band around one end.  This end should go to the transistor Base and 4.7uF input cap.  If the diode were in the other way around, band to the transistor Collector and 10k resistor, then I would expect the dropout effect you are getting.

Working correctly this circuit should give you loads of graunch right down to the lowest levels from the guitar.

HTH
If you say theory and practice don't agree you haven't applied enough theory.

Paul Nelthorpe

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Re: Help with DIY Fuzz pedal
« Reply #5 on: August 23, 2013, 08:34:28 AM »
Hi @Paul, and welcome.

For a first circuit that ain't 'arf bad.

It doesn't help that in the diagramme you have been provided doesn't indicate the battery polarity. The negative should go to the socket, and the positive to the stripboard.

The socket wiring is also not at all clear.

The pot is the output level control so it should go quiet when turned right down.  The pot is drawn from the rear view, so you may have wired it so it works in reverse, no big deal, just not helpful when debugging.

Quote from: Paul Nelthorpe
It sounds ok I guess, I pluck the string and then I get like about a second of fuzz before the note fades away into clean

The diode should have a band around one end.  This end should go to the transistor Base and 4.7uF input cap.  If the diode were in the other way around, band to the transistor Collector and 10k resistor, then I would expect the dropout effect you are getting.

Working correctly this circuit should give you loads of graunch right down to the lowest levels from the guitar.

HTH

Thats super frustrating. I don't know anymore what to try. It's wired up just as in the diagrams

Enzo

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Re: Help with DIY Fuzz pedal
« Reply #6 on: August 23, 2013, 07:14:13 PM »
The jack.    Just as on a real jack, the tip contact is the farthest one from the bushing.  So the longer one would be the ring in your drawing, but would be the tip in the layout.


OK, so troubleshoot the thing.  It is a one transistor preamp.  Put your meter black probe to common - "ground."  Plug in the guitar.  Now you should see +9v to the red battery wire.  And also at the top end of the 10k resistor.

Now what voltage is at the other end of that resistor, at the collector of the transistor?

By the way, did you use an actual 2N3904?  As opposed to "something equivalent"?

Paul Nelthorpe

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Re: Help with DIY Fuzz pedal
« Reply #7 on: August 24, 2013, 12:40:53 AM »


By the way, did you use an actual 2N3904?  As opposed to "something equivalent"?

I'd be lying if I said I knew.

How do I identify the type of transistor?

Enzo

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Re: Help with DIY Fuzz pedal
« Reply #8 on: August 24, 2013, 02:41:15 AM »
Oh, you bought a kit with all the parts?  Then I will assume the part is correct.

The part number is usually printed on the flat face.

Paul Nelthorpe

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Re: Help with DIY Fuzz pedal
« Reply #9 on: August 25, 2013, 03:06:39 AM »
Oh, you bought a kit with all the parts?  Then I will assume the part is correct.

The part number is usually printed on the flat face.

I got a transistor with the kit. This however, was the faulty one. The one I replaced it with is just from a big bag of transistors I have in my drawer.

I don't think the part numbers will be the same even if they are the same transistor. The broken one was from the US, the other ones I own are all from Australia

Roly

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Re: Help with DIY Fuzz pedal
« Reply #10 on: August 25, 2013, 02:08:11 PM »
Well as it turns out I live near Ballarat, phatt's near Nambour, JM is somewhere in Brazil (feasting on incinerated cow and pickled Armadillo), and I have no idea where Enzo and JoeCool are, America I assume, but transistor type numbers are (thankfully) international and a 2N3904 is a 2N3904 wherever you are.

Another helpful thing is that just about any transistor should work in this circuit.  If your original transistor was dead the most likely reason is that you had an accident with it, and if so the diode may have suffered also.  Out of circuit the diode should test on your multimeter diode test setting as around 500-700(millivolts) in one direction, and 1____ (infinity) in the other.  If it reads infinity in both directions, or less than about 500 in either direction then it's boofed.

If you don't have a spare diode, as you have a bag of sundry transistors a quick fix is to take one of these and again using your diode test range identify two of the three leads that give a diode result.  When you have 500-700mV the lead with the black probe is the cathode or diode banded end.  Use like that and leave the other lead floating.

HTH
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

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Re: Help with DIY Fuzz pedal
« Reply #11 on: August 26, 2013, 11:01:53 AM »
correct, 2N3904 is the same everywhere.  But if you used a grab-bag transistor, it may have the wrong lead configuration.

A 2N3904 has the leads E-B-C across the front.  A 2SC954 might work in its place - in other words be equivalent - but its leads are in order E-C-B.  And a BC550 might work, but it will have yet another leg order.   A grab bag might have any or all of those and others.  ANy might work, but you have to turn the transistor around or sideways for it to fit the right legs into the holes electrically.


For the record, I am in Michigan, in the northern USA, surrounded by the Great Lakes.

Roly

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Re: Help with DIY Fuzz pedal
« Reply #12 on: August 26, 2013, 01:16:37 PM »
Quote from: Enzo
surrounded by the Great Lakes.

Sounds noice.  And lots and lots of little lakes too I see.  No pickled Armadillo I guess.   8|
If you say theory and practice don't agree you haven't applied enough theory.

Enzo

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Re: Help with DIY Fuzz pedal
« Reply #13 on: August 26, 2013, 02:03:50 PM »
Armadillo - also known as "possum on the half-shell" - would be down at the other end, in Texas.




Michigan is more into cherries, apples, potatoes, and sugar beets.   And few know, but under Detroit itself is a large salt mine.  But no armadillos...

http://www.atlasobscura.com/places/detroit-salt-mine

Kaz Kylheku

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Re: Help with DIY Fuzz pedal
« Reply #14 on: August 26, 2013, 07:23:12 PM »
ADA MP-1 Mailing ListMusic DIY Mailing List
http://www.kylheku.com/mp1http://www.kylheku.com/diy