Help with DIY Fuzz pedal

[paulnelthorpe]

 

hey guys, first post here, you guys seem to know your ****.

 

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

[Kazinator]

Did someone sell you a generic piece of strip board that you can buy anywhere and call it a kit? Does the kit include an enclosure to complete the build of this stomp box, or is it just over-the-counter electronic parts and a diagram?

Your schematic looks good for the most part. But there is a glaring mistake in the hookup of the jacks and the bypass switch.   The DPDT switch switches the signal (coming from the tip of the jack). You have it hooked up to ground (the sleeve).

The grounds should always be connected: regardless of the position of the switch, the sleeves of the input and output jacks are connected to the ground network. The switch acts very much like a pair of railway switches: it either connects the input and output jack to the circuit, or it connects them to a bypass "railway" (which is just the two bridged terminals on the switch).  The basic idea is this:

 

              *------[ through circuit ]---*             /                              \nO---IN------*                                *---OUT---O              *---------[ bypass ]---------*O-------------------------[GND]------------------------O

The input jack is stereo, which is a trick to turn on the circuit. When the plug is inserted, because it is a mono plug, it bridges together the middle ring and the grounded sleeve. This common trick is used as the basis of a ground-side power switch. That is to say, the circuit board's ground connection goes to the input jack's ring. When the plug is removed, the ring is thereby disconnected from ground, and the circuit board loses power. Once you understand this, it will be obvious how to hook it up.

If you're not sure which lugs on the jack correspond to the tip, ring and sleeve, use your multimeter to check continuity.

You should install a power switch in addition to this switching mechanism, because you don't want to go through the hassle and jack/plug wear of unplugging from the stomp-box just to turn it off!

 

[Kazinator]

There are better sites for DIY stompbox discussions and questions.

I like ssguitar.com.  It's fairly quiet these days, but it has a handful of people who know their stuff and questions get prompt answers. This would be topical in the Newcomer's Forum as well as the Preamps and Effects one.

A solid question with specific points and a schematic should be received well by the Q&A site electronics.stackexchange.com.

 

[Kazinator]

By the way, there are several white squares over the strip board in the diagram. These  mean that you must divide the strip at that point. Did the "kit" maker prepare that for you, or is it a blank, original stripboard?

For instance, if you do not cut the bottom strip, then the circuit board simply shorts the input to ground! The left portion of that strip is used for the input network, and the right portion is ground. These must be cut apart, and verified not to have continuity.  Similarly, the upper strip contains both the positive power rail, and the output from the transistor stage to the potentiometer, and must be cut as indicated by the white square if this is not already done.

 

[paulnelthorpe]

 

---

Kazinator wrote:

 

Did someone sell you a generic piece of strip board that you can buy anywhere and call it a kit? Does the kit include an enclosure to complete the build of this stomp box, or is it just over-the-counter electronic parts and a diagram?

 

Your schematic looks good for the most part. But there is a glaring mistake in the hookup of the jacks and the bypass switch.   The DPDT switch switches the signal (coming from the tip of the jack). You have it hooked up to ground (the sleeve).

 

The grounds should always be connected: regardless of the position of the switch, the sleeves of the input and output jacks are connected to the ground network. The switch acts very much like a pair of railway switches: it either connects the input and output jack to the circuit, or it connects them to a bypass "railway" (which is just the two bridged terminals on the switch).  The basic idea is this:

 

 

              *------[ through circuit ]---*             /                              \nO---IN------*                                *---OUT---O              *---------[ bypass ]---------*O-------------------------[GND]------------------------O

 

The input jack is stereo, which is a trick to turn on the circuit. When the plug is inserted, because it is a mono plug, it bridges together the middle ring and the grounded sleeve. This common trick is used as the basis of a ground-side power switch. That is to say, the circuit board's ground connection goes to the input jack's ring. When the plug is removed, the ring is thereby disconnected from ground, and the circuit board loses power. Once you understand this, it will be obvious how to hook it up.

 

If you're not sure which lugs on the jack correspond to the tip, ring and sleeve, use your multimeter to check continuity.

 

You should install a power switch in addition to this switching mechanism, because you don't want to go through the hassle and jack/plug wear of unplugging from the stomp-box just to turn it off!

 

 

---

 

I searched through ebay to find the top seller that I could. His kit came with a chickenhead knob and an enclosure. 

I just realised I majorly screwed up the diagram. The sleeves actually are both connected to ground, and the tips both go to either side of the DPDT switch, still doesn't work : 

Remember, the signal is fine when the switch is on bypass.

I would put a switch in there, but after I get it working and I put it in the enclosure I'm replacing the battery socket with a female barrel plug so it will just turn on and off with the rest of my pedalboard.

Here's a fixed version of the diagram - http://tinypic.com/r/29cmbmv/5