Building a Univox Super Fuzz

[chuckfalcon]

Hi everyone!  I am trying to build a Unicord/Univox Super Fuzz straight from a schematic and I am having some difficulty.  I have breadboarded some of the projects on the beavis audio site (the ones that have a picture of the breadboarded layout).

I've built the circuit from the schematic several times and I have not got the results that I am looking for.  I either get no signal pass at all or I get signal and the pot only increases or decreases volume.

Is there a way to test the circuit, as you build it so you can know you are building it correctly after each several components that you add?

Ive been using this schematic http://freestompboxes.org/members/uzzfay/web.archive.org/web/20120313025416/http_/members.fortunecity.com/uzzfay/superfuzz1/usf.html

also this diagram:
http://freestompboxes.org/members/uzzfay/web.archive.org/web/20120313025407/http_/members.fortunecity.com/uzzfay/superfuzz1/sfbrdptmk.html

[duck_arse]

chuck - search for audio probe on tis very site. it's extemely simple to build and use, and is exactly the thing you need. once you've built it, we'll walk you through the using. the superfuzz is a perfect candidate for sectional build/test.

[chuckfalcon]

chuck - search for audio probe on tis very site. it's extemely simple to build and use, and is exactly the thing you need. once you've built it, we'll walk you through the using. the superfuzz is a perfect candidate for sectional build/test.

Thanks so much for the reply!  I still need to make an audio probe, however I was able to get the super fuzz to work!  It sounds so so good, however when I start turning the "expander" know to almost the highest point and until max, and I play more aggressive, I get this sputtered "dying battery" sound.  I've owned an original version of this pedal forever ago, and that didn't have the dying battery sound.  What in the world could it be?  It starts happening right at Transistor 3 and then through the rest of the circuit.

I used this schematic:
http://freestompboxes.org/members/uzzfay/web.archive.org/web/20120313025407/http_/members.fortunecity.com/uzzfay/superfuzz1/sfbrdptmk.html

[smallbearelec]

I get this sputtered "dying battery" sound...It starts happening right at Transistor 3

So you have an original pedal? Cool! One thing that would be really useful, both to you and to other prospective builders, would be a list of voltages at C, B and E of each transistor. When all of the devices are biased correctly, it shows up in the pedal sounding "right". Between using an audio probe to isolate where the signal is getting corrupted, and voltage measurements compared with a working circuit, you'll know where to fish for your problem.

[duck_arse]

to add to what the bear says, because of all the biasing resistors involved in the superfuzz, the voltages around the transistors are fairly rigidly defined. unlike the muff, eg, it relies less on the transistor characteristics to set operating points.

[chuckfalcon]

I get this sputtered "dying battery" sound...It starts happening right at Transistor 3

So you have an original pedal? Cool!

I used to have the pedal    it was a great one.  I was out of town today so I wasn't able to start debugging but one thing that would probably be good to mention is that from the schematic and the layout, there is a 10uf cap that goes on the power rails.  Im not really sure where to put it, I have tried it several places in the circuit, even RIGHT after the 9v battery.  The pedal functions exactly the same if the cap is in the circuit or not.  Perhaps I am inserting it in the wrong place at that is what is causing my woes.  Any thoughts?

[duck_arse]

that, being a supply bypass cap, can go anywhere, as long as its positive lead is connect to the +9V line (anywhere on the board) and its neg lead goes to the earth/ground/0V/- line (anywhere on the board). obviously, the best place for it is where it fits, and connects, without having its leads stretched and bent all over. it is meant to keep the supply lines clean of AC garbage. it is unlikely you will hear any effect when battery powered.

[chuckfalcon]

Ah ha!   Thanks for the quick reply! 

How do I go about testing the voltages of the base, collector, and emitter? 

I have a DMM.  I haven't tried to make an audio probe yet.  When I plug the output of the circuit into the base of Q3, and turn the expander pot all the way up, I don't get dying battery sputters, its not until I plug the output into the collector or the emitter from Q3 and then on I get the sputters, so I am guessing I am having some voltage issues with my Q3.  I have checked orientations and chances of shorting, nothing just yet, but there is no way I'm throwing in the towel.

[duck_arse]

how to do measures: set yr dmm on DC volts, lowish range (mine is autoranging, so I don't know what common ranges are, maybe 10V?). put your black lead to the ground//0V connection, to provide the reference for your voltage-ings. now proble the red to each of the transistor leads, making sure you know which lead is which. we get peeves when people mix their E with their C. then you come here and type something like:

Q3 E= 3V, B= 3V6, C= 6V

(for each of the transistors won't hurt) and in your case, we want you to do expander full cw voltages, then full ccw voltages. and, if you feel like looking up ohm's law, and you will at some stage have to, you might even be able to spot any wrongs yourself.

and it sounds like we want to see your volts around the Q4//Q5 pair too. check the 2 10uF caps to their bases .....

[edit :] silly me, meter ranges will be 2something. 2.00V, 20.0V, 200V, have been since the dawn of the lcd.

[chuckfalcon]

how to do measures: set yr dmm on DC volts, lowish range (mine is autoranging, so I don't know what common ranges are, maybe 10V?). put your black lead to the ground//0V connection, to provide the reference for your voltage-ings. now proble the red to each of the transistor leads, making sure you know which lead is which. we get peeves when people mix their E with their C. then you come here and type something like:

Q3 E= 3V, B= 3V6, C= 6V

Ok, I probed every transistor, first with the pots turned all the way cw, then all the way ccw.  I think I must have measured incorrectly because I got basically the exact same readings.  The 9v battery was plugged into the circuit (power rail)  and I put the black probe on the black wire (negative) that was inserted into the (-) hole, and then I used the red probe and individually touched each leg of each transistor and this is what I got:

Q1: B=.015 C=8.34 E=.029

Q2: B=8.34 C=8.32 E=7.68

Q3: B=.729 C=.135 E=.151

Q4: B=1.495 C=3.387 E=.907

Q5: B=1.496 C=3.382 E=.908

Q6: B=1.087 C=3.698 E=.477

That's what I got, but I am not sure if I tested correctly.  Did I test in the right place?  is the battery supposed to be plugged in?

[duck_arse]

there's a problem there somewhere. you do need something providing the transistor supply volts, either a battery or an external 9V DC supply.

Q2 looks as though B and C are short circuit. can you test (supply OFF) resistance/continuity there? check the 47k to V+ at the base, as well.

did you have supply volts when you measured, because Q3 looks disconnected? measure right along the V+/9V line, make sure you have the full battery volts at the top of all the parts connecting to that line. Q4 and Q5 and Q6 appear about right, so something is screwy up the front end.

[edit :] you're still on the breadboard, is that right? and if so, it looks like you may need some links along your supply busses, many BB's have disjointed outer rails. can we see a pic of your board?

[chuckfalcon]

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[chuckfalcon]

[duck_arse]

photobucket.

well, the picture answers that question, and another I was going to ask.

the breadboard is a wonderful thing, because you can pull things down and build other things with the same parts. I'd suggest you pull that board down, and use the parts to build the modified fuzzface around Q1 and Q2 first, from the input resistor up to and including the expander pot. switch that on, see if it works, get some voltages.

when it does work, you can then build a phase splitter, from the 10uF on the expander through to Q3 E and C resistors. power that up, see if your voltages are right, then connect it to the expander pot. check you volts, it's gotta still be working, right?

then find some clear space and throw o the differential pair, Q4 and Q5, with all their base resistors and the emitter and collector parts, power it, see if the right volts appear. then you can add the 10uF caps and series 470R from the bases to the phase splitter, see what.

when that works, and stays working, add the clipping diodes and their 10uF's, and the notching parts that follow, up to and including the balance pot. if you don't get some audio probed signal on the wiper there, find out why not, otherwise, build the single satge amplifier at Q6. check its volts, add the 10uF at the base, and you have a working superfuzz.

but pull it apart and do it in sections.

[chuckfalcon]

I tested the Base and the Collector of Q2, no beeps coming from the DMM.

The 47k to +V seems ok.   I have that one connected like this: Q1 collector, wire from Base of Q2 going to Q1C rail, 47k resistor to +V

I know the picture looks like a jungle and is kinda hard to decipher but it starts on the bottom left then to the right, and then at Q3 I moved the circuit to the top left and when right just because I figured that I would run out of room.  

Thanks for your help so far.  I have the next several days off, so I am going to try and rebuild the first half of the circuit and see where it takes me.  Also, is there a better way to do this?  Like a not as confined confusing looking breadboard?  This is pretty nuts, haha.

[chuckfalcon]

photobucket.

well, the picture answers that question, and another I was going to ask.

Okie doke.  Thanks for all of your time so far.  I'm about to tear this thing down and start from the top again and go by sections.  When I go for voltages, what are the numbers that I am looking for that would be considered "correct"?  Does it vary between pedal to pedal?  Do you know the correct specific voltages for the Univox Superfuzz?

[twabelljr]

GGG voltage guidelines:

http://generalguitargadgets.com/pdf/ggg_superfuzz_instruct.pdf

[chuckfalcon]

GGG voltage guidelines:

http://generalguitargadgets.com/pdf/ggg_superfuzz_instruct.pdf

AWESOME!  Thank you so much.  One question though, will those same voltages apply even though I used different transistors?  I used 2SC828's and this link used 2N2222A's.  Maybe those tranny's are equivalents, I'm not sure.

[duck_arse]

chuck - I was going to ask you about your transistors, specifically the two with the yellow jumper top left. can you point me to the datasheet you're using for those parts? I can't see a sensible "t092-b" pinout.

and the goodest thing about the superfuzz is all those bias resistors, which tell the base of each transistors what to do. the E and C voltages follow from there, so the transistor specs, to a very large extent, are irrelevent to the circuit voltages. give or take, and not so much for Q1 and Q2, which interact and settle to a point they are happy with.

2222's will be much the same as 828's for our purposes.

[chuckfalcon]

chuck - I was going to ask you about your transistors, specifically the two with the yellow jumper top left. can you point me to the datasheet you're using for those parts? I can't see a sensible "t092-b" pinout.

Here is that data sheet I was using http://alltransistors.com/pdfview.php?doc=2sc828.pdf&dire=_no

The only reason I was using that transistor is because that is what the schematic called for and I was just trying to get the exact sound that I remember hearing from my old Super Fuzz.  Man it sounded gnarly and delicious.

Those  2 transistors with the yellow jumper that you are talking about are Q4 and Q5.  In the schematic, it looked like their collectors are touching so I jumpered them.

As far as bias resistors go.  How can you determine which resistors are bias resistors?  Is it always the one attached to the base and then connected to either (-) or (+)?