Problems with Fuzz Face BC108

[khm9]

Hello, today I've built my first fuzz face circuit. I have etched a board, soldered on components, now unfortunately i do not have in/out jacks, so I cannot test if sound comes out of the circuit.

This is the original schematic


Now, since I wanted to build BC108 Fuzz Faze, I've done some modifications to the circuit (changed polarity of the 2 caps and transistors).
this is what I have built:


Original BC108 circuit is:


Now my questions are:
1. Will this work?
2. noob question: where do I measure voltages? what needs to be measured and how?

This probably doesn't work anyway, it never does first time

Layout I used:


As I have said, changed the polarity of the 2 caps and transistors, rest is left same.

I can also take a few pictures of the board if needed.

P.S. This is kind of my first build, so please bear with me

[khm9]

Okay, I think I got the measuring part.

So basically to measure a voltage put the black wire from multimeter to ground in the circuit and with red wire measure the more complicated parts in circuit?

[khm9]

Okay I have "measured" transistor voltages. Not sure if they're good

Battery: 8.83v

Q1: C: 1.31; B: 0.59; E: 0.
Q2: C: 2.53; B: 1.31; E: 0.68.

I have used 470ohm resistor instead of original 330ohm.

Tomorrow I will buy in and out jacks and test if sound comes out of this thing.

[dbp512]

Wouldn't the BC108 need +9 volts, instead of the -9 you listed? Its an NPN transistor, not PNP like the first schematic. Although you said you're using a battery, which is positive voltage anyway. You don't want to get those confused, or bad things happen to your components. Your precious silicon doesn't like the wrong kinda juice.

[PRR]

Those voltages are close-enough to work.

Also close-enough to suggest it isn't reverse-polarity. I think that is just a leftover of the drawing conversion.

> battery, which is positive voltage

Battery has no idea where "ground" is. Yes, in cars the recent fad is Positive HOT. However a 1941 Plymouth (and many cars of the period) is Negative HOT. Negative ground cars is largely a side-effect of a car-radio fad that only lasted a few years; cars (and batteries in general) can be put any which way the devices like to see it.

[dbp512]

Paul, I learn something new every time you type something out

[khm9]

Hi all, today was the worst day in my short stomp box building life.

Well first of all, I managed to get bypassed sound with a 3pdt switch, the problem was once it was on, i still got bypassed sound (little bit darker, but still clean).
LED did not light at all (even though i tested it, works fine when fed with 9v directly) stereo jack i bought was low quality so i threw it away, and that's what probably screwed me up.
I wired 3pdt great itself, but around jacks, i think i screwed a bit.

I forgot to modify the schematic up there, I did feed +9V to the circuit yesterday and I got
Q1: C: 1.31; B: 0.59; E: 0.
Q2: C: 2.53; B: 1.31; E: 0.68.

Out of curiosity I changed the polarity and got quite different voltages, like on
Q2: c: ~5.04; b: ~4.5; e: ..dont remeber emitter voltage, but it was higher than 0.68.

I just want to get this thing working, so I can be sure the circuit is not the problem, then later i can add a 3pdt.

Can someone please give me a wiring diagram for without a 3pdt?

p.s. can i kill the transistors by doing this??

[smallbearelec]

I agree with Paul that the voltages look like the circuit should work, so we'll guess that the stomp switch is not wired right. Disconnect that. Now check out my tutorial:

http://diystompboxes.com/barebonesfuzzface/

Scroll down to Figure 108, and you'll see pics there of how to ID Tip, Ring and Sleeve of standard jacks. Input jack Tip goes to Input on your board. Output jack Tip goes to the center (wiper) contact of the Level pot. Sleeves of both jacks go to GND. Connect battery and see if you get fuzz. If that works, we can talk about wiring stomper and power.

BTW: I would not have advised etching a board for your first build. However, from the voltage measurements, it appears that you succeeded. I also would have recommended that you breadboard first.

http://diy.smallbearelec.com/HowTos/BreadboardSiFF/BreadboardSiFF.htm

and I would still recommend that you back up and learn how to do that before your next soldered build. There is a learning curve to this hobby, and starting too high on the curve leads to frustration when the climber drops off and hits bottom.

[khm9]

Thank you smallbearelec, your guide is very useful, I wired everything as you said and I don't get any sound out of it...

I noticed that when I put my finger (or multimeter) on top of the Q2 transistor or on the collector, I get the high-pitched hiss out of the amplifier (voltages remain same). Voltage (~2.5v) is the same on top of the transistor and collector, so I guess collector and top of the transistor is the same thing.

Similar thing happens with Q1 but you can hardly hear the hiss.

I really don't know guys what's wrong with this circuit, my guess would be the transistors.

I have taken some close up pictures with values for you, so you might see what's wrong here. Thank you.

[Cozybuilder]

Check that your in and out wires are going to the tip, not the ring. Use a multimeter to verify which tab on the jack goes to the ring, and which goes to the tip.

[LightSoundGeometry]

for what s its worth I have had voltages and branded xxxxx in fuzz circuits and some will not work while others will.

with that said, what can I do with trannies in the 30-35 hfe range ? lol

[khm9]

Check that your in and out wires are going to the tip, not the ring. Use a multimeter to verify which tab on the jack goes to the ring, and which goes to the tip.

I tested it, the lug i soldered on the in and out wires shows connectivity on one more lug which is also connected to the tip (so there are two tips and one ring?). I will go ahead and solder in and out wires to that another lug, can't hurt to try.

I will let you know if it works in 10 minutes.

[khm9]

OK GUYS

IT WORKS thanks to

Check that your in and out wires are going to the tip, not the ring. Use a multimeter to verify which tab on the jack goes to the ring, and which goes to the tip.

All I done is this, soldered to another lug, both for in and out.


No more hiss when touching transistors 

I am really happy thanks 

Just one little problem, on gain pot when turned on full I get a insane hiss (sound still comes), then when I just move it a little bit back, hiss is completely gone! Is this a faulty pot?

[Cozybuilder]

Glad you got it working 

For the hiss, try a small cap (maybe 22 to 47pF) across the Q2 BC legs.

[smallbearelec]

gain pot when turned on full I get a insane hiss (sound still comes)...Is this a faulty pot?

This is your first and most important lesson: When a build from a familiar schem does not work, it's Rarely because a component is bad. It's almost always a wiring problem or something that you don't know yet about how the circuit works. In this case, I think the issue is that you are using two fairly high-gain transistors, and the circuit is going into oscillation when the gain pot is fully clockwise. Notice that the layout in my tutorial (Fig. 65) includes places for two small capacitors, CX1 and CX2,  (100 to 200 pf.) from C to B. Fixing this problem is what they do; you might only need one of them.

You started waaay higher on the learning curve than I would have suggested, and you survived...Congratulations! Now that you can properly ID the terminals on your jacks, thanks to Cozybuilder, back up, get a breadboard and try optimizing the build as I show in my breadboard tutorial. Especially, try a lower gain device for Q1 and then adjust the bias resistor values for smoother clipping and reduced harshness. If you can get a 1K reverse-audio taper pot for the gain, you'll find that the control of fuzz is much smoother. When you have something happy-making, either make another board or re-use the one you have. Then you are ready to go from breadboard to box. You have proven that you can make a good board; give the same care to the mechanical layout of the enclosure. The board layout looks like it leaves you enough room to bore two holes for standoffs. My second tutorial shows some good practices for connecting power and stomp switch, and I hope it helps you assemble and wire.

Regards
SD

[khm9]

Thank you guys!

I will solder a cap tomorrow.

Yes I agree with you smallbearelec. I started way higher on the learning curve, I should've learned to use breadboard first, which i still don't
But I will, its important for things like these and customizing an effect.

And as for the project itself I don't know any simpler effect than fuzzface or you think I should've gotten a kit?
Well I am a big hater of kits. It feels like cheating.

After this I feel I could build a big muff 
even though I'd probably get stuck with a wiring problem

P.S. I am playing around with LED's. I've put 47ohm resistor and it's ok, quite bright, what concerns me is that it gets REALLY hot, probably since resistance is really small. I think I should increase the resistance? Could you recommend me a way on how to find a good spot and what resistance should i play around with? 47ohm is quite low...

[PRR]

> it gets REALLY hot

Learn Ohms Law and use it relentlessly.

> LED's. I've put 47ohm resistor

You don't say what LED or what battery. I will assume 9V batt and the LED takes so much voltage that 4.7V is left on the 47 Ohms resistor (makes the math easy). Then 4.7V across 47r is 4.7/47 or 1/10 Amps, or 100 milliAmps.

The spec MAX on most small LEDs is 20mA.

> it gets REALLY hot

Say you have a plow-tractor rated 20 HP. And somehow you get it to do 100 HP of work. Yeah, it'll get hot.

FWIW, LED resistors for stage pedals often use resistors with a "K" in the value. We aren't trying to light the whole stage. 4.7K, about 1mA, is often ample to tell you off/on.

[khm9]

Thanks Paul,

Yes 9V battery, I should've been more specific, sorry.

Below are the LED's specs...

Manufacturer: KENTO
Manufacturer Part No: 5408URC
Illumination Color: Red
Lens Color/Style: Red
LED Size: 5mm
Lens Shape: Round
Wavelength/Color Temperature: 620-630nm
Luminous Intensity: 8000 - 10000 mcd
Viewing Angle: 30 deg
Forward Voltage: 1.9 - 2.1 V
Forward Current: 20mA
Maximum Operating Temperature: + 100 C
Minimum Operating Temperature: - 20 C

[smallbearelec]

I don't know any simpler effect than fuzzface or you think I should've gotten a kit?

Usually, I suggest breadboarding a one-stage boost for a first build. There are many, and some are quite useful. You made the FF to work, and fine. You did it with silicon rather than germanium, which was the right thing for a first build. Kits have their place, though I agree that many are too paint-by-number.

After this I feel I could build a big muff even though I'd probably get stuck with a wiring problem

If you do this, find a vetted layout. It's a good circuit to build one stage at a time, testing after you finish each stage.

P.S. I am playing around with LED's. I've put 47ohm resistor and it's ok, quite bright, what concerns me is that it gets REALLY hot

47 ohms is waaay too low. That LED is a high-brightness type, and it should give you adequate visibility with a series resistor of 8 to 10K at 9 volts.

[PRR]

> Forward Voltage: 1.9 - 2.1 V
Forward Current: 20mA

There you go.

The LED is around 2V drop. You have 9V. Difference to be lost in a resistor is 7V.

MAX current is 20mA. 7V/20mA is 350 Ohms. That is the SMALLEST safe resistor. (370 Ohms accounting for a hot battery and a lo-V LED.) Or, knowing that you CAN run an LED at any lower current (with less light), you might do easy-math: 7V/14mA is 500 Ohms, 7V/7mA is 1K ohms.

From experience, you can't tell the difference 20mA or 14mA unless you have them side by side. The eye is not that critical of light intensity.

In the Old Days, we did have to throw 10mA into an LED to be visible in classroom light. 3mA might have been fine on stage. But LED efficiency has gone up a LOT over the years. I said 4.7K, Bear says to 10K; but certainly up in the "K"-zone, not 47 Ohms (0.047K).