Tonefiend Forum

Let us see if I can open this topic up and have it silent forevermore? Anyway I did a breadboard twice and had it where I wanted it to be.I did my first ever perfboard and had a few screwups that caused a restart with all new parts. Got to the end of the second try and when I hooked it up to the breadboard to test I get a signal of clean guitar no distortion. I have been testing it for continuity and found out if you lay the tester across both buses you fry the LED (twice). Can you destroy all the various parts (transistors,caps,resistors) ? Does power have to be turned on for it to test properly, not getting a signal from the postive bus from the transistor? Will figure out how to get some pics on here for further inspection. It ain’t pretty so be prepared , I am on my first project that isn’t a PCB and I probably shouldn’t be touching a soldering iron or electrical circuits. BTW I am still dreading the actual stuffing into a box and footswitch connecting .

I know I’m a few years late to the party, but… I just breadboarded project #1 (Bad-Ass Distortion) and like Oinkus, I’m getting a clean signal – NO DISTORTION. Any idea how to dirty up the sound – a.k.a. what did I do wrong?

I just checked for continuity between adjacent components – all good. I checked resistors using multimeter – all good. Not sure how to test caps, so I’m not sure about them. I double checked that the battery had life – yup. Lastly, carefully and in order of the build, unplugged each component from the breadboard and reinserted, making sure I had a good connection, and again checked continuity between adjacent components – I did. STILL only a clean sound, NO DISTORTION!?! Please help.

That circuit is pretty straightforward. The fact that you get SOMETHING is promising. If you unplug the battery and get NOTHING, that would tend to indicate that the transistor is at least working.

The thing that I would suspect more than anything else is maybe you have used a 470K where it says 470R. 470R means 470 ohms, whereas 470k means 470,000 ohms. Could you please write down the color bands for the resistors? The 470-whatever will start with yellow, violet, then something else #1 and probably something else two. Also note the markings on the caps. What are they?

The other thing I suspect is if you take the output from the emitter rather than the collector, then you won’t get any gain. It will not harm anything to connect the output cap to the “other” lead to check this.

The other other thing it might be is the transistor is backwards, putting C where E should be and vice versa.

Here’s a color code to resistance calculator (don’t trust my memory)…

https://en.wikipedia.org/wiki/Electronic_color_code

I’m somewhat confused by your color bands… are these 1% resistors? I’d expect a 5th band for tolerance, but let’s move along…

Let’s just map it out anyway…
Let’s suppose the final band is the number of extra zeros…

470R is yellow (4), violet (7), black (0), black(0). => 470 (zero extra zeroes)
2.2M is red (2), red (2), black (0), yellow (4) => 2,200,000 (4 extra zeroes)
68k is blue (6), silver (probably grey) (8), black (0), red (2) => 68,000 (2 extra zeroes)

So those values do look correct.

If you have a voltmeter which can read ohms, it would be good to double check these values.

Next let’s look at the currents flowing in the circuit.

I(R2) => (9.44 – 1.44)/68000 = 0.000117647
I(R1) => (1.44 – 0.61)/2,200,000 = 0.000000377
I(R3) => (0.05 – 0)/470 = 0.000106383

It doesn’t quite add up, but the 0.05 reading isn’t very accurate, so I shouldn’t add more units of precision than are really called for. I’ll conclude that these values are reasonable. What I was looking for was I(R2) = I(R1) + I(R3). The current in R2 goes into the collector and the base (via R1). The current coming out of the emitter should be the sum of the base and collector currents. I don’t see anything obviously wrong here.

The ratio of the collector current to base current is I(R2)/I(r1) which comes out to about 312. I think this is a reasonable value for a 2N3904 (but I didn’t look it up).

Up to now this has all been fairly precise. Now I’m just going to guess.

See if reducing the value of R1 to 1.0 Meg makes any difference. That will increase the base current which will increase the collector current too. It may also saturate the transistor (Vce going to about 0.3 volts), but since this circuit is supposed to generate distortion I am not going to worry about that.

I don’t have any specific experience with this circuit. If we don’t get somewhere soon I may just breadboard it myself (now where is all that stuff)…

Looked at your breadboard photos. Don’t see anything obviously wrong there.

What are you running this into to listen to it? A small load (anything much less than 68k) will reduce the gain. This circuit has tons of gain but for example if you ran it into an 8 ohm speaker, the gain would be greatly reduced.

So, 8 minutes later I plug the transistor back and figured out I am a complete idiot. The reason all the math worked out and I was sure that I put it together properly was because… I did, except the volume on my guitar was at 4 instead of ten. I turned up my guitar volume and strummed two heavily distorted chords.
I will chalk it up as my first of many super newbie mistakes. Besides even that little bit of math for current differences that you showed me really gave me something to think about and chew on.

Thanks a lot man! Happy tinkering.