Farty Hipster Fuzz

[Kylianvb]

Hey y'all! I haven't been at this pedal-building game for too long, but have already achieved some wonderful sounds through piggybacking off of Madbean's engineering prowess. (Tonebender already done & the Afterlife Compressor ready to box up, gorgeous stuff) ... This time, however, I'm getting a farty, gated sound out of the Hipster Fuzz, and the bias isn't even getting close to what it's supposed to be. To get a proper note out of the fuzz you have to hit the string rather hard, after which the sound dies down very quickly. I've been reflowin', measurin', readin' and audio-probin' for days now, and am ready to give myself over to the expertise of people who actually know what they're doing, which is where you hopefully come in!

I used 2 2n3904 transistors, a 20k trimpot instead of a 25k one, and when this 'farty' issue persisted I eventually swapped out R4 for a 1K resistor, as the manual suggested for 'more output'... Which obviously wasn't exactly my problem, but in my desperation I figured it was worth a shot; Either way, it didn't have any positive or adverse effects to the tone from what I could tell.

The bypass is absolutely clear, and using the audio-probe I can follow the signal around the board. Drastic tone-changes obviously occur around the transistors, but I don't have the ear yet to really hear where it goes wrong.

Aaand the measurements;
9v+ = 8.52
GR = 0
Q1 = 0, 0.56, 1.26 (E,B,C)
Q2 = 0.6, 1.26, 0.62 (E,B,C)
TP= 0.62
Hopefully I got those last ones right, as far as the pinout goes... To be completely certain y'all know what I'm measuring; Looking at the PCB in the PDF, I measured from down to up. (pins 1, 2, 3 consecutively if I'm reading the datasheet right)

I'm hoping this + the attached pictures cover all the info needed and would like to thank you guys already for checking this out .

[EBK]

I'm actually a little disappointed to find out that "Farty Hipster Fuzz" isn't the actual pedal name. That would've been awesome. 

[midwayfair]

Does your test point voltage change when you rotate the trimmer?

[Kylianvb]

I'm actually a little disappointed to find out that "Farty Hipster Fuzz" isn't the actual pedal name. That would've been awesome. 

Aww man, too bad I've already prepared my enclosure for this goofy design... Well, let's put that one on the to-do list!

Does your test point voltage change when you rotate the trimmer?

Yes indeed, the measurement above is the trimpot at its max value. When turned the volume pretty quickly goes out completely. The "end-value" when completely turned to the other side is 0.47.

[zombie_rock123]

It looks like you've socketed the transistors with short leads and then soldered in to the sockets. Great practice that I learnt from this forum but did you test before you soldered them in? I've fried a few that way.

[Kylianvb]

It looks like you've socketed the transistors with short leads and then soldered in to the sockets. Great practice that I learnt from this forum but did you test before you soldered them in? I've fried a few that way.

The results were similar before soldering them in, which I then did because I figured there might be a loose lead when they were just socketed. Since I was also wondering if I had perhaps ruined a transistor, I later pulled out Q1 (including the sockets, boy what a hassle), and tested it in a little component-testcircuit I've bought. I didn't write down the readout, but it did show it as a functional NPN. Should I check the same with Q2 perhaps?

[zombie_rock123]

Yeah solder sucking or braiding is a PITA.

I wouldn't pull the other transistor yet. When you audioprobed, did you audioprobe the output pad to see if you get fuzzy goodness there and see if it was the switch that's the problem? The only other thing (I'm probably pissing people off by guessing here) but your ground pad on the row of pads on the bottom of the board may need reflowing but you said you already.

[Kylianvb]

Yeah solder sucking or braiding is a PITA.

I wouldn't pull the other transistor yet. When you audioprobed, did you audioprobe the output pad to see if you get fuzzy goodness there and see if it was the switch that's the problem? The only other thing (I'm probably pissing people off by guessing here) but your ground pad on the row of pads on the bottom of the board may need reflowing but you said you already.

The output pad is consistent with what I'm getting out of the output-jack (consistently crappy! ). From my continuity-readings the ground seems to connect to the switch well, but I'll definitely touch that up; it could be a prettier joint either way .

[midwayfair]

His transistors are oriented correctly.

Desolder one end of R4 and R5 from the PCB and measure them with your DMM.

Measure the actual resistance from pins 1 and 2 of your trimpot.

[Kylianvb]

His transistors are oriented correctly.

Desolder one end of R4 and R5 from the PCB and measure them with your DMM.

Measure the actual resistance from pins 1 and 2 of your trimpot.

Alrighty, forgive me for over-explaining my methods, but I want to be certain I'm doing these right, because I'm fairly certain I did some things wrong already ;

I'm thinking the first reading I did here, I did something whacky. The readouts I've written down for the trimpot were 0 to -2.96. Now I know I set my DMM to 20k ohm mode, but I presume I probed the wrong pins at the time. Still figured I'd include it here, something might be gleamed from it. 

At the time I was satisfied with my reading, so proceeded to half-disconnect the resistors and measure them;
R5=9.92
R4=9.93

At this point I measured the trimpot again (black testlead to pin 1, red to pin 2), and came to 19.02 - 0 when turned, which seemed like a much more reasonable readout for a 20k pot than what I started with... So I came to the conclusion I probably mucked the reading up the first time. I resoldered the resistors R4 and R5, to properly measure the 'original state'. The connection at R4 isn't perfect right now, but since I'm messing with it so much I took a reading of 8.85 for a 10k resistor as 'good enough' for the moment, since I'm a little scared of heat-damaging parts at this point.

Now with the board back to its original state, I re-measured the trimpot and came to 19.01-0. Just to be sure it was really pretty much back to its original state, I checked the TP, which indeed was at 0.62.

Sorry for this convoluted mess of a post, but I figured I should go through my actions chronologically for clarity's sake. Just checked the sound again by the way, farty as ever! Not much has changed, but I'm just glad I haven't killed the board yet.

Also, thanks for the quick responses everyone!

[midwayfair]

You need to put units in with those numbers.

Resistance is measured in Ohms. Measure your resistors in Ohms. If it's kiliohms, use, for example, 10K. If it's megaOhms, use for example 1M. When you measure the resistance across a resistor, you put the probes of your DMM on the legs of the resistor. You often have to remove one end of the resistor from the PCB to avoid accidentally measuring parallel resistance or a board failure of some sort.

If you are posting a measurement in volts, use V, or mV if the voltage is very small. Your DMM will tell you the units.

I'm not saying this to scold you but because otherwise it's impossible to help, or we might give the wrong advice.

I'm asking you to measure the resistors because your voltage is correct on the first two transistors but the collector of Q2 is too low, which can happen if the resistance is far too high.

Once you've established what the units are for your R4 and R5, look at the build document, specifically at the schematic, and tell me: Does your reading match what those resistors' values are supposed to be?

[Kylianvb]

You need to put units in with those numbers.

Resistance is measured in Ohms. Measure your resistors in Ohms. If it's kiliohms, use, for example, 10K. If it's megaOhms, use for example 1M. When you measure the resistance across a resistor, you put the probes of your DMM on the legs of the resistor. You often have to remove one end of the resistor from the PCB to avoid accidentally measuring parallel resistance or a board failure of some sort.

If you are posting a measurement in volts, use V, or mV if the voltage is very small. Your DMM will tell you the units.

I'm not saying this to scold you but because otherwise it's impossible to help, or we might give the wrong advice.

I'm asking you to measure the resistors because your voltage is correct on the first two transistors but the collector of Q2 is too low, which can happen if the resistance is far too high.

Once you've established what the units are for your R4 and R5, look at the build document, specifically at the schematic, and tell me: Does your reading match what those resistors' values are supposed to be?

Really appreciate your help, and I think you may have uncovered the problem here;
I measured the resistors in the mode labeled as '20k Ohm', which would lead me to believe that
R5=9.92 kOhm
R4=9.93 kOhm
Which would lead me to think these are 10k resistors rather than 1k resistors. If I'm grasping this correctly, that's further proven by the fact that the "2000 ohm" setting gives no read-out due to the value exceeding its limits. I was ready to scold myself HARD for grabbing the wrong bag of resistors, yet that doesn't seem to be the complete story. I've kept all resistors I've ordered in their respective baggies, and now see that my baggie of "10k ohm resistors" reads out roughly the same values as my baggie of "1k ohm resistors", that value being 10k.

.... Well, I believe this may have solved my issues (though I apparently have no 1k resistors to fix it up at the moment ), though I'd love some confirmation. Supplier error combined with me not being thorough enough in double-checking values and color-codes. I obviously didn't expect their labels to be wrong, but it goes to show ya have to double-check everything yourself.

edit:
I just rechecked the schematic for the Afterlife, which contained no 1k resistors & worked perfectly... And then the Tonebender, which didn't bias quite right and resulted in a rather compressed sound. It wasn't to the degree of this effect, and was a pretty enjoyable sound in my opinion, but now that also has been explained, there was also a supposed '1k' in there! I think I'll open that baby up once I get some legit 1k resistors in as well!