Mantle Fuzz (MXR Blue Box) voltages
- Thread starter GiveUsYourBones!
- Start date
so here is what i've got. I checked the voltage coming into my pedal and it now registers 9.3V.
-the resistance readings to ground are all 183K. thats from all 4 points to ground.
-I checked the voltage to ground of the 10K resistor. the top point (closes to the transistor) Is 55.1mV and the bottom point is 9.35V.
I've added photos if that is helpful.
-the resistance readings to ground are all 183K. thats from all 4 points to ground.
-I checked the voltage to ground of the 10K resistor. the top point (closes to the transistor) Is 55.1mV and the bottom point is 9.35V.
I've added photos if that is helpful.
Attachments
Yes, the higher I go on the fretboard, the more compression happens. it allows the initial transient through but then squashes the notes volume considerably. it slowly regains volume as the note sustains. the lower octave notes on the guitar seem to not trigger this compression.
the knobs on the guitar were all 100% open. I have played around with the knobs on the pedal. 100% on the blend knob basically turns off the pedal. it needs to be rolled back to ~90% to have the most effect.
The build docs call for A50K pots in each location. I have verified that I have installed A50k pots.
Chas Grant
Well-known member
OK You have a lot of cold solder joints. Get your self a nice wet sponge that you can trash, then get a heavy duty paper towel or Kim-Wipe if you have access to them, if not a couple of regular paper towels will do. Fold the paper towels in half and roll them up somewhat tight. The roll needs to be about 1 inch thick,. When its rolled up use masking tape to keep it rolled, leaving rolled edges clear of the tape about an inch back. Flow solder onto you iron tip, then rub it on the sponge, then use the paper towel roll to completely clean the iron. Be fast with the towel roll so it doesn't burn. Your iron should be very clean and silver now. Do this every time be fore you solder a component. If doing multiple components, then do it every 3 or 4 components. A clean iron is a big part of a quality solder joint. Now your ready to reflow all the joints. Touch the iron tip to the solder to put a small drop of solder on the tip. Now touch the soldered joint and start counting in your head, not fast not slow just steady. By the time you get to 6 the solder should have reflowed. If it reflows before 6, keep the iron on the joint until 6. 6 seconds of heat will not damage the board. If you use the count to 6 rule on a new component, you should have a quality joint with proper flow through every time. If you really want quality joints then clean the board prior to soldering, a pink rubber eraser works wonders on the pads, followed by IPA, also clean the solder and component leads with IPA. When flowing solder on a new component, if your adding solder for more than 2 sec, then its too much. The Bigger the Blob, the Better the Job is a Fallacy! 
If you reflow the joints I hope there is a change in the circuit. Since your not shorted to ground, then the power is not getting to the collector of the transistor. The .05V on those points and also the base of Q2 will not allow this circuit to operate correctly so we have to figure out where your losing the voltage at.
If you reflow the joints I hope there is a change in the circuit. Since your not shorted to ground, then the power is not getting to the collector of the transistor. The .05V on those points and also the base of Q2 will not allow this circuit to operate correctly so we have to figure out where your losing the voltage at.
So...I reflowed those joints (im really new to soldering and cant spot a cold solder) and now it sounds AWESOME! I checked the voltage at every point and all seems right except for Pin 3 and Pin 13 on the CD4013 and the 47n cap. Since it is working properly and sounds great, should I be concerned and sort out the cause?
Thank you so much for taking the time to help me through this. I built a reverb pedal (the Spirit Box) after I assembled this and it works perfectly.
Thank you so much for taking the time to help me through this. I built a reverb pedal (the Spirit Box) after I assembled this and it works perfectly.
It kind of sounds like an analog synth. It has a bit of trouble tracking the note when I bend the string, but that is charming and gives it a bit of a glitchy sound. it actually sounds almost identical to the synth parts on Icky Thump by the White Stripes.
Chas Grant
Well-known member
The Spirit Box is a great Reverb!!! Built the circuit for my daughter and liked it so much I had to build me one!
Chas Grant
Well-known member
AWESOME!!!!
Pin 3 and 13 are perfectly fine. They are connected by a PCB trace and should be the same. 13 is the Q out put of the first flip flop and 3 is the clock input of the second, they will be 0 or 9 volts depending on state of flip flop. The 47n cap is also correct. It’s a decoupling cap removing the DC voltage from the signal before it goes through the volume pot and to the output Jack. The DC voltage may change depending on the blend pot and the signal into the circuit. Not to concerned about the dc voltage on the bottom of cap, but the 0V on the top is a must have. Without the 47n cap dc would go out of the circuit and make a nasty hum if fed straight into amp. And helping people troubleshoot is no problem, I enjoy it and I learn a lot also so it’s a win win!
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Chas Grant
Well-known member
The Spirit Box is based on the EQD Ghost Echo, so the ghostly feel is quite accurate!
Chas Grant
Well-known member
My amp has a spring reverb on it so I never thought I needed one, once I heard the spirit box I realized I really needed one!??? so of the 30 or so pedals I have right now only one is a reverb.
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