# Mantle Fuzz (MXR Blue Box) voltages



## GiveUsYourBones! (Nov 25, 2019)

In case anyone needs them, here are the voltages from a working mantle fuzz pcb.


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## Nostradoomus (Nov 25, 2019)

Nice one! Mine worked out the gate but this is a slick idea


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## GiveUsYourBones! (Nov 25, 2019)

Thanks, yeah mine worked great until I fudged the octave mod and shorted pins 1 and 3 on the CD4013.... Luckily I was building 2 at the time so I took the voltages from the working one.


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## Tanner30 (Nov 22, 2020)

Hi guys, The Mantle Fuzz was my second pedal build and I'm having a couple issues and need some guidance. It is woking but it doesn't seem to be loud enough, and the actual effect seems odd (wish I could describe it better). Anyway, i've checked all the components to ensure they're the correct values and have checked for any simple mistakes (wiring incorrectly, solder bridges, etc...) and everything seems fine. 

1. I checked all components and my 56K resistors are mostly registering around 32K on my multimeter. is that an issue? 

2. I have checked the voltages and have my calculated numbers in the photo. the majority seem to be spot on, or very close. several seem to be way off from the ones GiveUsYourBones has listed. I am not sure why they are so far off and how to correct the issue?  

Thank you in advance!


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## Chas Grant (Nov 23, 2020)

Tanner30 said:


> Hi guys, The Mantle Fuzz was my second pedal build and I'm having a couple issues and need some guidance. It is woking but it doesn't seem to be loud enough, and the actual effect seems odd (wish I could describe it better). Anyway, i've checked all the components to ensure they're the correct values and have checked for any simple mistakes (wiring incorrectly, solder bridges, etc...) and everything seems fine.
> 
> 1. I checked all components and my 56K resistors are mostly registering around 32K on my multimeter. is that an issue?
> 
> ...


Which 56K resistors are you referencing as 32K. There are a lot of 56K resistors in this circuit.  If taking resistance measurements in a circuit, there may be parallel paths that are not readily apparent, this will cause the resistors to read lower than their marked value. So the readings you are getting may be normal. You have to look at the schematic to see if you have a parallel path and take that into account.


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## Tanner30 (Nov 23, 2020)

Thanks. I am not experienced enough to reliably follow a schematic to check for parallel paths, but I will give it a shot. I have used a red dot to indicate the resistors that are registering around 32k on this screenshot. That would make sense the reason why some are registering a different value. I checked each component with my multi before installing on the board and everything registered correctly. 

Any thoughts on the differing voltage readings? specifically the pins on CD4013 seem to be vastly different.


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## BuddytheReow (Nov 23, 2020)

If you tested all components before soldering and still notice resistance after, regardless of the value, you should be alright. Did you check caps too?


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## Tanner30 (Nov 23, 2020)

I did check the caps. everything checked out okay. audio passes and the effect is obvious when played. it is just quiet and higher octaves are incredibly unstable. that prompted me to explore a bit further.


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## Tanner30 (Nov 23, 2020)

the other thing that is odd, the harder you play (strum or pick) the quieter it is. if I pick a note very lightly, it seems to react normally. If I pick hard it acts like a compressor forcing down the volume dramatically. Any ideas why?


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## Chas Grant (Nov 23, 2020)

Tanner30 said:


> Thanks. I am not experienced enough to reliably follow a schematic to check for parallel paths, but I will give it a shot. I have used a red dot to indicate the resistors that are registering around 32k on this screenshot. That would make sense the reason why some are registering a different value. I checked each component with my multi before installing on the board and everything registered correctly.
> 
> Any thoughts on the differing voltage readings? specifically the pins on CD4013 seem to be vastly different.


The CD4013 is a Flip Flop, the voltages on this will seem weird until you look at them and the schematic and the pin out of the chip. Pins 4, 6, 8, and 10 are grounded and should be 0V, which they are. 12 is connected to 9, they should be the same, they are. 2 is connected to 5, they should be the same, they are. 13 is connected to 3, they should be the same, they are. Pin 14 is Vcc, good and pin 7 is ground also good. The Flip Flop will change states when CL2 (Pin 11) goes from low to high, this will depend on the signal from the guitar. The strange voltage I see is on the transistor on the top right. You have .05, it should be higher. Look at the other transistors.

As for the 56K resistors, I don't see the circuit designations any where, just the component values. But you have 8 of them with red dots, and looking at the circuit there are 8 that have parallel paths.


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## Chas Grant (Nov 23, 2020)

OK, the transistor in question looks like Q1. The 0.05 should be reading the same as pin 11 of the CD4013, its not. Check resistance between the pin 3 of the transistor and pin 11 of the CD4013


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## Tanner30 (Nov 23, 2020)

just checked and im registering 0 resistance between pin 11 on CD4013 and pin 3 on the transistor.


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## Dan0h (Nov 23, 2020)

GiveUsYourBones! said:


> In case anyone needs them, here are the voltages from a working mantle fuzz pcb.


This is such a great idea having an image of the PCB with all the V values. Would save a ton of time trouble shooting and forum diving, but would also take a lot of work to put together.


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## Chas Grant (Nov 23, 2020)

Tanner30 said:


> just checked and im registering 0 resistance between pin 11 on CD4013 and pin 3 on the transistor.


OK check resistance between these points, should be close to 0 ohms. Electrically they are the same point so they should have same voltage. When the transistor conducts, the voltage goes low but should be greater than .6V, when the transistor is not conducting it will go high up to +9V.


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## Tanner30 (Nov 23, 2020)

I'm reading 0 at all these points. I tried Pin 11 to the 1M resistor and the 10K. I also tried the 1M to the 10K then the transistor to each resistor. all read 0.


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## Chas Grant (Nov 23, 2020)

And you are sure that you have 4.5 on pin 11 and .05 on the 3 other points (scratching my head)


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## Tanner30 (Nov 23, 2020)

Okay, so two things. 1. I have no idea why it is different now (I'm sure I did something wrong just not sure what), but i'm reading 44.4mV (0.04V) on all the points listed above. 2. my power supply is now supplying 7.9V instead of 9.3V as I recorded earlier. I checked the voltage on all points, and a couple of the values are now quite different (as seen in blue on this graph). most are the same or within a reasonable margin. 

I truly appreciate your help with this.


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## Tanner30 (Nov 23, 2020)

forgot to attach the file.


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## Chas Grant (Nov 23, 2020)

Now we might be getting somewhere, those values make more sense. Either you have a short to ground or the 10K resister is opened, my guess is on the short to ground.  Take a resistance reading from the same points to ground, the first one will tell you if you have a ground. The resistance should be fairly high if good. If its low, first carefully remove the CA4013 and recheck. If resistance is still low after removing CA4013, try replacing the transistor, that's the most likely culprit. If resistance is high after removing CA4013, then replace the IC. 

If on your initial check,  resistance to ground is high then measure 10K resistor below the transistor on the right. An open resistor would give you the same voltage readings.

And its no problem helping you out. I learn a thing or 2 doing this and that's always good.


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## Barry (Nov 23, 2020)

Maybe some pictures of the actual build would help


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## GiveUsYourBones! (Nov 25, 2019)

In case anyone needs them, here are the voltages from a working mantle fuzz pcb.


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## nichgriff (Nov 24, 2020)

Tanner30 said:


> I did check the caps. everything checked out okay. audio passes and the effect is obvious when played. it is just quiet and higher octaves are incredibly unstable. that prompted me to explore a bit further.


What do you mean by higher octaves? Do you mean playing higher on the fret board? Curious on where your knobs are set as well. Did you make sure you used the right potentiometer too?


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## Tanner30 (Nov 24, 2020)

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.


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## Tanner30 (Nov 24, 2020)

nichgriff said:


> What do you mean by higher octaves? Do you mean playing higher on the fret board? Curious on where your knobs are set as well. Did you make sure you used the right potentiometer too?


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.


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## Chas Grant (Nov 24, 2020)

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.


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## Tanner30 (Nov 24, 2020)

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.


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## Tanner30 (Nov 24, 2020)

again, I missed adding the file.


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## nichgriff (Nov 24, 2020)

Tanner30 said:


> 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.



awesome! Great to hear. 

how’s the spirit box? I was considering doing one soon.


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## Tanner30 (Nov 24, 2020)

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.


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## nichgriff (Nov 24, 2020)

Tanner30 said:


> 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.


The spirit box? Or are you talking about the mantle fuzz? I’m assuming you mean the mantle fuzz because that’s what mine sounds like too haha


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## Chas Grant (Nov 24, 2020)

nichgriff said:


> awesome! Great to hear.
> 
> how’s the spirit box? I was considering doing one soon.



The Spirit Box is a great Reverb!!! Built the circuit for my daughter and liked it so much I had to build me one!


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## nichgriff (Nov 24, 2020)

Chas Grant said:


> The Spirit Box is a great Reverb!!! Built the circuit for my daughter and liked it so much I had to build me one!


My issue is of the 6 pedals I have - 3 are reverbs! Haha haven’t built one yet because of that but it’s my favorite and most used effect.


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## Chas Grant (Nov 24, 2020)

Tanner30 said:


> again, I missed adding the file.



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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## Tanner30 (Nov 24, 2020)

sorry, yes, the Mantle Fuzz. The Spirit Box is interesting. the echos are very closely spaced and trail off at certain settings. it actually has a bit of a ghostly feel. it's quite different from any other pedal I own.


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## Chas Grant (Nov 24, 2020)

The Spirit Box is based on the EQD Ghost Echo, so the ghostly feel is quite accurate!


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## Chas Grant (Nov 24, 2020)

nichgriff said:


> My issue is of the 6 pedals I have - 3 are reverbs! Haha haven’t built one yet because of that but it’s my favorite and most used effect.



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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## nichgriff (Nov 24, 2020)

Chas Grant said:


> 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.


Ha! My amp has reverb too which is always on. OBSESSED. 

I was considering building a dual build with the ghost echos and space spiral (whatever they're called on here) - I think it would be a crazy ambient machine!


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## Tanner30 (Nov 24, 2020)

Here are photos of the Mantle (T-800) and Spirit Box (Spectre). I have a few reverbs and love them all for different reasons.


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## Chas Grant (Nov 25, 2020)

They turned out nice!


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