# Sandspur Fuzz no sound



## skymaster747 (Nov 18, 2021)

I build a Sandspur Fuzz everything looks find, and I test all the components before, installed.
When the pedal is bypass, the sound is normal, now when you engage the pedal there is no sound . Here are some pictures of the pedal in question thx


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## Big Monk (Nov 18, 2021)

Snap some pictures of the bottom of the board and post voltages for the transistors.


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## skymaster747 (Nov 18, 2021)

Let me check the voltage of the transistors but this is the expects on the package


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## skymaster747 (Nov 18, 2021)

6.6 M ohm


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## Big Monk (Nov 18, 2021)

skymaster747 said:


> 6.6 M ohm



What is this?


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## skymaster747 (Nov 18, 2021)

That is the Measure From the transistor legs. I look for voltate but was like 0.005 volta or something


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## skymaster747 (Nov 18, 2021)

Big Monk said:


> What is this?


Sorry found  it 25V


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## Big Monk (Nov 18, 2021)

skymaster747 said:


> Sorry found  it 25V



I meant for you to measure the emitter, base and collector voltages of the transistors with power connected.


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## skymaster747 (Nov 18, 2021)

Description​Installation style: Through Hole
Package / Box: TO-18
Transistor polarity: NPN
Configuration: Single
Collector-emitter maximum voltage VCEO: 25 V
Collector-base voltage VCBO: 30 V
Emitter-base voltage VEBO: 5 V
Collector-emitter saturation voltage: 0.25 V
Gain bandwidth product fT: 150 MHz
Minimum operating temperature:-65 C
Maximum operating temperature: + 200 C
Series: BC107
Package: Bulk
Collector continuous current: 200 mA
DC Collector/Base Gain hfe Min: 40 at 10 uA, 5 V
Pd-power dissipation: 600 mW
Product Type: BJTs-Bipolar Transistors
Subcategory: Transistors
Part number alias: BC108B PBFREE


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## skymaster747 (Nov 18, 2021)

Big Monk said:


> I meant for you to measure the emitter, base and collector voltages of the transistors with power connected.


Ah ok let me check. Thx for your help I’m still learning


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## Big Monk (Nov 18, 2021)

skymaster747 said:


> Ah ok let me check. Thx for your help I’m still learning



No sweat man. Take your time. I want to see if the transistors are getting suitable voltage and to make sure you didn’t burn them up soldering them in.


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## skymaster747 (Nov 18, 2021)

I’m looking for a video that show me how to check


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## Big Monk (Nov 18, 2021)

skymaster747 said:


> I’m looking for a video that show me how to check



Do you have a multimeter? 

Take the black test lead and touch it to the ground connection on one of your jacks. Take the red lead and touch it to the emitter, base and collector of the BC108s, respectively, and record the voltages. Also let us know the value of your power supply voltage.


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## BuddytheReow (Nov 18, 2021)

Set your meter to 20v dc while testing. If you're unsure of the pinout then just go left to right while viewing the board like in the build doc


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## skymaster747 (Nov 18, 2021)

Hope this help


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## skymaster747 (Nov 18, 2021)

Big Monk said:


> Do you have a multimeter?
> 
> Take the black test lead and touch it to the ground connection on one of your jacks. Take the red lead and touch it to the emitter, base and collector of the BC108s, respectively, and record the voltages. Also let us know the value of your power supply voltage.


I posted the pictures


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## Big Monk (Nov 18, 2021)

skymaster747 said:


> I posted the pictures



Im not really sure what’s what there. Just post them as text if you can.


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## skymaster747 (Nov 19, 2021)

Big Monk said:


> Im not really sure what’s what there. Just post them as text if you can.


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## skymaster747 (Nov 19, 2021)

At the collective and base using the negative lead of the multimeter show 3.5V when I combine the collective or base with the emitter they read 4.3V


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## BuddytheReow (Nov 19, 2021)

skymaster747 said:


> Hope this help


This doesn't tell us much since we can't really see what it is you're testing. Have the black lead to ground (either on the black circled pad or wire coming from it below) and the red probe to each of the leads of the two transistors going from left to right. I am also including a pinout of the bc108 for your future reference. From left to right on the board it is emitter, base, collector. Write down each of the voltage readings and post them back here in text format since pics of your multimeter make it more confusing for us.


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## skymaster747 (Nov 18, 2021)

I build a Sandspur Fuzz everything looks find, and I test all the components before, installed.
When the pedal is bypass, the sound is normal, now when you engage the pedal there is no sound . Here are some pictures of the pedal in question thx


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## skymaster747 (Nov 19, 2021)

Ok I set the multimeter in V auto. Apply power to the circuit use the black lead to the PCB Ground and with the red Lead I touch the bottom of each leg


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> Ok I set the multimeter in V auto. Apply power to the circuit use the black lead to the PCB Ground and with the red Lead I touch the bottom of each leg



Ok. Now we are getting somewhere!








Take voltage readings at these points and report those.

Your transistors are not showing the expected voltages for this circuit. Did you keep heat on them for a long time?


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## skymaster747 (Nov 19, 2021)

No I didn’t heat them up I was quick. Those measure 1k and 33k. I got 2 extras that are new just in case


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> No I didn’t heat them up I was quick. Those measure 1k and 33k. I got 2 extras that are new just in case



I meant to measure voltage at those points. I want to see what voltage is making it to the collector resistors. Also, measure voltage coming in from the power supply:


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> Ok. I think now I did it right look this is the results I got



I would expect the collector voltages for Q1 to be around 1.3 v and Q2 at around 6 v.

Is the LED powering up? Do the voltages on Q2 change if you change the internal bias and Sundial control?


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## skymaster747 (Nov 19, 2021)

Ok this is correct .


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## Coda (Nov 19, 2021)

Have you adjusted the trimmers at all?


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## skymaster747 (Nov 19, 2021)

Q1 are E=0 / B=0.241V / C=0.843V
Q2 Are E=0.244V / B=0.843V / C= 0.274V
The 33K=8.43V
The 1K =0.0V
The power input = 9.51V


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## skymaster747 (Nov 19, 2021)

Coda said:


> Have you adjusted the trimmers at all?


Ten trimm pots ? They are in the middle


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## Coda (Nov 19, 2021)

Turn the bottom one all the way to the right and then measure the voltage of the collector of Q3 (black probe goes to ground).


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> Ok this is correct .



Does your LED light up? 

As @Coda said, try turning the trimmer up and see if it changes the Q2 voltage.


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## skymaster747 (Nov 19, 2021)

Yeah my LED function normally


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> Yeah my LED function normally



If you turn the Sun Dial knob and the internal trimmer knob all the way to the right, what is the collector voltage on Q2?


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## skymaster747 (Nov 19, 2021)

I see that the emitter in Q1 reads Zero


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## skymaster747 (Nov 19, 2021)

The colector In the Q2 is 0.274V


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> The colector In the Q2 is 0.274V



What about when you turn the bias knobs all the way to the right?


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## skymaster747 (Nov 19, 2021)

The same


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> The same



Try reflowing all the joints from the power rail to the transistor. If that does not get normal voltage to the collector of Q2, then it’s shot.


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## Mcknib (Nov 19, 2021)

Are you using a battery snap it's difficult to see but looks like you've got 3 wires to your DC jack where are they wired to

What voltage do you get to the pcb


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## skymaster747 (Nov 19, 2021)

Yeah I have a batterie snap . 
The voltage into the PCB is 9.51V


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## skymaster747 (Nov 18, 2021)

I build a Sandspur Fuzz everything looks find, and I test all the components before, installed.
When the pedal is bypass, the sound is normal, now when you engage the pedal there is no sound . Here are some pictures of the pedal in question thx


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## skymaster747 (Nov 19, 2021)

I just buy some TRANSISTOR SOCKET . I will install those and try different transistors


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## Coda (Nov 19, 2021)

skymaster747 said:


> Yeah I have a batterie snap .
> The voltage into the PCB is 9.51V


Where does the middle lug of the 9v jack connect to?


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## skymaster747 (Nov 19, 2021)

One is going to the Board the other to the 9v and the other to ground


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## Coda (Nov 19, 2021)

skymaster747 said:


> One is going to the Board the other to the 9v and the other to ground


Right, I mis-read.


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> Yeah I have a batterie snap .
> The voltage into the PCB is 9.51V



Do you have continuity from power down to the collector?


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## skymaster747 (Nov 19, 2021)

Yes


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## Big Monk (Nov 19, 2021)

skymaster747 said:


> Yes



Q2 is probably shot then.


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