Colortone Bass Fuzz v3

[Anonymous]

Hello,

I have a problem with a Bass Fuzz pcb. I made one last year and it works very well (pcb v2). I ordered one this month and I received a pcb v3, but the documentation is for the v2. I build the v3 like the v2, but it doesn’t work. When I engage the pedal, the sound it’s just like a boost and zero fuzz. I see there is one more resistor in the v3 (R24), I jump it in my build as you can see in the picture.

Thank you so much for your help

Thibault

[Barry]

Hi,

The only thing we did was add a resistor to the final stage. It will not cause you a problem but you do need to put a 33k resistor in there. You could also use 20k, 22k or 27k as well if you need to. After doing that you will need to adjust your trimmer T2 to bring the Boost Level up so it is not attenuating the circuit which maybe be the case now?

If you try turning up T2 first you will have to turn it back down after installing R24. That is the reason for the new resistor to keep you from attenuating the whole circuit.

The only other thing is technically you should use a 1N5817 for D4 but it will work with a 1N4001 as well.

If you still have issue after placing the resistor in R24 there is some other issue that needs to be investigated.

 

[Anonymous]

Hi Barry, thanks so much dfor your help !

I see a difference for T1, 20k instead of 5k in v2. It’s significant ?

[Barry]

It is only significant if you cannot bias your JFET.

Test the Drain of Q4. Make sure you can adjust T1 so that the Drain voltage of Q4 reads between 4.5v to 6.5v

If you can get a satisfactory voltage reading then everything is fine.

Also if you are using 2N5088 transistors Q1 – Q3 they do align with the board silkscreen now but if you are using BC549C then you would have to install them opposite the board silkscreen.

[Anonymous]

Hello Barry,

Thanks for your help. I added R24, changed D4 for 1N5817, biased the JFET correctly with no problem, but nothing helped.
I tried flipping all 4 transistors and nothing either. I changed them all with new ones and placed them the right way around and the sound remains as before (the pedal sounds like an obscure boost, zero fuzz). I checked all the values of the components before soldering them, I checked all the solders and they are ok. I have no other idea, I see nothing else.

Are you sure the v3 board is ok? Have you assembled it yet?

[Barry]

Yes it has been assembled. There could be a manufacturing error but that is rare, though possible.

There is too much missing information we absolutely need to do a proper troubleshoot.

Lets start with this:

• Set  T2 at the center position of the rotation
• What transistors are you using?
• What are the voltage readings for all 4 transistors?

List them in order:

Q1 thru Q3

E:

B:

C:

etc…

Q4 is:

D:

S:

G:

 

  

 

The information will be very revealing and may lead to a solution. If not I will need more important information.

[Anonymous]

Hi Barry,

Thanks so much for your help. I use 3x 2N5088 for Q1 through Q3 and 1x J113 for Q4. I tried with the transistors of my bass fuzz v2 (which works very well) and the problem is the same.

The voltage for the 4 transistors :

 

Q1

E: 0.03V

B: 0.61V

C: 3.89V

 

Q2

E: 0.04V

B: 0.63V

C: 4.63V

 

Q3

E: 0.03V

B: 0.62V

C: 3.41V

 

Q4

D: 5.27V

S: 1.20 V

G: 0V

[Barry]

OK thank you.

Tell me the value of these two red Wima capacitors.

Top value =

Bottom value =

 

Verify proper orientation of FUZZ pot. Lug 1 pot to Lug 1 board silkscreen.

Since you are using 2N5088 install in the same orientation as the board silkscreen.

[Anonymous]

It’s okay for the FUZZ pot.

Top value = 1nF

Bottom value = 220nF

[Barry]

I will be working on a resistor chart for comparison tonight and tomorrow.

In the meantime please verify all the capacitors one by one since I cannot see them.

If all the capacitors are in order per the new schematic compared to the board then I need you to do some basic troubleshooting steps that I do every time I have a problem with a build. And yes I have to troubleshoot builds even though I have built a couple thousand circuits.

Here are the basic mandatory troubleshoot steps:

• Pull the board out from the enclosure and lightly pull on all off board wiring making sure it is connected well
• Triple check all off board wiring connections to 3PDT and IN/Out Jacks.
• check the physical connection and interaction while inserting a cable in each jack. Look for proper contact
• re-flow the solder for ever single component whether it looks great or not (have solder handy)
• check solder joints on all off-board items like 3PDT and In/Out Jacks. (re-flow if needed)

Report back after you have verified all capacitors and did all troubleshooting tips above.

If you have an Audio Probe this would also be very revealing to quickly show the problem area of the board

Thanks.

 

[Anonymous]

Hello Barry,

Thanks for your help. Do you have a picture of the new pcb with the component number? As the capacitors are already in place, I can’t know the number of the components hidden below, it will save me from desoldering everything.

I don’t have an audioprobe, I think I’m going to make one the next time I place an order.

[Barry]

Yes I should have led with that.

Here you go.

[Anonymous]

All you really need for an audio probe is an old guitar cable you’re willing to sacrifice and a capacitor, something in the 100n – 220n range should be fine. That will prevent DC voltage from passing and damaging your amp. Guitar signals are AC, aka sine waves, wave up, wave down, wave up wave down.

You would just cut one end off a guitar cable, peel back the outside sheathing a few inches to reveal the tubular braid, unwind that some and put some heat shrink over it, and connect a wire to it which goes to ground on your pedal’s power source. Then connect one end of the capacitor to the middle wire, and on the other end of the middle wire, attach a piece of wire so you can reach your circuit board. On the other end of that wire, solder a paperclip or an alligator clip or whatever you want to poke and prod the circuit with. Plug the cable into an amp, and feed signal into the in jack of your build.

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