Messages

Here is the Mangler I built.
Thanks to aestoval for tipping me off to the pre gain mod.

Cool looking pedal. I just built a mangler and think the pre-gain would be a great addition. How was that accomplished? Thanks!

Well if you have an external bias knob you will not need to use the resistors. The resistors are to properly bias the transistor to 4.5v I believe.

Thanks. That's my take as well. I'm installing the exterior bias partly for looks and partly as an experiment. This is my first Fuzz Face build so I'm still learning.

Hi, I'm getting ready to build a MB "Mangler" and will be using an external bias knob instead of the trim pot. I'm using a matched set of PNP trans from Small Bear. These come with recommended resistors to achieve the correct bias. My question is: If I'm able to bias on the fly with the bias knob should I use their recommended values or is that not necessary given that the bias can be adjusted. Thanks in advance!

You've got a 470K in R3 instead of a 470R.  That'll do it every time.

Hey, mgwhit made my day friend Replaced the R3 and the Fatpants is singing!!

Wow, what a beautiful enhancement for a Strat. I've got one with Lollar Tweeds and another with Copperheads and both sound really good. Damned if the Fatpants didn't make 'em sound better. I'm a happy pedal builder.
Thanks to everyone for their help!

Great example of a team effort and an efficient debug. Great job everyone!

Jacob

This forum blows me away. Really great vibe and fast feedback. Really makes me feel confident about moving forward with this little obsession of mine 

Thanks everyone. Off to radio shack! Really looking forward to hearing this pedal. I'll post a build report soon.

[.022uf ECQ]

Just to be sure, here is what I ordered and installed for the film caps.

C2/C3   22n = .022uf ECQ
C4        100n = .1uf ECQ

Are these correct?

You've got a 470K in R3 instead of a 470R.  That'll do it every time.

Yep, You're right. Beginner mistake  I ordered the wrong resister. One more thing to buy at RS.

Great feedback, thanks!

The center lug is connected to ground though right?

Yes. Man, I thought I was being careful to show all the wires clearly. Obviously I needed another coffee

The ground wires all run to the output jack. One wire to the center lug of the switch.  All of my ground wires and the output wire are black.

Thanks Kaleb

Kaleb, just looked at the photo again and I can see how it might look like the ground is connected to the input.
that ground wire is actually floating above the input. Just a trick of the camera perspective. thanks.

Hi, sgmezie. Thanks for the suggestions. I can get a sub at Radio Shack to try.

Hey Waterman, the cap is marked with a shiny enamel on the top like that. It came that way and I've seen others like it before.

Kaleb, I've not mounted the PCB yet so it's not touching at all. I'll use foam tape when I get it to work. I've double checked the switch and associated wiring and all appear to be fine. Here's a link to the wiring scheme http://gaussmarkov.net/wordpress/thoughts/wiring-up-a-1590b/

Thanks for the feedback guys.

[gaussmarkov]

Hi, just built a Fatpants. First, let me say this was my first Madbeans board and it was a pleasure to work with. Logical layout and GREAT Documentation! I'll be using more of them in the future.

Back to the issue. Here's what I'm getting:

Clean bypass signal
LED lights up
With pedal engaged with Volume maxed a little less than unity
NO change when adjusting the Bias Knob 

What I've checked:

  All Grounds confirmed
Continuity on all other parts of the circuit
Getting 17v at the extra pad as well as the trim pot
All resistors confirmed before install and after
Diodes confirmed- ok
All capacitors are 25v or higher
I used the gaussmarkov wiring and it's confirmed (I like it for it's simplicity. Leads will be trimmed when I have a working build.)
Parts values confirmed (Multiple times)
Traces intact and no solder bridges- overall fairly clean
Both Pots confirmed for range and value

So, don't know where to go next. I suspect the J201. Are these sometimes defective?
I don't know how to verify the film cap values other than from my order.

Any thoughts or ideas appreciated. Thanks!

Thanks Jkokura. That's exactly the info I need. 

Hey, thanks for the really fast response. This is a great forum!

Let me take this a little further into a generic application. In general, when using a linear pot
to adjust bias what is the difference between using a 10k, 25k or 50k? Do higher values provide
a greater range or expand the accuracy of the biasing? Thanks!

Hi, I want to use an external bias knob for the Mangler. What kind of pot and rating should I use? Linear, Audio, Reverse? Thanks!