Fatpants No sing.... Help

[Bluestrat]

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!

[sgmezei]

I would try swapping the J201 since you have it socketed. If you dont have another you can use this handy sheet.
http://www.aronnelson.com/gallery/main.php/v/DRAGONFLY-LAYOUTS_0/The-Mod-Zone-_/TRANSISTOR_SUBSTITUTION_CHART.gif.html

Also, I would check the switch. I have fried one of those before. Also you could try swapping the IC if you have another.

I am sure others will chime in with some advice.

[401waterman]

What's that black mark atop the far left capacitor near the transistor? Did you burn it?

[k.rock!]

Are you isolating your PCB bottom from the pot enclosures?

I'm a bit suspicious about the way your inputs are connected at the switch....it seems to me like you have the tip going to the board AND to ground...I might be wrong, but check for continuity when the pedal is on, and see if your input is grounding somehow...although that would end up in no sound at all...but, just in case


-Kaleb

[Bluestrat]

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.

[Bluestrat]

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.

[k.rock!]

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.

Oh I see...well, FWIW, I was talking about the small jumper that ties the top left corner of your switch to the bottom middle lug. The center lug is connected to ground though right?

-Kaleb

[mgwhit]

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

[Bluestrat]

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

[Bluestrat]

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!

[Bluestrat]

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?

[k.rock!]

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?

Yes, that's correct.

Good eye mgwhit! Seems like that will take care of your problem man


-Kaleb

[Bluestrat]

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

[jkokura]

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

Jacob

[Bluestrat]

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