Slambox build, help!

[MullisMan]

Hi all,

I'm building a slambox, and I've got it all wired up, and I know I should have tested this on a breadboard before I got it all in an enclosure, but I figured since it was such a simple circuit I'd be fine.  I'm not a complete newbie, but when I engage this pedal, I get nothing.  I've checked all my solder points, everything looks good, switch wiring looks fine, and so does the jack wiring.  I double checked the BS170 pinout to make sure I had installed it in the sockets correctly, and everything looks good.

Signal comes through fine when the effect is bypassed but when I switch it on, it's gone.  I took a voltage reading on the transistor to see what I was getting, and this made me a little curious:

At the gate, i'm getting .8 volts, and then at the drain and source, basically nothing.  The meter won't settle on a value.  This is with the pot wide open.  Another question, I'm using the alpha 9mm pots, are the terminals on these the same as the 16 mm?  When looking at the back of the pot, from left to right it would be 3,2,1 correct?

I'm at a loss here....

[gtr2]

Did you double check your DC jack wiring?

http://www.smallbearelec.com/Detail.bok?no=93

[irmcdermott]

Did you double check your DC jack wiring?

http://www.smallbearelec.com/Detail.bok?no=93

I was just getting ready to say that. Sounds like you aren't getting power to the board. Double check your wiring also.

Did you socket your transistor? If you didn't it might be fried.

[jkokura]

If you're not getting power to the Mosfet, you've got a problem between the power jack, and the transistor. Follow that back to the source.

Try this - plug your power in and use your mulitmeter to measure power in a few places:

At the jack

At the board

After each component between the power in to the board and the drain of the mosfet. If you take a look at the build documents you can clearly see that the power goes through R3 and then heads by C2, then by R2 and then into the drain. If ANY of those components are faulty, or the solder job isn't good, then your power isn't getting to where it needs to be. One trick is to double check the value of R3 - if it's the wrong value that might just be the problem right there! Another common problem is to have power at the jack, but no power at the board, indicating that your wire is no good.

Try and see! Should be an easy fix!

Jacob

[MullisMan]

Hey guys, definitely was a simple fix once I realized what was wrong.  I realized that I forgot to add a trace between R3 and C2!    Used a cut resistor lead on the bottom of the board and voila! Works like a charm now.  Really digging this build.  Thanks for all the suggestions and help!

[irmcdermott]

Awesome! Glad you got it working! Post some picks once it's all finished!

[MullisMan]

Hey guys, here are some pics of the finished build.  It's pretty messy inside but this is my first 1590A build, so bear with me.  I'm just glad it was an easy fix, I was so frustrated thinking I had wasted a board.  Thanks for all the help again.

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