help a noob out? (slambox)

[jtn191]

So I'm building a Slambox as my very first build...

Now that I've got everything in the box, the LED doesn't light up when I give it power & plug into the stereo input



When I test it the bypass works fine...but engaged, there's a steady hissing that doesn't change in volume as the "slam" pot is turned

So here's a few questions on technique/materials before I give it another go tomorrow:
-for wire I bought this at Radioshack (yeah I know...) http://www.radioshack.com/product/index.jsp?productId=2049745 is that adequate?
-for jacks, I bought these http://www.smallbearelec.com/Detail.bok?no=793 because I liked how the ferrule looks, and then learned about how the TRS connections work from here http://www.freestompboxes.org/viewtopic.php?f=22&t=10457
-and for the switch...well it's pretty tight soldering in there. Any advice about technique for that?

Really appreciate it. Hope to have it running by tomorrow  

[maysink]

Did u put the LED in backwards? When looking top down, one side of the LED is flat--the flat side's leg goes in the pad closest to the "SW" pad on the PCB.

You can put the stomp switch's lock washer on the inside of the case to help keep it seated (stomp switch > metal lock washer > case > nylon washer > nut)

I can't tell if you're saying that it works with a hiss or just hisses when engaged...

[jtn191]

just hisses when engaged. no guitar signal.

I did a quick search and somebody had quite a similar problem with another pedal which leads me to believe: grounding problem?

[jkokura]

What's wrong with Radio shack? I've bought parts and wire from there lots!

I'm not sure of what the problem is because the images are quite dark and hard to see, but I can tell that your circuit is a big mess of wires. We need to have a better image if you'd like some help.

Usually, when the bypass signal is fine, it means your wiring isn't likely the problem, unless it's the wiring to and from the board (very possible).

What is often the problem in this case is either poor soldering, or a problem with a part. This is what you need to do:

Double check all the part values.
Double check all the part orientation (Especially the transistor - double check the pinout)
Double check the soldering job you've done, looking for solder bridges especially
Double check the wiring

Take a break.

Triple check it all again.

Fix anything as you come to it, and then start over (yes, start over). Sometimes the problem is something you're very sure isn't the problem. Don't take it for granted the wiring is fine, or the part values are fine until you've checked it many times. I've debugged pedals that I was sure I had all the right parts for, and it turned out the problem was I used a 100k resistor instead of the needed 100r resistor (VERY big difference).

hope that helps.

Jacob

[Jordo]

+1 for Jacobs advice.

Its painful but check everything....METHODICALLY!!

Sounds like a grounding issue.  Check solder flow.

Best of luck

[jiffy]

Get a multi meter and check firstly ground is ground, and +9V is also what it should be (on both the 3pdt switch and circuit board). Then continue to check over voltages etc..

The fact the LED isn't going means it might you might be lucky and just something missing or shorting.

[jtn191]

Thank you Jacob and Jiffy. I redid all the wires going from pcb to footswitch, which gave me the opportunity to make things neater and check everything. Now I think the problem is the wire going from DC jack to "9v" on the cb, as I don't think I've ever had a good connection. The pad is now missing for that particular area, which is a pain...

[jiffy]

What I often do when I screw up like that is attach directly to components, eg in your case solder the wire to the bottom of R3 or R5 or top of D1(side with the strip), they are all connected to 9V. Check the schematic/board layout to make sure you get the right side.

[jtn191]

^ roger, did it. Is it...possible to mess up a dc jack by melting the lugs internally, or something?

[jiffy]

Probably is possible although quite hard to. Do you have a multimeter to check the 9V is going to the board? To check the jack is okay you could put a probe into it, there should be a pin in the center. Then attach the  other probe to any ground eg ground on the in/output jacks. The DMM should have a continuity setting or otherwise measure the resistance should be 0 ohms. That will only check the -ve of the jack is working however it's hard to check the +ve as it's quite hard to get a probe into the jack.

[jtn191]

ah ok...yeah that was kind of a silly thought--I was checking the voltage of the lugs on the dc jack when plugged into a dc adaptor (just to see if I could get a reading since I'm pretty new to using multimeters too, and I wasn't getting anything.) But now I think I get it


The sound I just got when engaged is: a low lightsaber-like/ :02 to :04 of The Beatles "I feel fine" which grows then suddenly-->fairly quiet white noise/hiss


ps thanks for your patience. 1,000 Merry Christmases to ya

[jiffy]

Putting the multimeter across the 2 lugs on the DC jack do you get 9V?

[jtn191]

yes--when I touch ground and the lug that goes to "9v", I get 8v which is what my gfs ac adaptor puts out

[jiffy]

Okay that's good.
A few things to check:
1) you haven't got the power supply reversed? Put the black probe on the centre lug on the dc jack, and the red one on the lug to the side the multi meter should read 9V, not -9V, if it says -9V you have it the wrong way around. Also check at the CB red probe to 9V black to GND.

2) The LED, when the pedal is engaged there should be 9V on one side of R5 and on the other side 9V - 1.5V

3) Does pad 1 of the slam pot actually go to ground?

[jtn191]

1) tested, just to clarify: when I put

black probe-->lug that goes to cb   (middle lug on madbean's general wiring diagram)
red probe-->lug that goes directly to ground  (top lug on madbean's general wiring diagram)

I do get -9V. Does this mean the two red wires (on diagram) need to switch which lugs on the jack they're attached to?

3) I'm getting that pads 1 and 2 are going to ground