Stuffing an Enclosure and Grounding

Seven64 · May 13, 2011, 12:23:36 PM

Well, I finished another PCB, but just received my first enclosure in the mail. I have built another pcb and got it working without an enclosure, but now I cannot get my new build to work. It is a vero layout of the Little Angel Chorus, and I am pretty sure the problem is in the off board wiring.

I used the smallbear 3pdt pcb, and I think that is giving me more problems than helping me. I have a 9v wall source, a 9v battery clip, LED, mono jack, and stereo jack.

Mono jack-
Tip - to #8 on smallbear PCB
Ring/Sleeve - to sleeve on stereo jack

Stereo jack -
Tip - To #4 on smallbear PCB
Ring - to neg 9v battery and little angel ground spot on 9v plug
Sleeve - to ground on smallbear pcb and ring/sleeve on mono jack

9v wall source -
GND - ground to PCB, ring on stereo jack, and neg 9v battery clip
POS - pos on PCB
POS2 - pos on 9v battery clip and + side of LED

I think this problem is in this wiring, does anyone care to help me out?

Seven64 · May 13, 2011, 12:27:58 PM

oh, and when i was testing it i could play clean through it, but when i hit the stomp switch i got a little feedback, but the LED didn't turn on and there was no effect.

Govmnt_Lacky · May 13, 2011, 12:41:08 PM

If you are using a DC jack AND a 9V battery clip then you need to wire the grounds (V-) like this:

1) The black lead from the battery clip (V- or GND) will ONLY connect to the Ring of the Input jack. There should be no other connection on the input jack ring.

2) The V-/GND connection form the DC jack will connect to the other V-/GNDs in the circuit. This includes the Input jack Sleeve, Output jack sleeve, Circuit ground, etc.

Being wired like this, when you insert your instrument cable into the Input, the INPUT jack's ring and sleeve are shorted and enables current flow through the battery.

Good Luck

Seven64 · May 13, 2011, 01:17:42 PM

got it, and got it working outside of the enclosure, but when i put it in the enclosure it doesnt get any signal to them amp at all

R.G. · May 13, 2011, 01:24:27 PM

Classical problem, hashed here many times.

When you mount it in the enclosure, the enclosure is connecting two or more places which are not grounded outside the enclosure.

There is no simple way. You have to find the points which are being shorted. It is specific to your setup, your wiring, your controls and your board.

Seven64 · May 13, 2011, 01:29:13 PM

could it be pots to jacks?

also, now there is LOTS of feedback when the effect is bypassed

R.G. · May 13, 2011, 01:43:20 PM

Sorry not to be more helpful; yes, it could be pots and jacks. It could be *anything* which now touches that didn't when it was outside the enclosure.

Sudden screaming oscillation is usually caused by wires connecting to sensitive points now being shoved close together so that the capacitance between them allows feedback to happen. The exact placement of wires is called "wire dress" in the electronics wiring trade.

vendettav · May 13, 2011, 01:50:27 PM

I think it could be this: if you're using a metal jack for your 9v input and using the center negative polarity then it'll simply gruond the 9v. that's why the LED won't light up

just my two cents

Govmnt_Lacky · May 13, 2011, 02:41:17 PM

This wouldn't happen to be a Positive Ground circuit would it?

Link to schematic/project file?

Seven64 · May 13, 2011, 06:20:30 PM

got the LED to work, i hooked up the + end wrong.

also, i put some electrical tape on the inside where i mount the pots, and got it to work! also covered the bottom of the PCB with electrical tape.

now i just need to get rid of this feedback...

http://www.sabrodesign.com/wp-content/uploads/2011/04/LittleAngelRev1.gif

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Stuffing an Enclosure and Grounding