Holy MOLY Power Confusion!!

fifteenrabbits · January 19, 2012, 09:00:37 PM

alright! I've been trying to diagnose this for I'd say two hours. It's dumbfounded me.

It's so simple! The circuit that I'm building is an amalgam of the following three.

This:

http://www.beavisaudio.com/techpages/PedalHacker/LooperWithFeedbackLoop.gif

with an added battery bit (all the way at the bottom):

http://www.beavisaudio.com/techpages/PedalPower/

and adding a fine tune knob (schematic 3):

http://pianointune.blogspot.com/2011/04/voltage-division-with-coarse-and-fine.html

So, I'm just wiring up my led. This is where I've run into problems.

Everything is passive but the LED. It's very simple.

Here are my symptoms:

LED operates as it should with just a battery. It:

turns on when I plug in the output. (that's how I want it)
turns on and off with the bypass switch.

HOWEVER:

When I plug in the wall-wart, all voltage disappears!

...It gets spookier!!

When I UNPLUG the output, which was bridging the ring and sleeve connectors to complete ground, my voltage is un-shorted!!

You see, so with the battery, it only works when I plug in the output to connect ground, but when I have the wall-wart in, the output-ground-completion somehow SHORTS the 9V to NOTHING!

so, if I bypass the ring-sleeve ground thing, and just hook up a test lead to the ring where my power's ground is, I get voltage as long as the plug isn't in!! Blows my mind every time!

Is this a symptom of some sort of protection circuit or misbehavior of the wall-wart?! I have no other wall-warts handy to test!!

Please help! I need this done tonight!

CurtisWCole · January 19, 2012, 10:04:28 PM

What kind of dc jack are you using? Is it plastic or metal?

Curtis

fifteenrabbits · January 19, 2012, 10:25:45 PM

It's metal. no continuity between any of the terminals and the body, I quadruple checked.

CurtisWCole · January 19, 2012, 10:36:00 PM

Does it work outside of the enclosure? Do you have a spare jack to replace the output jack? Is it possible that the dc jack wiring is off. If it's of the switching variety, that could cause the whole thing to crash. Sorry for not being better at this...I'm trying.

Curtis

fifteenrabbits · January 19, 2012, 11:07:11 PM

Oh boy. Looks like I'm not finishing this pedal as soon as I had hoped.

I have to get to bed so that I can go to work first thing in the morning.

but, yeah... I haven't taken the circuit out of the enclosure. I got the LED(s) working entirely without the jack. Still same problem with the jack. then I wired up the effect and there was a bunch of nonsense. It definitely did some feedbacking, but there was also a lot of noise and the original signal missing. There's something awry in that box!!

I'll take it out of the enclosure tomorrow after work. If anybody else has any other ideas, I'm all ears!!

thedefog · January 19, 2012, 11:13:14 PM

You definitely need to do some continuity tracing in your ground network. Something is touching somewhere that shouldn't be. Just trace your positive rail and see where it is going from the power jack (while unpowered). Got any pictures?

fifteenrabbits · January 19, 2012, 11:16:29 PM

pictures!

the ground network was totally revamped halfway through.

I was taking these pictures for the person who's going to own the pedal when it's done.

http://photobucket.com/evanslooper

tubegeek · January 20, 2012, 12:46:01 PM

Your workbench is almost as bad as mine!

markeebee · January 20, 2012, 01:05:10 PM

Blimey, could you take a few more photos next time?

Quote from: fifteenrabbits on January 19, 2012, 10:25:45 PM
It's metal. no continuity between any of the terminals and the body, I quadruple checked.

Are you sure? Sometimes quad isn't ruple enough. Those sort of jacks usually have continuity between the jack body and plug sleeve which would explain how you're getting DC on your ground (via the enclosure and pot & switch bodies). Try taking just the DC jack out of the box and see if it behaves any differently.

kimelopidaer · January 20, 2012, 04:03:12 PM

What about the pins on the DC jack for wall power?
I found out myself just yesterday that even though there are two positive pins on the back of it,
If the positive lead to the battery is wired to the wrong pin,
The power will be cut when the jack is plugged in.

k

CurtisWCole · January 20, 2012, 04:18:42 PM

That's what I thought as well.

Curtis

tiges_ tendres · January 20, 2012, 06:37:59 PM

It's your power jack.

Those are the funny ones that are intended for center positive use, right?

fifteenrabbits · January 21, 2012, 11:23:59 AM

It's my goddamn power jack!

Yes, ladies and gentlemen. no terminals short to the housing UNTIL you insert a jack. DUH. Pedal doesn't need it anyway, battery's only powering the LED. I guess this particular one is relegated to prototype status now due to the useless jack.

Thanks SO much y'all!!

At any rate, I now have a REALLY cool true-bypasser/feedback looper:

There's a switch to switch between true-bypasser and feedback looper.
There's coarse and fine knobs for feedback amount.
The RG LED turns on when you turn it on. It's yellow for truebypasser and turns AWESOME RED when feedback is engaged.

I'm pleased. Now I just gotta build another one (or three).

Thanks again!
Evan

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Holy MOLY Power Confusion!!