DC jack question

[psiico]

When using a jack of this style wired this way the pin is negative and the sleeve is positive, right? 



So that means I have to isolate the jack from the metal case?

When I put together my Phuncgnosis in the case it wouldn't work.  The battery got hot and drained in a few mintues, obviously a short somewhere.  Was this it?  I also fried the opamp when this happened, could this have been the cause?

[bancika]

Yeah, if jack is metal you need to isolate it from chassis (provided that chassis is also metal and in/out jacks are not isolated) or you can get plastic jacks that don't need to be isolated, like this one

[twabelljr]

When using a jack of this style wired this way the pin is negative and the sleeve is positive, right?

Yes, in the wiring diagram shown it is.
If your jack is metal, then you do need to insulate it from a metal enclosure via a rubber o-ring, plastic sleeve, or one of the other methods described in various threads. If you have continuity from your positive sleeve to the enclosure, then you definately have a short. Smallbear has plastic (insulated) switched jacks that are very nice, but I have had success using rubber o-ring grommets.

[burnt fingers]

I use th plastic ones from smallbear.  They make life so much easier.   

Scott

[Processaurus]

I've always wondered why the standard for pedals was that the sleeve was positive, when it makes sense to do it the other way.  Did Boss do it?

[bancika]

Yeah, it was probably some dumb ass, if center was positive  we wouldn't need either isolation nor wire connecting DC jack tip with ground. It probably doesn't have to do with boss or any other company. It's industry standard for adaptors so they probably just followed it.

[psiico]

I guess that's why it didn't work when I turned it on, I fired the IC.  Lol, well it was my first pedal.  Luckily it's actually a plastic box that I taped up with metal tape, I can just cut it away from the jack.

[guitar_199]

My guess would be that,  when you push a coaxial connector in, you have a tendency to find that center pin first then push it on in.  If the center pin is ground..... that says that your first connection is ground...and THEN you contact power.

[Ge_Whiz]

I've always wondered why the standard for pedals was that the sleeve was positive, when it makes sense to do it the other way.  Did Boss do it?

It's easier to engage the switching function (PSU / battery) with negative earth circuits if +ve is the sleeve.

[Incubus]

I thought it was because when you are using the dc jack to power the pedal, you have no battery in the unit, so the battery snap is just loose inside the unit.

By having the center pin negative and the sleeve positive, when you connect the dc plug into the dc jack, the sleeve, which is 9v, disconnects the positive terminal of the battery snap.

That way, if the positive of the battery snap happens to touch grounded metal casing, it wont short out the adapter because the snap is not connected to the circuit.