question about 9v plug wiring

[rutledj]

I don't seem to have much luck using the search function here. I get all kinds of messages unrelated to what I'm looking for. Wish there was a way to search ONLY the subject....

Anyway, Can someone point me to a wiring diagram that shows how the 9v jack is wired up? I'm unsure if the center post is positive (which I suspect) or the barrel. If it is the center post, I assume you wire the neg battery wire to the switch on the jack?

Thanks,
Rut

[stinkfoot]

If it's a regular barrel type jack (Boss style), the center pin is negative. The positive is carried on the outside of the plug, and the jack will have two connections for the positive. The battery positive connects to one of them, and the other is the main positive feed to the circuit. When there's no plug in the jack, the battery positive is connected to the circuit. When you insert a plug in the jack, the battery positive gets disconnected, and the positive from the plug is fed to the circuit instead. Obviously, you need to figure out which of the two "barrel" connectors is which (so you don't accidentally feed the adapter power into the battery instead of the circuit). I think you'll find plenty of diagrams over at www.generalguitargadgets.com - almost every project has a parts layout diagram where the power jack most DIY guys use is shown.

The battery negative is wired to the "ring" connection on the (stereo) input jack. This way, the battery will be turned off until you insert a regular mono plug in the input jack (connecting the "ring"/battery negative to ground). Another option is to run the battery negative via the adapter jack's negative connection, and then run the main negative wire from there to the input jack's "ring" connection. That way, the entire pedal will be powerless until you insert the input cable. Also, the wiring will be a little neater (since the positive and negative battery wires will end up fairly close to one another).

/Andreas

[rutledj]

Thanks. That's what I needed. I was thinking the center terminal was positive but since I don't have an adapter yet I wasn't sure.

Rut

[niftydog]

when you do get a power supply it's usually indicated on the case by a little diagram that show's which contact is positive and which is negative.

There is no standard form of wiring for power supplys, but now you know about the Boss style of DC jacks!