question on grounding

[mikechang]

Hi all:

i got a newbie question again on grounding.....

now that im done with the circuit and other component of this clean booster
im trying to put everything into the home depot electrical junction box
but things seem to not grounded properly......
when i have the input/output/power jack mounted onto the box and plug in the power (im not using the 9v battery, so i don't even have the 9v battery holder)
the thing doesn't turn on.... i assume it's the Vdd got connected to gnd through the power jack (metal) by contacting with the box.....
this got solved by not mounting the input/output jack or power jack onto the box....

and the power supply im using is the outter shell = 9v, inner pin = GND
so i think when the power jack is mounted onto the box, the outter shell part is connected with the box
and the box got grounded through the input/output jacks.....

my question is.... could i be right about the "power jack mounted onto box = outter shell connected to the box" part??
and i really need a good way of solving this.......

thanks a lot

[petemoore]

  Probably a jack wiring..there's a buncha different hard to ID/Describe jacks you can use for input jack power defeat trick [only one kind works], and you need a 1/4'' mono phono plug in it to work.
  Whatever power switching the jack/plug does can be tested and drawn on paper or remembered, all possible 'positions' is what needs tested [for this that'd be just plug in/plug out]..the tip always goes to/toward the circuit [through the bypass switch or straight in] the input HAS to goto the guitar the output to amp or other input. Obvious and very easy to overlook.
  Voltage measurements may help us help you, a good time to read then re-read the debugging thread when soon/when you've got time.
  Voltages w/ power, resistances and connections without power, no test better than the other...you never know which one will tell you something first.
  Esp. if grounding problems, before adding battery, check for short between V+ and V-, continuity tests between to 'where V+ is supposed to go' and V+, same tests for V-.

[slacker]

my question is.... could i be right about the "power jack mounted onto box = outter shell connected to the box" part??
and i really need a good way of solving this.......

That sounds like what is happening. If you use a metal DC jack with 9volts on the outside connected to a metal box that is connected to ground then you short out the power supply. You could solve it by reversing the connections to the DC jack and reversing the polarity of the power supply, that will give you 9 volts on the inside of the DC jack and ground on the outside. Obviously you won't then be able to use the power supply for other pedals.
Another solution that I've used is to drill the hole for the DC jack bigger than it needs to be and then screw a piece of plastic over the hole and mount the DC jack to that, so it's not touching the box.
The best solution is to use plastic DC jacks like these http://www.smallbearelec.com/Detail.bok?no=93

[dxm1]

my question is.... could i be right about the "power jack mounted onto box = outter shell connected to the box" part??
and i really need a good way of solving this.......

This is likely. In a sane world, running a positive DC voltage through a barrel connector would put ground on the outer sleeve, with the 'hot' lead on the somewhat protected inner contact. Many female barrel jacks are designed with this in mind. The metal ones, especially, have the outer sleeve connected to the metal body to allow grounding to the chassis.

For us, BOSS et. al. have decided to reverse this wisdom, and run the hot lead on the sleeve. One way to avoid shorting the positive lead to a metal chassis is to use only all plastic DC jacks. If, for some reason, you must use a metal jack, you will have to insulate it completely from the metal chassis (usually not an easy task).

Best bet is to use only plastic DC jacks.

[mikechang]

ok....i guess i'll go look for a plastic DC jack then....

kinda sux now cuz im only one step away from making my first pedal......
what's a local store that might carry a DC jack for not too expensive?? (i live in San Diego if anyone does btw)

i think the radioshack carries the metal type.... but not sure about the plastic type.....