Fix your expensive Boss PSA AC adaptor

[R.G.]

i'm not an electrician and don't know much about it, but i know that ac still has pos and neg. if i plug my LED line tester into the power point it will only work one way, and my dmm will give me either +240v or -240v. what about grounding things like amps though where it's pretty much crucial? pardon my extreme ignorance... i am curious though

You are pardoned, you asked a good question.

AC does not have a polarity, as it by definition alternates between + and - instantaneous polarities. AC has phase.

If you have only single-phase AC in your house, then you only have an alternating +/- and there is no good reason to differentiate between either side of the AC line. At least that's what they thought back in George Westinghouse's day. Westinghouse was the guy who promoted AC for power distribution. Edison wanted to use DC. The found out that AC with no reference to the real physical earth is (a) dangerous and (b) more expensive to ship around on wires.

So utilities universally tie one of the otherwise-floating sides of the AC power line to a copper wire which runs from the top of the power pole to the bottom - 6' underground. One side of the AC line is tied to the earth back at the power pole. That means that one side of the AC line doesn't vary up and down with respect to the planet itself. We call that the "neutral" side. The side which then wobbles up and down is the "line" or "hot" conductor. This was thought to be safe.

Until they found new ways to die with it. With this two-wire AC line, if you have a fuse or a switch in the neutral side, the equipment can still be charged with the switch off or the fuse blown, and you can still die by touching something grounded and the equipment. So we added a third wire, a safety ground wire. Safety ground carries no current in the non-fault case, and is never switched. It remains connected to ground as long as the equipment is plugged in.

Your LED line tester is set up to tell you the difference between AC neutral and AC line.

All two-wire AC adapters/wall warts plug to the AC neutral and line, and have no switching or fusing that is user accessable, and no connection from secondary to AC neutral, so they do not need safety ground as long as the y pass stringent arc-over voltage tests in the range of 3600-4200V. Anything connected to the secondary is either grounded separately or is assumed to not need a solid earth reference. Many things do not.

There is a lot to grounding that I have already typed into many posts here. Search for "ground" in posts by me.

[The Tone God]

Here are some gut shots of a Boss adaptor:

Top

Left

Right

Andrew

[remmelt]

AC does not have a polarity, as it by definition alternates between + and - instantaneous polarities. AC has phase.

Thanks! I really needed that... I always knew there was something to AC but never found someone who could explain it clearly enough. Super!

[darron]

r.g...... you've outdone yourself as always. thank you very much for that! exactly what i wanted to know.

(:

[stm]

RG's explanation should be archived in the Wiki or FAQ.

[MikeH]

Until they found new ways to die with it. With this two-wire AC line, if you have a fuse or a switch in the neutral side, the equipment can still be charged with the switch off or the fuse blown, and you can still die by touching something grounded and the equipment. So we added a third wire, a safety ground wire. Safety ground carries no current in the non-fault case, and is never switched. It remains connected to ground as long as the equipment is plugged in.

This is why you never, ever, ever, ever, should plug your refrigerator into a 2 prong outlet using an adapter.  If the fridge gets a short the entire chassis can become electirified and when you go to open it and grab that last brewski- bam.  Good bye.

[allan_belt]

any schematics available? 

[duck_arse]

http://www.diystompboxes.com/smfforum/index.php?topic=104739.0

there's really not much to it. took me longer to find the thread than it would take you to build one.