Main > Main Forum
Using PC Power supply for 7.5 volt power adapter
dkersten:
I was just thinking the same as ed, if you do this be careful of your grounds or you will just end up shorting out one of your rails. Soon as you plug in your audio jack to the PC you will complete the ground loop and either fry a rail, fry the amp inputs, fry your audio chip, or at the very best have a ground loop in your audio that will cause a hum. If you still want to try it, then before you plug in and after you hook up your power from the PC, meter between the lower part of the 3.5mm audio plug and the jack in the computer. If you are seeing something like 3 or 5 volts DC, I wouldn't try to plug it in, you should see zero if the ground for the audio is isolated from the ground of the PSU.
MonMotha:
To reiterate, while it's possible to get 7V from a PC supply, the reference ("ground") for that 7V is not the same as the reference used by all the guts inside the PC (the black wire labeled "ground"). If you tried to connect them, say, through the audio cable, you'd be shorting the 5V rail out. Given that the 5V rail on a lot of PCs can supply a few dozen amps, you definitely don't want to do that. Melty wires could well result.
The easiest thing to do here is to just get a wall wart and find a way to switch it. Some PC speakers actually need a floating supply. They actually establish an internal reference separate from either of the power input lines and tie the audio ground to it.
If your speakers don't do that, you might find that the speakers work OK on 5V and just won't get as loud.
lilshawn:
---steaming pile of meadow muffin---, you are right. :banghead:
the ground on the power supply and the ground used on the shield of the audio cable are tied together. BZZZT fried cables.
you could plug into the PC through a ground loop isolator though... this separates the ground (and audio) and eliminates the DC path...
http://www.radioshack.com/product/index.jsp?productId=2062214
DeLuSioNal29:
Perhaps I should explain what I'm planning to do:
I'm currently using a recycled PC power supply to power a 60 in 1 board using the molex connector. I have a Jamma harness connected from tbe 60 in 1 to the controls (power wires not connected to Jamma connector since the molex is giving it power). I have an LCD. I have a cheap pair of PC speakers with a power adapter (7.5v). These are all plugged into a power strip. (3 plugs).
I want to power up the arcade by simply reaching in the back and flicking the switch of the power supply. Then all 3 devices will power up. I planned to accomplish this by:
1) Cutting off the power adapter from the speakers and connecting the power cord to a molex connector's +12v and +5v (creating 7v).
2) Splicing the power cord from the monitor (a typical PC power cord) to the power supply plug's terminal inside the power supply. (110v).
3) Leaving the 60 in 1 board plugged into a molex connector and clean up the extra wires/connectors not needed.
I think it should work, since I'm not using a PC with ground. I do have a headphone jack on the 60 in 1 board. Would I fry it if I disconnected it for any reason while the power was on (causing the rail to fry). My main concern (originally when posting this) was that the 7v created from the molex would not be enough to power up the 7.5v needed for the speaker's draw. But now I'm concerned about shorting it out completely.
DeLuSioNaL29
dkersten:
Just save yourself the headache of trying to do all that and get one of these:
http://www.amazon.com/gp/product/B0050HH70E/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1
There are about a million versions of them out on the interweb, many cheaper than this one. You also need to get a fuse for them based on 110 or 220v.
Then take your power strip, cut the plug off, and wire it to that socket.
Now you can use that C14 power cord, have your single switch, and have a power strip with however many outlets you need, and you can use the 7.5v power supply. And you don't have to mount your PSU so it sticks out the back of your cab..
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version