Question about multiple power supply!

Started by juancra, October 22, 2007, 12:50:01 PM

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juancra

Hi everyone!

I'd just built the Ultra clean power supply at www.generalguitargadgets.com (http://www.generalguitargadgets.com/index.php?option=com_content&task=view&id=134&Itemid=26) but, as i'm not expertise in this kind of buildings I want to make a few question to assure i will not destroy neither my pedals or my house  :P.
First, I used a 220V - 12V 1A transformer, to help reduce the work for the regulator (an LM317T), which is supossed to turn down the 12V delivered by the transformer to the 9v requiered. When I finished it and used the DC meter on one output the power supply, it measured 11.57 volts, is this allright?
In second place, I have a positive ground Ax10G effects unit that I also wanted to feed with this power supply, so I wired an output cable with the tip going into the negative conecctions of the board and the positive to the sleeve. If I connect it with other pedals with negative ground, will be everything allright? .. Is there a chance that a problem happens?

Sorry about my poor english and thanks in advance!
Sebastian

Pushtone

Quote from: juancra on October 22, 2007, 12:50:01 PM

First, I used a 220V - 12V 1A transformer, to help reduce the work for the regulator (an LM317T), which is supossed to turn down the 12V delivered by the transformer to the 9v requiered. When I finished it and used the DC meter on one output the power supply, it measured 11.57 volts, is this allright?


that does not sound right.
I just built the same this weekend and with a 12VAC wall wart I was getting 9.56VDC with close to the stock resistors values.
I didn't have and 2k resistors so I was using 2k7 along with the 274R and 6k8 stock values.

Is your meter calibrated right?  If its a $12 cheapie it may be off but unless you can get to a bench power supply it will be hard to determine that.
Otherwise try some different values for r2a and r2b.
See the thread I started on this build for more info.

Quote from: juancra on October 22, 2007, 12:50:01 PM


In second place, I have a positive ground Ax10G effects unit that I also wanted to feed with this power supply, so I wired an output cable with the tip going into the negative conecctions of the board and the positive to the sleeve. If I connect it with other pedals with negative ground, will be everything allright? .. Is there a chance that a problem happens?


I don't think thats going to work without another isolation transformer. You would need to build something on the order of the Geo Spyder with separate transformer isolated outputs for the pos ground and neg ground pedals.

Can anyone else confirm this suspicion?
It's time to buy a gun. That's what I've been thinking.
Maybe I can afford one, if I do a little less drinking. - Fred Eaglesmith

Somicide

Quote from: Pushtone on October 22, 2007, 01:21:52 PM
I don't think thats going to work without another isolation transformer. You would need to build something on the order of the Geo Spyder with separate transformer isolated outputs for the pos ground and neg ground pedals.

Can anyone else confirm this suspicion?

I can second the suspicion, though memory escapes me as to what post/where I read it.
Peace 'n Love

juancra

I don't remember it exactly, because i populated the board a time ago and finished it today, but I think i've used In4007 instead of the propossed 1n4002 diodes. Can this be the origin of the voltage difference?

Pushtone

Quote from: juancra on October 22, 2007, 02:19:35 PM
I don't remember it exactly, because i populated the board a time ago and finished it today, but I think i've used In4007 instead of the propossed 1n4002 diodes. Can this be the origin of the voltage difference?


No, The 4007 can handle more max voltage but for this application the difference between the 4002 and 4007 does not matter.
It's time to buy a gun. That's what I've been thinking.
Maybe I can afford one, if I do a little less drinking. - Fred Eaglesmith