Possible to convert DC to AC?

[jimbob]

I have a lot of 9v dc adapters but i need a 9v ac adapter. Any easy way to do this?

[casey]

it'll be cheaper just to go by one.

time is money.

[The Tone God]

Easier too. You would need something like an inverter which means finding a circuit, building it, testing it, etc just to save a few bucks which you wouldn't really save in the end since you would need more parts to build the circuit which means time and money. Plus you would not be able to to generate volt for volt AC from DC. There would be losses.

Andrew

[Paul Marossy]

If you can get the wall wart casing apart successfully without ruining the insides, then all you would have to do is bypass the diode bridge and filter cap (if one is present) and "voila!", you have an AC wall wart.

The hard part about that is getting the shell apart. Maybe you could use a Dremel tool equipped with a cutting wheel and cut it at the seam very carefully. Do your mod and then glue the case back together with super glue or something like that. That's the approcah I would take. With the right tools, it could be done within a 1/2 hour.

[cd]

If you can get the wall wart casing apart successfully without ruining the insides, then all you would have to do is bypass the diode bridge and filter cap (if one is present) and "voila!", you have an AC wall wart.

Er, not quite.  I don't know how rigid your requirements are (do you need EXACTLY 9V AC?) but if you bypass the rectifiers, one of two things will happen:

- if the adapter is regulated, you'll probably end up with 9VAC.  The regulator needs more than 9VDC to do its magic (usually 11V or more).  9VAC rectified to DC gives you 12.6VDC, which is enough for a 9V regulator.
- if the adapter is unregulated, you'll probably end up with something like 6.5VAC, which rectified to DC is 9VDC.

Either way, I'd just go out and buy a 9VAC adapter  Easier, cleaner, less hassle!

[Paul Marossy]

Man, sometimes I do the dumbest things! Yeah, I forgot about the diodes bumping up the voltage...  :oops:
Wall warts are rarely regulated, though. Maybe the trick would be to find a 12VDC adapter in a thrift store and do as I suggested. That would give you somewhere around 9VAC. I find 12VAC adapters quite often at thrift stores, I can pick one up for about $1.00 usually.

Of course, the easiest thing to do is just buy a 9VAC wall wart. I'm sure someone must make one...

[travissk]

I've been looking for a 9VAC 500mA supply for the past week. I have checked two Best Buys, two Targets, Wal-Mart, two Radio Shacks, and all I have come up with, both at Radio Shack
-12 to 18V AC adapter
-9V AC, 300mA, wrong plug type

Both are horribly overpriced. I'm talking $20-30 for an AC adapter. If I wanted to get screwed that bad, I would have ordered the official one from Digitech in the first place  :lol:

Then I looked in the mouser catalog and found part number 412-209051. It's 9V, AC, 500mA, and is only $5. Unfortunately, it has a 3.5mm phone plug instead of the barrel plug that I need, but it's looking like the best option for me right now. Paul, this might be an option for you to consider. Page 1240 in the new (blue) mouser catalog.

I'm also in need of a power supply for a Digitech Whammy (IV/reissue). I lucked out and got this along with a Line 6 FM4, both needing repair, and I'm hoping that the Digitech just has a failed power supply as is often the case with those things. Unfortunately, it's 9V AC, 1300 mA, so even cutting and resoldering the right connector isn't an option. Stupid Digitech and their proprietary power supplies

So, any of you have any suggestions on where to get these things?

[Paul Marossy]

travissk-

Regarding small AC transformers, I would normally just buy one from whatever source had one since money is not that tight for me. I was only suggesting one way to possibly find one for cheap. That's a good price. Mouser has just about everything, don't they. I have ordered lots of stuff from them.

I know what you mean about proprietary stuff. It is kind of aggravating.  :evil:

[travissk]

Paul -

Yes, if I knew the Radio Shack adapter would have worked out-of-the box, I might have bought it since time is money and I could afford it. I meant that the 9V AC transformer from Mouser would work great for you if you needed a 3.5mm plug and haven't found the correct adapter yet.

Where it gets confusing is that I thought you were the one looking for the adapter, not jimbob... my bad :lol:

So jimbob - if the 3.5mm plug is what you're after, or if you're willing to make a converter, check out that adapter at Mouser.

Since I'm in KC for the summer, I can tell you to rule out the following places:
-The 2 Wal Marts at 119th+metcalf, 135th+State Line
-The 2 Best buys at 119th+metcalf, Bannister Mall
-The 2 Radio Shacks at Oak Park Mall and 119th
-Targets at the same locations as the wal-marts
-Ebay - none listed right now

I haven't really been actively searching since the pedal only set me back $20 and I'm fully expecting to resell it or adding memory and messing around with the EEPROM (it's a Digitech XP200 Modulator). I've just run into places when I'm out, on the way home from work, etc.

[Paul Marossy]

No problem Travissk.  :wink:

[Paul Perry (Frostwave)]

A good USA mailorder place for AC trannys is www.jameco.com (get the printed cat, it is easy to miss stuff in the web catalog).
And, if you do try combining an AC ands  DC supply, have a good long think about what is happening with the earths of the 9v and the AC gear.. you might be suprised when you connect it all up & switch on :evil:  :oops:  :roll:

[travissk]

Thanks! I can't believe I forgot about Jameco, looks like they have exactly what I need.

jimbob - here's the page with all the AC adapters.
http://www.jameco.com/cgi-bin/ncommerce3/ExecMacro/jameco/home.d2w/report?cgrfnbr=778&ctgys=503;528;778;

[Transmogrifox]

For 500mA, a lossy inverter is an easy build.


Use a ~30VDC supply ( easy to cannibalize off an older printer from salvation army for a couple bucks )

...Here's the part that I know is unorthodoxed:  Capacitively couple the input of an opamp through a 120:9 (9VAC--->9V RMS--->~12V amplitude--->~24 Volt peak-peak) resistor divider to the 120 VAC output, reference neutral to your opamp V/2 (12V) reference, and reference that whole thing to earth ground (chassis) and buffer the output through a 2N3904, or even a TO-22 package type tranny for kicks and giggles and there you have it in quite a backward way.  This will safely source 500 mA.

+ terminal of 9VAC source now is transistor buffer output.  - terminal is neutral (V/2 reference).

It's kinda weird, but it would work.

If you don't know how to design this circuit, then you're best off keeping up the search for a CE approved 9V AC adapter.