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Topic: OT - Need electrical help... (15 msgs / 212 lines)
1) From: Angelo
Hi,
I know that you guys have great knowledge about things 
electrical/electronic, so I'm asking for some info.
I need to get an external power adapter for an out-of-production 
synthesizer module I have.
The specs in the manual call for the following:
"9 VAC, 5 Volt Amps external Transformer".
The 9vac I understand, but what is "5 volt Amp"? I just need to know 
the amperage rating , right? Can you figure it out from these specs...
Any help would be greatly appreciated...
Thank you,
Angelo

2) From: Michael Mccandless
Try Goodwill.
5va = approximately 5 Watts.
P or, I=P/E
P=Power in Watts
I=Current in Amps
E=Voltage in Volts
I=5/9 or .56A  (560 mA)
The higher the Amp rating, the cooler it will run.
The load will only draw what it needs, so anything over 600 mA should be OK.
McSparky
On 10/27/06, Angelo  wrote:
<Snip>

3) From: Timothy Wat
What kind of synth module is it?  I'm a keyboard player, and have always had
good luck with the guys at Sweetwater Sound (www.sweetwater.com) to take
care of me, even with obsolete parts like this.
Tim
On 10/27/06, Michael Mccandless  wrote:
<Snip>
-- 
Timothy Wat
timothywat

4) From: Aaron
Angelo.
volt amp,  roughly is  volts times amperes....  since you already know 
the volts 9... you have to figure out  9 times what will equal roughly 5....
say about 600 milliamperes.  (ok not exact but you always want a little 
head room) if it takes 5 va you want a power supply that supplies a bit 
more than this so you are not running it at 100 % it's capacity all the 
time.   They run cooler and last longer.
Radio shack sells a universal adapter that is good for an amp or so that 
should be oh maybe 20 bucks most??  You can select the voltage on it, 
and select the tip to use,  there are a few models and they have a whole 
rack with different tips to choose from so it plugs into your item 
properly.   If need be, bring your thing in with you and you can compare 
to make sure you have the right tip for it.
Aaron

5) From: Angelo
Tim,
I actually have two units that use the same adapter. They're the 
Alesis Nanosynth and Nanobass. I'll be using the Nanosynth with an 
EWI 4000s windcontroller.
  I'm not really looking for original equipment, but rather a Radio 
Shack multi voltage/tip unit. I just needed to know the minimum 
miliamps needed...and thanks to you guys, I do :-)
Ciao,
Angelo
Btw, I've dealt with Sweetwater before and they are good...
<Snip>

6) From: Michael Dhabolt
Angelo,
Be sure to check polarity.
Mike (just plain)

7) From: Michael Mccandless
Make sure it is AC.
McSparky
On 10/28/06, Michael Dhabolt  wrote:
<Snip>

8) From: raymanowen
Thrift stores usually have a rat's nest of these "Power adapters" or "Wall
warts" hanging somewhere, or they're in a box or drawer somewhere near the
electronic doo-dads.
If you need to save $$, a 12-13vdc adapter would work.
Cheers -RayO, aka Opa!
Got Grinder?

9) From: Michael Mccandless
A DC adapter may or may not work.
Depends on hot the AC is rectified.
The spec calls out an AC adapter.
McSparky
On 10/28/06, raymanowen  wrote:
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10) From: Dean
The OP says the manual wants "9 VAC, 5 Volt Amps external Transformer"
A lot of wall bricks are DC as indicated in ray's post.  Just in case 
you thought it was gonna be easy. ;-)
Dean  
raymanowen wrote:
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11) From: raymanowen
I made my previous comment because your music box already has an internal
rectifier and filter capacitors. If the synthesizer waveform generators are
voltage critical, the internal power supply (5VA !?!?) already has a voltage
regulator chip in it.
9vac rms will give 12vdc (+) when it's rectified and filtered, so if you
can't find a 9vac 1/2amp (+) adapter, many others will work, including DC!
(The waveform generators sure don't work on AC even in China.)
Cheers -RayO, aka Opa!
On 10/28/06, raymanowen  wrote:
<Snip>
"When the theme hits the bass, I dance the Jig!" - -Virgil Fox at the Mighty
Wichita (ex- NYC Paramount) WurliTzer- 1976

12) From: Michael Wascher
No, the DC produced from 9VAC will depend on the type of rectification used
- half wave, full wave, doubler ... all produce a differnt DC voltage.
Best to just stay with the specs, and find a 9VAC source
On 10/28/06, raymanowen  wrote:
<Snip>
-- 
"In theory, there is no difference between theory and practice; In practice,
there is."
  - Chuck Reid

13) From: Angelo
I was under the (mistaken?) impression that polarity wasn't an issue with AC...
<Snip>

14) From: Michael Mccandless
I've learned to avoid  assuming that a circuit may be designed a certain
way.
There's no end to the possibilities.
Inputs to power supply circuits aren't always as straight foreward  as one
might assume.
Some may contain series caps, etc.
Without a schematic, or visual perusal, it's not a good idea to connect non
conforming to equipment.
It will most likely work 99% of the time, but Murphy has a way of finding
that 1% when least expected.
McSparky
On 10/28/06, raymanowen  wrote:
<Snip>

15) From: Aaron
Angelo, in conventional thinking polarity generally isn't... or wasn't 
an issue with A/C  however, given that many devices have floating 
grounds, swaping polarity can potentially give one a nasty shock if they 
were to touch two a/c devices where one was wired up with the wires 
swapped.  Swapping the hot lead and the neutral lead can cause problems 
in some devices.
With a wall transformer like your device needs, were only talking 9 
volts, and that 9 is it's own totally isolated system, so it's a non 
issue there, but for stuff that just 'plugs into the wall'  yes, 
polarity is an isuue.
Aaron who is saying "neutral is NOT ground"


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