need help in converting an adapter

[nkrypt]

Hi,

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?


Thanks

harish

 

[Don Bowey]

Hi,

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?


Thanks

harish

The only practical way to use it is with a 9 volt series regulator, which
will drop the 12V to 9V. Google for "series regulator" or "9V power supply"
to see the applications. The three-terminal devices use only a couple
capacitors to complete the circuit.

Don


Don

 

[DaveM]

Hi,

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?


Thanks

harish

First, make sure that your wallwart has a DC output.
Second, does the wallwart contain any filtering after the rectifier? If
not,you'll have to provide it. Use the rule of thumb: 2000 uFd per amp of
current.

Download the datasheet for the LM317 from
http://www.jameco.com/Jameco/Products/ProdDS/192268.pdf. On the first page
there is a schematic that shows the simplest arrangement for this regulator.
That should suffice for your needs. After construction, just set R2 for Vout of
9 volts.
Be sure to mount the regulator on a heat sink that can handle at least 5 watts.
Provide ventilation for the heatsink (don't enclose the heatsink in a sealed
plastic box so that air can't circulate around it).

You can find everything you need at www.jameco.com.
LM317:
http://www.jameco.com/webapp/wcs/st...toreId=10001&catalogId=10001&productId=192268
Heatsink:
http://www.jameco.com/webapp/wcs/st...&catalogId=10001&productId=326721&pa=326721PS

Cheers!!!!!
--
Dave M
MasonDG44 at comcast dot net (Just substitute the appropriate characters in the
address)

Some days you're the dog, some days the hydrant.

 

[psdayama]

Hi,

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?


Thanks

harish

Very simple method is to add 4nos. 1N4002 diodes in seires. Also a
elco can be
put on the 9V output. It will work with amplifier. These dont require
much regulated
supply.

 

[Don Bruder]

Hi,

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?


Thanks

harish

You'd be better off just buying a regulated 9 volt 1 amp wall-wart and
going from there. (Yes, I saw that you said 850 mA - That's the minimum
to safely run the beast without burning up the power supply - The device
will draw what it actually needs, and that's all it'll take)

Diddling with DC voltage/amperage "adjustments" such as what you're
looking for just isn't worth the headache when there's a "canned"
solution available on the shelf, probably for less than $20.

 

[Don Bruder]

The only practical way to use it is with a 9 volt series regulator, which
will drop the 12V to 9V. Google for "series regulator" or "9V power supply"
to see the applications. The three-terminal devices use only a couple
capacitors to complete the circuit.

Yeah, that would work, but what about the (relatively) high current
rating he wants? Most of those three-terminal (Most likely 78XX series
devices) regulators start getting pretty iffy (if they don't just plain
cook off immediately) above about 600mA. Under 500mA or so, they work
just peachy, but above that point they just don't seem to cope very
well, according to my experience. (Heavy-duty heatsinking can help, but
even with that, they don't usually seem to last very long)

 

[Homer J Simpson]

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?

http://www.allelectronics.com/cgi-bin/item/PS-913/480/9_VDC,_1.3_AMP_POWER_SUPPLY_.html

 

[Ryan Weihl]

Hi,

I am newbie with basic electronics knowledge,I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?


Thanks

harish

so get a 9V wallwart that is capable to deliver 1A (a litle reserve)
and make sure its AC or DC (whatever your equipment needs) and if DC
make sure you get center + or - , again whatever your euipment needs.
rw

--

 

[Radiosrfun]

so get a 9V wallwart that is capable to deliver 1A (a litle reserve)
and make sure its AC or DC (whatever your equipment needs) and if DC
make sure you get center + or - , again whatever your euipment needs.
rw

Yeah really! By the time you even crack the case on the 12v 2 A job, you
could have the one you need wired up! They're only like $7 or so. Hell, if
you lived in the neighborhood, I'd swap you what you needed for the one you
have.

L.

 

[nkrypt]

Hi Guys,

Thanks for all the tips, I guess what you people say is right. I
Googled for a 9v 850ma adapter and its priced at $14.95 with shipping,I
just thought i might save a few bucks by using this old adapter I had
lying around. I think I shalll go ahead and buy that one if its such a
bother to hack this one.

Thanks a lot

Happy holidays

harish

 

[psdayama]

Hi Guys,

Thanks for all the tips, I guess what you people say is right. I
Googled for a 9v 850ma adapter and its priced at $14.95 with shipping,I
just thought i might save a few bucks by using this old adapter I had
lying around. I think I shalll go ahead and buy that one if its such a
bother to hack this one.

Thanks a lot

Happy holidays

harish

Looks like U are chickened out sissy boy!
U will spend only 20 cents on diodes and 10 cents on a Elco. U dont
need to open
the case of wallwart but put this all in small matchbox size veroboard.
U can spend reamaining $14s on something good matter.
Otherwise I am sure U R nothing better than a person who is afraid to
switch lest
he gets electrocuted !!!!

 

[Homer J Simpson]

Thanks for all the tips, I guess what you people say is right. I
Googled for a 9v 850ma adapter and its priced at $14.95 with shipping,I
just thought i might save a few bucks by using this old adapter I had
lying around. I think I shalll go ahead and buy that one if its such a
bother to hack this one.

Be aware that you don't need one rated exactly at 850 mA. Any amount above
that is fine, and 1 amp are common - and cheap. I can buy those for $10 at
my local 'dollar and more store'.

 

[Radiosrfun]

Yeah, for the money - if they have "regulated" available, snatch them up -
you're better off. Instead of paying "shipping" - LOOK AROUND! Surely
someone in your area sells them - and cheaper than the $14.95.

Lou

 

[psdayama]

Looks like U are loudmouth.

U know nothing from LED and you know nothing from wall-wart output
at 850mA. Could be EZ 15-16V. 4 diodes drop 3V, leaves 12V on 9V
amp input. 3V of 9V = +30%, NOT GOOD.

Goodbye, blowhard boy.
JF

It shows Ur knowledge ! Just calling anybody names doesnt put U
on saintly
pedestal. How do U know that 12V adaptor gives 15-16V on load?
All walwarts are having internal impedance which drops 12V to 9V on
full rated
current. Also commercial amps dont requires so precisely regulated
supply like
digital systems. So good bye and go on blowup jobs.
People like U are just curse on this forum.

 

[psdayama]

On 12 Dec 2006 08:55:35 -0800, "psdayama" <psdayama@gmail.com>
But I guess it's ok, monkey-boy, for you to call someone a chicken
sissy-boy and get away with it? **** you _and_ your double
standard, you hypocrite.

You zombie U **** urself. When I called someone sissy it was for
incompetence
of bugger to take simple job. People half smart like U encourage that.
If anybody has
double standards it is U moron with shallow knowledge and loud mouth.


THIS SHIT SITE DID U VISIT? Click and check Urself loudmouth.
I know that because I have manufactured 100s of them.

More important, how come _you_ don't? You sit there making a lot of
noise, pretending to be some kind of expert, but in truth you don't
know what you're talking about. About LEDs _or_ wall warts.

What I am saying is my proffesional experience of 30yrs. That may
be equal
to Ur age. Also I am alumuns of great institute known world over.



YES I HAVE MEASURED IN MANY ! TWICE OF UR AGE!!
What do U know of amplifier design? Just because U don't know
abt
LEDs and wallwarts U start thinking as expert of amplifiers?
Those amplifiers will work very happily with wallwart having excess
capacity
and poorly with less capacity- mostly giving hum and clipping
distortion.
Sp many speaker amplifiers are working without any regulated supply.
If amplifier is built with those ICs then they work with 15V without
problems.
The aim of discussion is to find most economical solution for
person and not
show ones prowess of misguiding.

---
Really? I've been here for a long time and I've helped a lot of
folks over the years, and yet you've only been here for two weeks or
so and have already been shown up for the nasty-assed little fraud
you really are.

May be I have come here late but I see that people like U with half
baked
knowledge are misguiding. U dont have solution to problem but only
taking
swipes at somebody who can
Put up a list of peoples acknowledment to whom U have helped. U
think
that just being a bozo on some site means U are the only expert in
world?
All Ur comments I have seen here are nothing but bullshit. U are
feeding
people with ur shit.

 

[Stanislaw Flatto]

Hi,

I am newbie with basic electronics knowledge,

How about so basic:

12-9=3
3V/~1A=~3Ohm----> 3.3 very standard number
3V*1A= 3W----> Any 5W or bigger should do(don't touch, warm/hot)

On the other side, if this equipment is intended to run from car lighter
connection it should be able to withstand variations of +-20% from what
is written (maybe more). I have a CD "walkman" labeled 9VDC and on
opening found that the capacitors inside are 16V. so it works as music
supplier during long trips directly connected to lighter socket.
KISS is smart using of electronics.

I have an wall wart that
provides 12v 2A as output i would like to some how reduce this to 9v
850ma to power an amplifier system. Can any one point me to the
schematic for this?

Schematic is trivial, performing "remont" on a wall wart is "sadistic"
chore.

Thanks

harish

Have fun

Stanislaw