need help in converting an adapter

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

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

You can find everything you need at

Cheers!!!!!

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.

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.

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)

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.

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

Radiosrfun wrote:

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 !!!!

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'.

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

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.

You zombie U f*ck 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 S*IT SITE DID U VISIT? Click and check Urself loudmouth. I know that because I have manufactured 100s of them.

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!!

systems.

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.

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 s*it.