Home made AC-AC power supply question

I have a device requiring 9v AC 2.5 Amp.

So do I get a 240v-9v transformer from the electronics shop and put it in a case, attach the correct leads and I'm done.

I suppose an inline fuse might be a safety precaution.

Is this all that's required or is there some sort of regualting curcuit that I should add?

Tranformer I was thinking of using

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Reply to
Clubsprint
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Yes. The fuse should be in the live (not neutral) line. It should be a lot less than 2.5 amps, of course, because it's on the high voltage side (before you've traded volts for amps). Try 0.5 amp slow-blow.

Regulated AC is very uncommon. Your device probably does its own regulating.

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Whoa... None of those is rated to deliver 2.5 amps. The biggest is 2.0 amps and will overheat in your application.

What kind of device are you powering and what was its original power source?

Reply to
mc

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The device I'm wanting to power is a Rocktron Chameleon Pre-amp. It says 9v AC 2.5 Amp on the back. But the manual says 2.0amp.

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Do you think I should look for something larger? Maybe 3A? Thanks for the advice on the fuse.

Reply to
Clubsprint

How about this one with the secondaries inn parallel?

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Reply to
Clubsprint

Let's see...

It's a preamplifier, so its power consumption is not going to vary much.

Can you supply it with power and see how much current it actually draws, using an AC ammeter? I have no idea whether to believe the manual or the panel markings.

Glad to be of service!

Reply to
mc

That's a fine transformer but more than you need. (One of the secondaries by itself would be sufficient.)

When paralleling secondaries, be sure to use a voltmeter to check phasing. For example, suppose A1 and A2 are the terminals of the first secondary, and B1 and B2, of the second secondary. You propose to connect A1 to B1 and A2 to B2. To perform the test, go ahead and connect A1 to B1 but do not yet connect B1 to B2. Instead, connect an AC voltmeter to B1 and B2. If you see a very small voltage or none at all, go ahead and make the connection. If you see double the secondary voltage, one of 'em is backward!

Reply to
mc

You're taking the fun out of it! :)

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Reply to
Jamie

I was wondering about this, however, shouldn't I measure the voltage between A2 and B2 and if there is double the voltage that would mean that they are wired in series? There is a smaller toroidal transformer that supplies 9v at 3.3A with the secondaries in parallel.

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I'm thinking rather than make an external power supply that I'd install it in the unit if there is room.

Reply to
Clubsprint

"Clubsprint"

** Buy an approved plug pack with that rating.

** No - that is not safe.

** Fuses save equipment from fire - not people from electric shock.

The transformer you have cited is not safety approved for use as an external PSU.

It is not short circuit proof and it does not have a thermal fuse.

Buy a 9 volt AC plug pack - it will cost far less anyhow.

Idiot.

...... Phil

Reply to
Phil Allison

YES! (Oops!) My mistake. Measure between the 2 that you are about to connect, and if there is a large voltage, don't connect them.

That sounds like a suitable transformer. But I'd put it in a separate case because this is a sensitive preamp and might pick up hum from the transformer magnetically.

Reply to
mc

Those are not especially easy to find, hence his question.

By extension, are all people who build their own power supplies idiots?

You do point out an important advantage of "wall-wart" type transformers -- that, in general, they are designed so that when short-circuited, they either do not overheat, or burn out without generating enough heat to start a fire. However, with reasonable precautions (fuse, enclosure, etc.) I don't think what this fellow is proposing to do is dangerous. He's only going to use it with a specific preamplifier, not connect it to things at random. And he's building one unit, not applying for safety certification.

Reply to
mc

I know, I know. But only when it comes in contact with your body.

Do you have laws in Australia against building electronic equipment? Strange.

Reply to
mc

And you are being an ass. Safety first. You keep wanting to hurt or kill people.

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Reply to
Michael A. Terrell

Excuse me? At what point have I ever threaten to hurt some one?

Those kind of remarks can lead you into something you wish you never stepped into.

Making accusations of a serious nature is really not the route you want to go.

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Real Programmers Do things like this.
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Reply to
Jamie

You dumb piece of shit do you believe everything you read. I have a box of wallwarts behind me and the majority of them are just a fuse and a transformer. Any asshole can get a UL or other agency approval sticker and stick it on there product. Read a paper once in a while. There's more to life then trolling and molesting Kangaroos.

And nothing is 100% short cct proof.

The 350W SMPS on my PC has UL ,CSA Approval but yet it lacks a proper EMI filter, and looks like it was soldered by a twelve year old. The silkscreen is there for the CM choke as well as Y-caps but they aren't. Do you think this is "short cct. proof"? The supply is an ANTEC these are the geniuses in SMPS design scary.

If you're that paranoid, use redundant protection, Fuse, polyfuse active current limiting, multiple MOV's. Size your transformer for what you design your current limit for.

Hey Phil I just built some short cct proof PSU's. I'll ship some to you free.

Reply to
Hammy

"Hammy the Fuckhead " "Phil Allison"

** LOL - not even a single word from you is to be believed by anyone.
** That little transformer is kinda special, though.

If not, it CANNOT be sold in Europe or Australia inside a plug pack - as every new plug pack design must be submitted for stringent safety test and formal agency approval before going on sale.

Each one sold top the public gets a code number which MUST be printed on the unit so the approval can be tracked to the equipment maker/importer and the agency that supplied the certificication.

The OP is in Australia, in case you missed that important detail.

** You are nothing but a know nothing, lying septic tank asshole.

One of the countless many.

** Which is NOT a plug pack transformer.

** You have not got even the * tiniest clue * what this is all about - f*****ad.

SMPS are not even part of the topic - you MORON !!!

FYI:

A inherently short circuit proof transformer is one that by design will NOT overheat and damage its insulation even if the secondary is shorted indefinitely - obviously only fairly small ones can do this.

Others normally rely on a thermal fuse ( means opens at a set temperature) embedded in the primary winding to disable the transformer in case of a sustained overload or fault developing in the any of the windings. They also have special insulation and construction that prevents a dangerous situation arising for the user under all the usual failure and accidental overload conditions.

Yet others again use fire-proof insulation & special construction to prevent any possibility of the primary winding contacting the iron core & frame or the secondary winding even IF the unit burns out due to overload etc.

The vast majority of general purpose transformers offered for sale by component dealers have only basic insulation & no special safety oriented design features.

They are only safe to use inside equipment that has no metal case AND no connectors going to external devices OR else all secondary side circuits are directly linked to the AC supply safety ground.

...... Phil

Reply to
Phil Allison

I bet your mommy tells you your special. Do you have your special helmet on?.I dont think you could handle more brain damage.

Who regulates this Phil the respective goverments. That will probaly slide right over your helmeted head too.

Must be a long waiting list for wal warts,considering they are all undergoing stringent safety tests. You actually belive that every single PSU is tested.WOW your guilible.

You miss my point f****it! A small quantity is submitted for testing ,not everyone. If you believe that every single PSU is tested you are the idiot! They rely on the integrity of the company, usually chinese and they couldnt give a f*ck about your regs.Toy recalls ring a bell asshole.

Like I said if you watched the news once in a while,you'd know that what is submitted for approval is'nt what always winds up on the shelf.

I couldnt give a shit. He does have my sympathy though because you also live in Australia.

Your the top of the heap in that department assjam .

To stupid to get my point again asshole!Snipped away the relevent bit .

The offer still stands!

Right back at you . Stick to battery operated 555 timer ctt.s ass before you hurt yourself

Who you quoteing here Phil. Are you incapble of independent thought.

Was the expalanation of what a polyfuse is for your benifit,or did you not notice it when you C/P someone elses work.

Insert Phils rambling here----

Yes all nice and good but how many that actually make it on the shelf actually conform to these standards. Like I said dont believe everything you read.

Happy googling dipshit.

Reply to
Hammy

"Hammy the Septic Tank Cunt "

( snip the maniac's absurd, paranoid crap)

** Killfile this spamming CRIMINAL pile of sub human garbage.

NOW !!!!

Before any more of it's putrid droppings pollute your mind.

....... Phil

Reply to
Phil Allison

Amid the volleys of verbal hostility here, did anyone solve the OP's actual problem -- where to get a 9-volt 2.5-amp wall wart? He couldn't find one, which is why he wanted to know about building his own power supply.

Reply to
mc

Like you are doing right now? Look, this is a beginners newsgroup, where most posters have no idea of how to work safely and your stupid, off hand comments don't help. What you think is funny can get someone killed, because they don't understand.

Also, if you're going to make threats, MAKE DAMN SURE YOU CAN CARRY THEM OUT.

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Service to my country? Been there, Done that, and I\'ve got my DD214 to
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Reply to
Michael A. Terrell

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