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Electrickery

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So I just bought myself an MKS50 with PG300 controller.

I have to get a stepdown transformer for the MKS50 as it has an internal 110v PSU.

My question is about the PG300 which just requires a 9V adapter. The supplied US 110V one puts out 9V DC 300mA. I have a 240V one at home that puts out 9V DC 600mA. Will this fry it because it's double the mA? Me no understand mA.

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Also, with the stepdown transformer, I just need to get one that is rated at higher output Watts than what the synth requires (16W) right?

Also also,

Say I get a 500W stepdown transformer, could I then get a US powerboard and power any number of units from it up to a total of 500W?

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Yes, you could buy a 500W stepdown ttranny and a US power poard to power up to 500Watts of 110V equipment. You'll need to get the US power board imported from the states - it's technically illegal to sell them in Australia (well... NSW anyway).

There's only one problem with running 300mA device off a 600mA 9V plug pack. The plug pack *may*, depending on it's design, deliver a higher voltage under low load (less mA). The idea would be to get a multimeter, or find someone who has one, and measure the voltage output when nothing is connected. This will tell you the peak no load voltage. Typically, the more current that is drawn, the lower the voltage goes.

Current is a funny concept to most people. I'll give you an analogy. Put a hose into a 2L container with the hose and container perfectly sealed so no water escapes. Turn on the tap. When the 2L container is full, the flow of water stops. Current is basically the same.

Your device will only pull the current it needs... the same as you will only drink when you're thirsty. Most of the time, it will not pull 300mA even, but at some point it will which is why they give you a 300mA supply. With most new equipment and DC regulated plug packs, you're better off getting a bigger plug pack. The regulation means the voltage will stay within a volt or so of the specified output - e.g. a 9V regulated supply will output between 8V and 10V. Even older designs have about 10% tolerance, so 1 volt either way is fine. Newer designs typically have higher tolerances to voltage variations.

So, summary: Measure the voltage of the plug pack with nothing connected to it. If it's <11V with nothing connected, go ahead and use it. If it's > 11V, head to dicky smith and spen a couple bucks on a regulated power supply of 300mA or higher current rating.

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I'll just buy a 9V 300 mA adapter ;) thanks, JF, for answering both my questions!

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Another electrickery question: I seem to remember it is bad to have any kind of electricity wires, be it extension cords, power cables, adapter leads, etc all coiled up together. Is this right? If so, what is a safe way I can avoid cable spaghetti in the back of my rack?

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Another electrickery question: I seem to remember it is bad to have any kind of electricity wires, be it extension cords, power cables, adapter leads, etc all coiled up together. Is this right? If so, what is a safe way I can avoid cable spaghetti in the back of my rack?

Yeah, electricity running through a wire coil emits electro magnetic radiation. Think about where coils of wire are used: electric motors, speaker drivers, transformers. Another recommendation often made when sorting cables is to never run power and audio alongside each other.

The concerns are the radiation may - just may - show up in your audio.

How likely? Hmm... I'm not majorly concerned, though with car audio, I've always maintained the separate power versus audio paths.

Another issue with tight coils is the wire forms an inductor, similar to that used in an audio crossover that blocks high frequencies from passing through to the woofer. You can imagine why it ain't therefore ideal to be tightly wrapping up those audio cables.

Of greater concern, however, is coiled extension leads carrying quite a load will get quite hot. To prevent fires, the directions always recommend 'uncoil before use'. Secondly, electromagnetic radiation can screw up electronics (ie. hard drives). I had a hard drive become corrupted by a lamp dimmer unit resting right beside the computer tower.

Rather than coil loose cables into a tight circle shape, instead how about gathering them up and laying them back and forth in, say, 1/2 metre lengths?

If the spare length is less than 1/2 a metre, then I'd go with shorter cables, or just put up with the slight disarray.

It's why racks have a front *and* a back: to hide the sins lurking behind. :(

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Not my rack, its backside is bare to the world! Slutty rack. so yeah, bundle but not coil. Cool.

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Actually, the main reason not to coil leads is because they get hot. When they get hot, the insulation breaks down. When the insulation breaks down shorts happen which start fires which kill people and more importantly will burn your gear.

If you're clever about the way you coil leads you can actually REDUCE electromagnetic noise. If you run the cable in alternate loops across itself the magnetic fields induced by the AC current will cancel. It's still not advised as it still creates heat issues (energy is neither created nor destroyed!!) which can still cause a fire.

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Listen to this man, peoples. He's got the engineering degree, not me! ;D

We've got a pretty powerful vacuum cleaner (up to 2200 watts) and the cord gets warm and pliable when run at maximum power during typical use. I hadn't considered it would take the insulation to fail first (allowing the wires to short, spark, ignite) rather than just the insulation catching fire on its own accord. Makes sense now.

Re vacuum cleaners, with their handy retractable cords, this discussion highlights just how important it is to pull out the entire length of cord, even for a small room with a power point close by, just to ensure the heat is able to dissipate from the cord freely.

Great thread title, too! ;)

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^ Totally non-audio but relevant to this, I understand one of the most common mistakes people make at home is running an electric heater off a multi-outlet powerboard or off a long extension lead. Despite the warnings put on the heaters themselves, people don't understand that such a powerful device (my little one is 2400W) will heat up the power leads very easily and as Jester says, wear down the insulation, melt into the carpet or short out and cause a fire.

Winter warning folks - always plug the heater into it's own outlet and never leave it unattended!

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Yep, 2400Watts = 10Amps @ 240Volts. That's the MAXIMUM you're meant to run off a domestic power point. The power points *should* be rated to 16Amps and wired with 16Amp cable into a 16Amp fuse... but in older houses/flats and ones with dodgey wiring jobs they might not be. So, as a general rule, even if you have a double power point it's 1 (ONE) 2400Watt heater. Not one per outlet, one in total... with NOTHING else plugged in to the other side of the outlet.

When you add double adapters and power boards you really are getting into 10Amp absolute peak territory. Most modern power boards have thermal overload cutouts which will trip when the board gets hot from to much being plugged in... however these often fail which will also cause a fire.

Insulation actually has a reasonably high ignition temperature. It's designed that way so it's not often the insulation itself starts a fire - as said earlier it's the failing + short + fire + insulation as fuel that causes a mighty blaze ;) Insulation also tends to self extinguish - it wont burn on its' own. It needs some sort of constant energy input to keep burning such as an electrical fire caused by a short or from a fire in your carpet that started because of the short etc. etc.

The tip on vacuums is actually a good one spec! Most Vacuums are 1500Watts+ these days which is a very decent load (lots of current) + a hot motor right near the retracting coil + the coil inducing heat on itself = fire. The saving grace is that insulation is rated to withstand that sort of abuse in batches of 30-40 minutes no problems at all. The real issues start when you permanently have things coiled drawing lots of current - like a heat attached to an extension lead or a studio run off coiled leads.

Here's a pic of a Power Factor Corrector at one of the sites i look after. One of the capacitors failed and caught fire, derating the insulation and causing the wiring to short... which then melted the contactor below and caused the same set of events and so on for 4 contactors until the fuse finally popped and removed power. The fire department refused to enter the room until the fumes had cleared even with full hazmat suits and breathing devices on - it's that toxic and that dangerous. Once the power was removed from the main feed to the building by the energy people... the firies went in. The ionised atmosphere from the burnt insulation creates a good path for the 1500Amps or so in there being drawn by equipment. In effect, that means just 'touching' the air could electricute you  :wtf: Electricity is such a cool toy  ;)

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:wtf:

What a sight!!! And a mess!! ;D

I'm just finishing off renovating our laundry. With the single power point now sitting above the washer, which is about to be covered by a dryer, I've been contemplating rigging up a power board (hung on the wall next to it) to provide power to the washer+dryer plus an iron etc. as required.

Thinking now that getting a sparky mate in to rig up a permanent hard-wired power strip will be the better - and safer - solution, especially as there's the good chance that the washer and dryer will by running simultaneously with nappy loads during winter.

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:wtf:

What a sight!!! And a mess!! ;D

Sight was nothing - the SMELL was intense. You haven't smelt disgusting ander utterly stomache churning until you've been in a closed room after an electrical fire. There's no way of describing the smell - it's absolutely unique and you never forget it.

I got to spend from 10pm till 5am that day scrubing out breaker enclosures, cleaning walls and circuit breakers to remove all the carbon. The presence of carbon derates the insulation and can fuse the breakers causing more fires and bigger failures (worse case killing someone). So i worked with 5 sparkies and 2 labourers to strip every breaker from the panel and clean it all. The firies even left about 2 inches of water in the bottom of the cabinet where the 1600Amp bus bar runs. Bus bar was above it, but with a bit of heat you'd get moisture on the bar and again derate all the insulating spacers causing shorts and more failures.

Major PITA. Very lucky that one wasn't worse - i've asked all my sites to install shunt trip breakers to their PFC with the trip wired to a smoke detector. That way, if/when the PFC blows up the trip pulls the breaker quickly and stops the electrical fire.

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You haven't smelt disgusting ander utterly stomache churning until you've been in a closed room after an electrical fire.

Or be in the same room as a microwave thats shat itself... that smell still gives me nightmares

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