Power supply help

Started by Phrog, July 20, 2010, 07:13:27 PM

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Phrog

Hello Frosties :) I've just received my Digitech Brian May Red Special guitar pedal which I ordered from Germany. (I'm in the UK). Because of this, my 9v power adapter on my pedal board does not fit the power adapter socket in the pedal, so I have to use the European plug provided through an adapter, which is a pain in the arse. Now, to remedy this I'm thinking about getting one of THESE so my power supply will fit. However, on the German plug provided, it says that there is an output of 1.3A, whereas my power supply has an output of 100mA.

 If I plug my power supply into the pedal, will bad things happen?

Drarok

Do NOT take just my advice, wait for someone more knowledgable to confirm, but I think that devices will pull whatever power requirements they have, so if you tried a 0.5A power supply on a device trying to draw 1.0A, it'd wreck the power supply.

If the PSU can push 1.0A and the device only attempts to pull 0.5A, no worries.

Again, please wait for someone else to confirm/debunk this. :)

Phrog

Thanks Drarok. Having done a little more research, it seems i just need a new power supply (as well as the size adapters). Would it be fair to say that you're OK as long as you have more than or equal the amount of amps required?

Pedro

Again, I'm no expert but I agree that if the voltage and polarity are right then the gear will draw what it needs.
I'm not sure that plugging in an underpowered power supply would wreck the power supply necessarily. Power supplies tend to have protection against such things (overload, short-circuit and the like)...but I wouldn't leave it connected for long when trying it. ;)

I think having more amps available is good, it will run cooler etc. But still need an expert....

Hmm, never a Hippo around when you need one!
"Putting food on the table is more important than 7/8"

Phrog

Cheers Pedro. I've also read that 30mA is'nt enough to make a difference, but I'm not sure I trust that. Turns out power supplies are expensive, too! I can see why I went for the cheapy 100mA one in the first place now. This always happens when I buy something expensive, there's always another expensive purchase waiting round the corner to come and kick you in the arse in order to make the first one work!!

Brom

All the observations here seem to be fine. Yes, equipment will draw only the amount of current it needs, so you can run stuff from any power supply that is giving the correct voltage as long as it is rated in terms of current (or power, i.e Watts) equal or above what your equipment needs. It's the voltage that has to be correct, and of course the correct polarity. If you run something from the correct supply voltage but with insufficient current capability, the voltage output of the supply will drop and the thing you want to work will start doing strange things or not work - however, stuff in general is not damaged by running at a lower voltage.

A perfect example is the mains in your house. The socket on the wall provides 240V but comes from a massive powerstation which can provide thousands of amps, everything you plug into it is designed to run at 240V so there are no problems with regard to current. Then along comes half time at the FA cup final, and the end of Eastenders or Coronation Street and every man and his auntie puts the kettle on... then thousands of amps are drawn. If this goes unchecked and the current or power limit of the supply (powerstation) is exceeded and the voltage will start to drop. To stop this happening the main control room of the national grid has the TV on continuously so that they can predict when high demand is likely and can switch in reserve or even buy some off the French to cover our unique passion for tea!! - This effect only happens in the UK!

So, as long as your power supply is delivering the same voltage as your gizmo wants and has a current rating above or equal to what is required by the gizmo, everything is fine. THE most inportant thing, after getting the right voltage is to get the polarity right, check and double check - even buy a cheap meter, more things are blown up by incorrect polarity than anything else!
I am out of the office. Messages can be left with Mr. C Lyons on 020 7722 3333

Phrog

Thanks Brom. In the end it's turned out that I'll have to use more than one power supply in any case because the new pedal works with AC rather than DC (is that what polarity means?). Order for new DC adapter duly cancelled, and disaster averted. I'll just have to stick with the pain-in-the-arse setup.  :roll:

Either way, thank you all for your kind help and expertise! Without you lot I probably would've just thundered on and ended up breaking things. :)

RacingHippo

Hmm? Whassat?

Wot Brom sed.
And Drarok. And Pedro.

Check how much current Brain May pulls - it should say on the back/bottom. I hope he's in a good mood when you go looking for it. Or it should be in the manual.
You need a power supply that supplies at least that much current. More is fine. Less will either make your power supply trip out (hopefully temporarily) or fry the power supply. You can't supply too much current.

Also check that your power supply is DC regulated (some are AC, but they're rare)- it'll have this symbol on it:


To check the polarity of the connector on the power supply and on the pedal, see if you can find one of these symbols on them or their manuals:



If they match, you're cooking on gas. I mean electricity.
If they don't, you'll be cooking on a pedal.


I've heard that story of Brom's before, that there's a bloke whose job is to watch telly and throw a switch to bring additional French power online after Eastenders (a regular "TV Pick-up"). Blowed if I can find reference to it online though. But I did find The top 10 TV pick ups :)

Oh, and for the pedantic, the UK is officially on 230V. It probably measures 240V really but it really is 230v, honest, and has been ever since the supply was "harmonised" with the rest of Europe (who are on 220v) - all they did was widen the voltage tolerance to 230 V ±10% (207 V to 253 V).
Fascinatin'.
Almost.
* May contain nuts.

Brom

Quote from: "Phrog"the new pedal works with AC rather than DC (is that what polarity means?)

Yes, DC (Direct Current) always has a positive and negative - the current always flows the same way through the wires.
AC (alternalting current) the current flows forwards then backwards and as such the voltage accross the terminals keeps changing and inverting. So there is no polarity.

As RH said, AC adaptors are not often used, so please double check that you need an AC supply.

 :)

Quote from: "RacingHippo"Oh, and for the pedantic, the UK is officially on 230V. It probably measures 240V really but it really is 230v, honest, and has been ever since the supply was "harmonised" with the rest of Europe (who are on 220v) - all they did was widen the voltage tolerance to 230 V ±10% (207 V to 253 V).
Fascinatin'.
Almost.

Well, I didn't know that. I've always assumed we were served up 240 Volts of the Realm. 230 ohh no, sounds far too odd and European - not to mention Chinese dentist time.

Thanks for the enlightenment!
I am out of the office. Messages can be left with Mr. C Lyons on 020 7722 3333

Tricky

//ftp://ftp.digitech.com/pub/PDFs/Manuals/Artist/Brian_May/RS_Manual_Final.pdf says that the thing runs off 9VAC
That's just weird  :?
Is that normal for this sort of kit, or just a misprint?

But like Brom says, if its AC then polarity isn't an issue.
When the future\'s looking dark, we\'re the ones who have to shine...

RacingHippo

Quote from: "Phrog"... the new pedal works with AC rather than DC (is that what polarity means?).
You posted that when I was writing my diatribe ;)
I've checked that user manual online and indeed it says:
Quote6. POWER SUPPLY JACK
Connect only the included PS0913B
(9V AC) power supply to this jack.
Note that the Red Special Pedal is
not equipped for battery power.

Being AC would explain why it's not batteriable.
So there ya go.

Try one of these: http://www.maplin.co.uk/Module.aspx?ModuleNo=43055
* May contain nuts.

Phrog

I have the AC adapter that came with the pedal which works fine, the issue I was trying to solve (when I still assumed it was DC I needed) was running all my pedals off one power pack, which obviously I can't do if Brian is demanding AC power. I thought the issue might've been because it came from Germany, but obviously that was just my inner Basil Fawlty bubbling up to the service  :mrgreen:

Mouse

Quote from: "Brom"get the polarity right

I'm sure Jon Pertwee could reverse it if need be.


johninblack

Ideally you want a power supply that will provide all the current you need + 10%. That gives you a supply working well within itself and not getting too hot thus shortening it's (and possibly in very remote cases the equipment connected to it's) life.
"F#?K OFF, GRANDAD!!!!"