Author Topic: Amplifier - switched + and - ?  (Read 1490 times)

Offline Dolby

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Amplifier - switched + and - ?
« on: June 19, 2015, 03:39:04 PM »
Hi,

Hoping someone can assist.

I've got an internal amplifier from a subwoofer (pretty much a circuit board - no pretty box) and I need to plug the power into it. I've identified the two pins (+ and -) - but I'm not sure which is which?

Will it blow something up if I get it wrong?

Offline fuz940510

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Re: Amplifier - switched + and - ?
« Reply #1 on: June 19, 2015, 04:02:31 PM »
Nope, but instead of the cone firing (moving) forwards, it will fire backwards
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Online Crankshaft

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Re: Amplifier - switched + and - ?
« Reply #2 on: June 19, 2015, 04:23:53 PM »
You got to get the polarity correct for the input power.  Doesn't matter for the driver.

+ is positive.
- is negative.

Are you referring to the point where AC mains must feed, or is do you have a power supply.

If the marking are +ve and -ve, then it is either the speaker output or a DC power input.

The last thing you want to do is put AC mains into the speaker outputs.

If it's an AC input, polarity is not applicable.  But then it wouldn't be marked + / -.




Offline 2wice

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Re: Amplifier - switched + and - ?
« Reply #3 on: June 19, 2015, 04:52:12 PM »
I think he's referring to the power (AC or DC) in.

Are you powering straight from wall (AC)?
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Offline Dolby

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Re: Amplifier - switched + and - ?
« Reply #4 on: June 20, 2015, 10:26:54 AM »
Yea - AC straight from the wall. I'll take a photo soon.

Don't want to blow anything up

Offline fdlsys

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Re: Amplifier - switched + and - ?
« Reply #5 on: June 20, 2015, 10:32:54 AM »
Either post a photo of the whole PCB so that the connectors/solder points and markings on the PCB are clearly visible, or take the PCB to any neighbourhood shop that has anything to do with electronics; anyone should be able to tell you where the AC goes in and where the speaker connects.
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Offline Dolby

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Re: Amplifier - switched + and - ?
« Reply #6 on: June 24, 2015, 04:33:31 PM »
Sorry for the delay.

I've attached the ones where I think power goes (but no idea + or -)

Also - heres' the whole board https://goo.gl/photos/vXSq35HuhSbXaBFB9 - but I'm sure power from AC goes opposites sides of the fuse



Offline fdlsys

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Re: Amplifier - switched + and - ?
« Reply #7 on: June 24, 2015, 06:13:48 PM »
You should have posted a photo of the whole board. For an amp of that power chances are the PSU is not even on the board.
The four building blocks of the universe are fire, water, gravel and vinyl. Dave Barry
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Offline JANNAS

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Re: Amplifier - switched + and - ?
« Reply #8 on: June 24, 2015, 09:07:07 PM »
Looks like Neutral to the right of the fuse and hot (live) to the left. The smps looks like it is on the board as well.

Offline 2wice

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Re: Amplifier - switched + and - ?
« Reply #9 on: June 24, 2015, 09:11:15 PM »
If AC it should not really matter does it?
Trenton Carr
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Offline JANNAS

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Re: Amplifier - switched + and - ?
« Reply #10 on: June 24, 2015, 11:22:12 PM »
On a transformer or resistive load it should not matter but I'm not sure about smps's. Better keep with the designers preferred wiring.

Offline YT

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Re: Amplifier - switched + and - ?
« Reply #11 on: July 09, 2015, 11:19:17 PM »
Hot is positive put a small fuse 500ma so u cant fry the board and check
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Online Crankshaft

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Re: Amplifier - switched + and - ?
« Reply #12 on: July 10, 2015, 11:22:47 AM »
There is no positive and negative with AC.

Hot is live.  In fact it makes no difference if the item is not earthed.

I'm very concerned about the confusion and mis-information in this thread.