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A7N266-VM Case Speaker

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Justice Gustine

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Aug 19, 2003, 1:20:33 AM8/19/03
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The manual has a diagram with "Speaker" and "+5v" going to the case
speaker - just does not seem right to feed 5v through a speaker.

Any explanations is welcomed!

TIA


--
Lower your cable bill! http://careers.comcast.com/choices/searchlocations.asp

Gene Puhl

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Aug 19, 2003, 2:11:36 AM8/19/03
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Justice Gustine <justice...@yahoo.com> said:
news:qnc3kvspm301v4qcl...@4ax.com:

> The manual has a diagram with "Speaker" and "+5v" going to the case
> speaker - just does not seem right to feed 5v through a speaker.
>
> Any explanations is welcomed!
>
> TIA
>
>

The +5V indicates the positive output (the red wire)
It'll be OK.


--
Gene P

Ed

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Aug 19, 2003, 2:28:46 AM8/19/03
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On Mon, 18 Aug 2003 22:20:33 -0700, Justice Gustine
<justice...@yahoo.com> wrote:

>The manual has a diagram with "Speaker" and "+5v" going to the case
>speaker - just does not seem right to feed 5v through a speaker.
>
>Any explanations is welcomed!
>
>TIA


Speakers have polarity.
Connect the red speaker wire to +5v and the black speaker wire to
ground, usually this is one connector from the case front panel and
easily connects to the pins on the mother board.

Ed

Paul

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Aug 19, 2003, 7:58:03 AM8/19/03
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In article <qnc3kvspm301v4qcl...@4ax.com>, Justice Gustine
<justice...@yahoo.com> wrote:

> The manual has a diagram with "Speaker" and "+5v" going to the case
> speaker - just does not seem right to feed 5v through a speaker.
>
> Any explanations is welcomed!
>
> TIA

There will be some limiting impedance in the circuit tugging on the
speaker lead. It is like the speaker is the load of an open collector
circuit or something.

See page 95 of this 486 motherboard reference schematic:
http://www.amd.com/epd/desiging/evalboards/all/22408/22408.pdf

Basically, the PC case speaker driver looks like this -

+5 /
| __/
|_____|
_____ SPKR
| |__
| \
/ \
\ 33 ohm
/ resistor
\
|
| C
B | /
_______|/ 2N3904
|\
| \
| E
|
-----
--- GND
-

The 33 ohm resistor limits the current in this example, but if
the speaker leads were shorted, the resistor would probably get
burnt.

I've read one account of the +5 wire to the speaker being pinched
between the PC case cover and the chassis, resulting in a short
to GND. This burnt the wire. A safer design would be to split the
current limiting resistor in two, and put half on each side of the
speaker header.

HTH,
Paul

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