Date: Thu, 17 Feb 2000 07:44:58 -500
From: Tom Rutherford <[EMAIL PROTECTED]>
Subject: Re: silencing the modem?
On 16th Feb 00 at 2.02am, Nettamer List <[EMAIL PROTECTED]> wrote:
NL>Date: Tue, 15 Feb 2000 17:59:56 +0000 From: "Michael L.
NL>Dawley" <[EMAIL PROTECTED]> Subject: Re: silencing the modem?
NL>On Tue, 15 Feb 2000 07:34:11 -0500, Nettamer List wrote:
NL><snip>
NL>> NL>It's a Hayes Optima 288 VFC+Fax and it must be quite
NL>rugged as > NL>I spent the first week after I bought it
NL>second hand failing > NL>to get it to work until I
NL>substituted 9v AC for the 9V DC I'd > NL>been using <g>
NL>> Well, if it's a Hayes, you couldn't buy one new if you
NL>wanted it. Maybe > in a still shrink-wrapped box from a
NL>warehouse somewhere, the way I > bought my Courier, but not
NL>exactly new. At any rate, yes, most modems > require AC. I
NL>can't remember what the details are, but the AC is used > for
NL>some kind of timebase, I do believe. It's been that way since
NL>the > old Commodore VIC-20 days. They always piped 9vac to
NL>the user port, > specifically for modems that plugged in
NL>there.
NL>> -- 73 DE Tom Rutherford, N8EUJ, Burton, MI Hello Tom, all:
NL>I took my Hayes Accura apart once, and noticed a big heat sink
NL>attached to an SCR transistor, an wondered what it was there
NL>for. Then, when I got a Hayes 9VAC adapter for it, I realized
NL>that the AC to DC conversion was taking place right inside
NL>the modem, and in fact, when the modem is on, the top of the
NL>case gets warm where the SCR is located. Also, the adapter
NL>has an output rated at 800 milliampheres, which is quite
NL>high, and is needed to handle the big AC to DC setup inside
NL>the modem. On silencing the modem: I have a Viking V.90 56K
NL>Speakerphone/ voice modem, and it's quiet all the time since
NL>I do not have a speaker plugged into the back. If I wanted to
NL>hear it, I could get a plug and run it to the sound card
NL>input, or something. Thanks, Michael L. Dawley Pearl,
NL>Mississippi Bobcat, Net-T, Arachne, etc.
Well, Michael, what you found inside was not an SCR. Probably not a
transistor, either, although it's entirely possible that Hayes could've
actually built a series pass regulator on the board. It would've been
easier to grab an off-the-shelf component like the National
Semiconductor LM-7805 or a generic replacement. That's an all-in-one
fixed regulator that will handle an output current of 1A. They could've
used an LM-317 adjustable regulator, too, which handles an amp and a
half. But, the AC has to be there for some reason. Not sure what.
800ma isn't that big, really. Now, if it had been 8 amps, that's big.
:-)
-- 73 DE Tom Rutherford, N8EUJ, Burton, MI
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