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From: braner@batcomputer.TN.CORNELL.EDU (braner)
Newsgroups: net.micro.atari16
Subject: Re: High-pitched whine
Message-ID: <1114@batcomputer.TN.CORNELL.EDU>
Date: Sat, 27-Sep-86 16:50:10 EDT
Article-I.D.: batcompu.1114
Posted: Sat Sep 27 16:50:10 1986
Date-Received: Tue, 30-Sep-86 07:34:40 EDT
References: <860925115730.1.TYSON@ELCAPITAN.ARPA>
Reply-To: braner@batcomputer.UUCP (braner)
Organization: Theory Center, Cornell University, Ithaca NY
Lines: 11

[]

According to Atari (in a memo they sent to dealers), the high-pitched
whine comes from the "inverter" chip, a little DIP on the mother-board
that converts +12V to -12V. It oscillates to do it, ==> whine.  The
only (?) load on the -12V line is the RS232 port and related driver chip
(1488).  So it is not surprising that whatever is plugged in there affects
the whine.  Atari has also sent the dealers instructions on how to eliminate
the whine, which I posted here a while ago.

- Moshe Braner