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From: TYSON@SRI-STRIPE.ARPA (Mabry Tyson)
Newsgroups: net.micro.atari16
Subject: High-pitched whine
Message-ID: <860925115730.1.TYSON@ELCAPITAN.ARPA>
Date: Thu, 25-Sep-86 14:57:00 EDT
Article-I.D.: ELCAPITA.860925115730.1.TYSON
Posted: Thu Sep 25 14:57:00 1986
Date-Received: Fri, 26-Sep-86 20:57:03 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 24

I had no problems with the high-pitched whine described by some people until I
plugged a generic null-modem onto the cable attached to my RS232 port.  When
I removed the null-modem, the whine would stop.  It wasn't always there when
the null-modem was attached.  (I don't think the problem was related to the
particular device attached to the other side of the null modem.)

The null modem passed pins 1 and 7 through, swapped 6 with 20, swapped 2 with 3,
and tied 4 and 5 (same side) together and fed them to 8 (on the other side).
The null modem was symmetric (ie, it looked the same from both ends).
I'd guess the problem was because 4 and 5 were tied together.  

I have since constructed my own null modem that did only the pin switching that
I needed.  It is connected to the same device as before.  The whine is no longer
around.

Moral: if you have the high pitched whine, unplug your RS232 cable (if any) and
see if it stops.

By the way, I've had my 1040ST since March and have only powered it off about
4 times (mostly because of power failures).  I've had no problems with
overheating (room temp is usually 65-80 degrees F).  I chose to try rarely
power cycling my 1040 as a way of minimizing component failures.  So far I have
had no problems (but this is only one sample!).  I do turn off my monitor when
it is not in use.