From owner-freebsd-hackers Tue Jan 9 13:46:48 1996 Return-Path: owner-hackers Received: (from root@localhost) by freefall.freebsd.org (8.7.3/8.7.3) id NAA09772 for hackers-outgoing; Tue, 9 Jan 1996 13:46:48 -0800 (PST) Received: from irz301.inf.tu-dresden.de (irz301.inf.tu-dresden.de [141.76.1.11]) by freefall.freebsd.org (8.7.3/8.7.3) with SMTP id NAA09758 for ; Tue, 9 Jan 1996 13:46:36 -0800 (PST) Received: from sax.sax.de by irz301.inf.tu-dresden.de (8.6.12/8.6.12-s1) with ESMTP id WAA10876 for ; Tue, 9 Jan 1996 22:46:31 +0100 Received: by sax.sax.de (8.6.11/8.6.12-s1) with UUCP id WAA21486 for freebsd-hackers@freebsd.org; Tue, 9 Jan 1996 22:46:31 +0100 Received: (from j@localhost) by uriah.heep.sax.de (8.7.3/8.6.9) id WAA00405 for freebsd-hackers@freebsd.org; Tue, 9 Jan 1996 22:37:43 +0100 (MET) From: J Wunsch Message-Id: <199601092137.WAA00405@uriah.heep.sax.de> Subject: Re: Dual Monitor Systems... To: freebsd-hackers@freebsd.org (FreeBSD hackers) Date: Tue, 9 Jan 1996 22:37:42 +0100 (MET) Reply-To: joerg_wunsch@uriah.heep.sax.de (Joerg Wunsch) In-Reply-To: <199601091040.LAA21892@allegro.lemis.de> from "Greg Lehey" at Jan 9, 96 11:40:36 am X-Phone: +49-351-2012 669 X-Mailer: ELM [version 2.4 PL23] MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit Sender: owner-hackers@freebsd.org Precedence: bulk As Greg Lehey wrote: > You've obviously never burnt out a monitor :-( > > Running monitors out of spec *does* damage monitors. The usual cause for burning a monitor is _over_driving its horizontal frequency. In a dumb fixed-frequency monitor, the CRT accelerator voltage supply is simply done by the horizontal output stage (``line transformator'', like in any TV set), and overdriving its spec'ed frequency causes this stage to produce way too much high voltage, and finally too much power dissipation in the driving transistors, hence overheating either the transistor(s), or melting the isolation out of the transformator. _Under_driving the frequency has the ill side-effect of reducing the high voltage, which is far less dangerous. If a monitor is operated in this state for a really long period of time (weeks), this might also cause the cathode of the CRT to become `deaf' (reduced emittability), but that's certainly not a problem if it's running a few hours in this state. Running a fixed-frequency monitor (f[H] usually between 60 and 90 kHz) at VGA speed (31.5 kHz) is plain underdriving. (``multi-sync'' monitors have a separate accelerator voltage power supply, or some other sort of self-control, and usually protect theirselves against overdriving.) > ..., but what > happens if you have a power fail in the middle of the night, and > something hangs? I don't turn off my computer, but i turn off my monitor when i'm absent for a while. -- cheers, J"org joerg_wunsch@uriah.heep.sax.de -- http://www.sax.de/~joerg/ -- NIC: JW11-RIPE Never trust an operating system you don't have sources for. ;-)