This is Screen-Saver in view mode; [Up]
Date: Sun 19-Jan-1989 15:14:40 From: Unknown Subject: Re: Screen Saver In article <653@wucs1.wustl.edu> smm@wucs1.wustl.edu (Steve Moore) writes: >Does the NeXT cube have a screen saver function? 0.8 doesn't come with a screen saver; 0.9 most probably will. In the meantime, it's a good idea to lower the brightness of the monitor manually. Ali Ozer, NeXT Developer Support >From: dorner@pequod.cso.uiuc.edu (Steve Dorner)
Date: Sun 21-Jan-1989 01:48:15 From: Unknown Subject: Re: Screen Saver In article <653@wucs1.wustl.edu> smm@wucs1.wustl.edu (Steve Moore) writes: > >Does the NeXT cube have a screen saver function? I have not located >one yet and would prefer to leave the cube running overnight if >possible. In the works is an automatic screensaver that will initiate after 30 minutes of idling. I recommended that NeXT engineer an immediate screen blank by hitting the COMMAND DIM key in the same way that COMMAND ATTENUATE on the sound keys (will) initiate mute sound. I think this feature is needed for users to have "some" measure of control over functions, and as a security measure against prying eyes peeking over the shoulder. John Glasscock Indiana University glasscoc@cica.cica.indiana.edu Bloomington, Indiana "I'm a victim of demand-driven desires in a supply-sided economy." Yours truly. >From: kean@mist.cs.orst.edu (Kean Stump)
Date: Sun 23-Jan-1989 19:18:47 From: Unknown Subject: Re: Screen Saver As part of my job, I have to fix ailing electronic devices which seems at this moment to include mundane things like dead monitors, etc. on occasion. I've had quite a few dead monitors or terminals / computers that contain CRT displays in my lab. Nearly always, the thing that goes bad is the CRT high voltage (~10K to 20K volt) anode supply for the display tube. The failure mode is nearly always the same. In virtually all monitors, the high voltage is derived from the horizontal scanning circuitry by ringing choke action. To wit, the horizontal output stage is driving both the yoke of the CRT and the so-called flyback transformer for the power supply. The flyback transformer is [nearly] always coupled to the collector of the horizontal drive transistor through an electrolytic capacitor. The current through the capacitor is often quite large (~3 amps peak at 12 volts). Consumer grade electrolyic capacitors just aren't made to carry sustained large currents for long periods of time (most are intended for power supply filter applications, rather than for coupling power). The capacitors have a tendency to develop short circuits after a while. What is nasty is that the ohmic value is often low, but not zero. Such a condition allows a large current flow from the horizontal power supply into the flyback transformer, but may not blow the power supply fuse. On several occasions, I've seen flybacks that started to smoke, and on one occasion the flyback actually burned. One thing to be wary about most [if not all?] screen saves blank the beam, but don't acutally cut power to the CRT's scanning circuit. Thus the the horizontal is on all the time slowly grinding away at that coupling capacitor. You'll save burning an image into the tube, but the monitor will cook anyway. It seems as if it wouldn't be too difficult to be able to switch off the horizontal drive circuit while the screen was blanked; it would only require one transistor, and the same register bit for beam control would suffice. It would be a lot safer too, as the risk of a fire in the power supply would be elimiated while the monitor was unattended. Note that the CRT heater could remain turned on, so there would be no obnoxious lag when the screen was reenabled. Because we've seen a number of problems with CRTs, our policy here states that monitors on equipment in unattended areas be switched off, not just blanked. I installed a toggle switch on the monitor of my Unix PC at home so that I could leave the computer running for uucp and dial-up while I am here at work. Now, if Next is as cutting edge as they feel, they probably thought about my concern already and are/will actually be cutting the scanning in the monitor rather than just shutting off the beam. (Of course you don't want a monitor fire next to the magnesium cube! :-) :-) ). --Bill >From: johnl@ima.ima.isc.com (John R. Levine)
Date: Sun 30-Jan-1989 21:22:45 From: Unknown Subject: Re: Screen Saver In article <1476@neoucom.UUCP> wtm@neoucom.UUCP (Bill Mayhew) writes: > >It seems as if it wouldn't be too difficult to be able to switch >off the horizontal drive circuit while the screen was blanked; it >would only require one transistor, and the same register bit for >beam control would suffice. It would be a lot safer too, as the >risk of a fire in the power supply would be elimiated while the >monitor was unattended. Note that the CRT heater could remain >turned on, so there would be no obnoxious lag when the screen was >reenabled. > >--Bill I would hesitate to implement this change without careful consideration of all the implications. In a previous life as a broadcast engineer, I learned that the lifetime of a vacuum tube run as a 'hot spare' (with filament on but no anode voltage) is usually much shorter than the lifetime of a tube in normal service. It seems that the hot filament poisons itself if the electrons are not sucked away as they boil off. In the case of RF power tubes, this meant that the tube couldn't deliver normal power because of insufficient cathode current. In the case of a CRT, I would expect a loss of brightness due to the same effect. hess@iuvax.cs.indiana.edu KE9LC >From: greid@adobe.com (Glenn Reid)
These are the contents of the former NiCE NeXT User Group NeXTSTEP/OpenStep software archive, currently hosted by Marcel Waldvogel and Netfuture.ch.