campbell@Thalatta.COM (Bill Campbell) (06/15/90)
Sender: Reply-To: campbell@Thalatta.COM (Bill Campbell) Followup-To: Distribution: Organization: Celestial Software, Mercer Island, WA. Keywords: If I turn the monitor off on my system, leave it off for a while, then turn it back on the computer reboots :-( I have used three different VGA boards (MaxLogic, Paradise-16, and Paradise-8 bit) and two different motherboards. Has anybody had a similar experience? -- ....microsoft--\ Bill Campbell; Celestial Software ...uw-entropy----!thebes!camco!bill 6641 East Mercer Way ....fluke------/ Mercer Island, Wa 98040 ....hplsla----/ (206) 232-4164
syd@DSI.COM (Syd Weinstein) (06/16/90)
campbell@Thalatta.COM (Bill Campbell) writes: >If I turn the monitor off on my system, leave it off for a while, >then turn it back on the computer reboots :-( Whats happening is that the monitor being turned back on is causing a noise pulse that is being seen as a reset pulse. Several suggestions: 1. Isolate the monitor, and make sure it doesn't touch the case of the computer. 2. Get a different brand monitor, and a better power supply. 3. Check that the pull up resistor on the reset circuit is proper. 4. don't turn it off :-) -- ===================================================================== Sydney S. Weinstein, CDP, CCP Elm Coordinator Datacomp Systems, Inc. Voice: (215) 947-9900 syd@DSI.COM or dsinc!syd FAX: (215) 938-0235
jeffl@comix.UUCP (Jeff Liebermann) (06/17/90)
In article <4525@thebes.Thalatta.COM>, campbell@Thalatta.COM (Bill Campbell) writes: > If I turn the monitor off on my system, leave it off for a while, > then turn it back on the computer reboots :-( It's your power supply (methinks). A VGA monitor draws mucho amps (1.2A normal, 2.0 surge when the tube filament warms up). If you have a relatively high impedance power line (long power cord, crummy connections, defective surge protector, wacko UPS, dirty fuse connections) on the 117vac, the power line voltage will drop momentarily when your monitor gets turned on. The reason you have to wait a while with the monitor power OFF is to let the filament cool so the inrush current is sky high when you turn it on. You can create the same effect with a high wattage desk lamp, laser printer, or terminal that sucks lots of power when you turn it on. If you want to monitor the effect, put a scope on P8-1 on the power supply DC output connector. The is the "power good" output from the power supply. If this line drops low (0 vdc) from its normal hi (5 vdc) even momentarily ( < 20msec), the mother board will reset and the machine will reboot. Incidentally, the "power good" line was necessary on the original IBM PC with 16k chips which used -5vdc and -12vdc voltages as well as +5vdc. If power was applied in the wrong order, or one of these voltages were missing, the chips would go POOF. Today's dynamic RAM are all run by +5vdc only and the "power good" line could easily be dispensed with. I usually cut this wire from the power supply and pull the P8-1 connection on the mother board high (thru 3.3kohms). As a result, I've been able to tolerate 300msec dropout without reboots or data loss. -- # Jeff Liebermann Box 272 1540 Jackson Ave Ben Lomond CA 95005 # (408)336-2558 voice (408)429-0483 digital pager CIS:73557,2074 # PC REPAIR & RF DESIGN. uunet!comix!jeffl pyramid!vdx!comix!jeffl # universe!milky_way!solar_system!earth!na!us!uunet!comix!jeffl