Date: Thu, 11 Sep 1997 20:21:33 -0700 From: Pius Fischer <pius@ienet.com> To: Doug Russell <drussell@saturn-tech.com> Cc: freebsd-hardware@FreeBSD.ORG, terryl@ienet.com, robert@ienet.com Subject: Re: wdunwedge failed Message-ID: <199709120321.UAA25833@iago.ienet.com>
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Sorry, for the very late reply ... On Thu, 21 Aug 1997, drussell@saturn-tech.com wrote: >On Thu, 21 Aug 1997, Mike Smith wrote: > >>> It flickers. For example, a screen full of these "wdunwedge failed" error >>> messages appears for a second or two and then the screen completely blanks >>> out for a second. Then the error messages are visible again briefly, then >>> the screen goes blank, and so no. Sort of like someone quickly turning the >>> monitor on and off. >> >> It's possibly (as Brett suggested) that some delays in the wd code are >> magically synchronising with something in the display driver, but I'd > ... > > I'd guess either the error messages are just scrolling fast, and end up > flickering, or, especially by the way he describes it, that the video > signal is actually interrupted. > > It may not be the problem, but I would take a multimeter and check out the > +12 volt supply while the machine is in this failed state. The hard drive > most likely uses the 12 volt for spindle motor, etc., and most VGA cards > use the +12 and -12 supplies for the RAMDAC. If the 12 volt line is > really funky (might need a scope to see if it is fluctuating, poorly > filtered due to a dead filter capacitor or something, etc.), the power > supply is the suspect. > > Method B, of course, is to swap in a known good supply, and see if the > problem happens again. :) > > You'd be surprised how many strange problems are caused by a flakey power > supply. Don't ever buy one of those cheapo $30 mini-tower (or whatever) > case deals. The power supply in a $30 case probably isn't too wonderful. > Getting better built cases is an added bonus, too. :) Yes, the power supply was indeed the problem! The voltmeter reading across the bad machine's power supply was a very unsteady 13 - 13.5 volts (if I remember correctly). On a good machine standing next to it, the voltmeter gave a rock solid 12.3 volt reading. We then got a slightly fancier chassis with a new power supply and we haven't seen this wdunwedge/flickering monitor problem again. Another theory suggested that the error messages were scrolling by so quickly that they caused the monitor to flicker. But, in fact, they were coming in relatively slowly, about 1 bright 3-line message every 10-15 seconds (at one point we had the monitor plugged-in when the messages started coming). Also, it seemed unlikely that it was a problem with the monitor itself because the monitor was mostly plugged into another very similar machine, and never exhibited any problems except when plugged into the bad machine when that bad machine was dying. And the flickering already began before the entire screen was filled with bright text. In fact, as soon as the first wdunwedge message came, the flickering began (with most of the monitor still showing dim text). Anyways, thanks very much for all your help and suggestions. Pius
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