mdeale@vega.acs.calpoly.edu (03/15/89)
Hello folks, recently we've been having problems with one of our Sun 3/50's. A Sun (?) technician while here fulfilling a service contract on a different machine was asked why the screen blinks/flickers. He said that the problem is static electricity -- it builds up and when it discharges the screen blanks momentarily. Not an altogether satisfactory answer especially when he goes on to say there's nothing we can do about it until the monitor breaks and we have to buy a new one. Any comments on the cause of the problem or solutions would be appreciated. Cheers and thanks, Myron #mdeale@polyslo.calpoly.edu
jbn@glacier.STANFORD.EDU (John B. Nagle) (03/20/89)
Sun had problems with their monochrome monitor supplier in the early
Sun 2 and Sun 3 days. Sometimes the high voltage would arc over, blanking
the screen and occasionally crashing the system. But I thought this was
fixed by 1986. Are these very old units?
John Naglemyers@hpfcdj.HP.COM (Bob Myers) (03/22/89)
> recently we've been having problems with one of our Sun 3/50's. A Sun (?) >technician while here fulfilling a service contract on a different machine >was asked why the screen blinks/flickers. He said that the problem is >static electricity -- it builds up and when it discharges the screen blanks Two possibilities come to mind; unfortunately, only one gives you any hope of any easy fix. Assuming that by "blinks/flickers", you mean that the video simply "goes away" for a short period of time, there may be a break somewhere in the video signal path. Look for a defective cable or connector between the monitor and its driver, or (less likely) there may be an intermittent contact - such as a tiny PC trace cracking - on the video amplifier board itself, or between the video amp and the CRT base (the CRT connector). The other possibility is a common one with CRT displays, particularly ones which are fairly new or have been recently subjected to some sort of mechanical shock. This is "flashover", and it's what I suspect the tech was actually referring to. It's not really caused by "static"; in flashover, a defect in the structure of the electron gun, or some small bits of debris within the tube, can provide points for momentary high-voltage arcs within the tube. This may be accompanied by a "snapping" sound as the tubes blanks, and/or visible arcing in the neck of the CRT. If it's a gun defect, the only solution is to replace the CRT. If it's debris, the offending particle is often "burned out" by the arc. Debris particles are always present to some extent when the tube is new, or may be "knocked loose" (phosphor flakes, etc.) if the unit is jolted. In either case, they will usually work their way back to the neck and be burned out over a few days or so of normal use. If the problem persists longer than a week, with no sign of decreasing frequency, you should assume that the tube is bad and is in need of replacement. Bob Myers KC0EW HP Graphics Tech. Div.| Opinions expressed here are not Ft. Collins, Colorado | those of my employer or any other {the known universe}!hplabs!hpfcla!myers | sentient life-form on this planet.