jseymour@medar.COM (James Seymour) (12/28/90)
Since I received no response to my original posting, and it seems to have disappeared, I assume that it fell into the black hole, so I'm re-posting it. I have new information since then anyway. Help! I'm having all kinds of problems with Commodore model 1950 color monitors and/or my A3000. It all started with an intermittent vertical "jitter" I was experiencing with the original unit. Having read some mail here about early units being prone to similar problems, and having a serial number like 845, I got my dealer to swap mine for a new one. The new 1950 has a serial number in the 8000 range (or something like that). The "jitter" remains. Worse, however, is that the new monitor has some new "defects". The screen image (e.g.: WorkBench borders) "grows" (or starts out "shrunken", however you look at it) by about a quarter-inch on the top and bottom of the screen and about the same on the right side. (I don't mean the raster scan area - that totally fills the CRT face.) It also starts out shifted to the left a bit. The monitor needs to be on for over 30 minutes before the image comes close to reaching "terminal size" (it takes about 1.5 to 2 hours to totally stop "growing" and shifting into position). The screen data in the upper-left corner is a bit "fuzzy" during the first few minutes or so as well (almost looks like a convergence problem). Also, the left and right sides of the screen image appear slightly "bowed in" (the left side is quite noticeable), even after "warm-up". Is this normal for these "new" monitors? It certainly is not acceptable in my view. This looks suspiciously like a power supply or horizontal output section problem. The vertical jitter is about one or two pixels worth, affects the entire screen image, occurs at seemingly random intervals, and lasts for seemingly random lengths of time (several seconds or more at a shot). Are these monitors (both old and new) overly susceptible to power-line or "airborne" noise? I've never experienced problems with the power in my house (normal residential area) and the computer equipment is being fed via two Corcom line filters complete with 3-way MOV's for spike suppression. I don't think ground loops could be it as I disconnected _all_ peripherals from the A3000 and the jitter still happens. Since my original posting, I have hooked a power-line disturbance monitor (monitors voltage and frequency and looks for sags, rises, and spikes) and a 'scope to the power line. No anomalies, no noise, power looks nearly perfect. I moved the monitor away from the computer and all other sources of interference, no help. I powered- down the entire house and everything in the computer room, no help. I tried adjusting the "flicker-fixer" while the jitter was happening, no help. I've tried leaving the monitor on for over 24 hours and then powering-up the computer, and vice-versa, to try to determine if warm-up of either had any effect. No help. Behaves the same no matter what. Also since my original posting, the display seems to have "rotated" a bit in the counter-clockwise direction. The color rendition does not seem as good on the new unit either. I'm sorry I made the swap. Replies in technical terms are welcome. I hold an Advanced Class Ham license, and a Commercial License as well, and have over ten years of computer hardware and software experience. -- Jim Seymour | Medar, Inc. ...!uunet!medar!jseymour | 38700 Grand River Ave. jseymour@medar.com | Farmington Hills, MI. 48331 CIS: 72730,1166 GEnie: jseymour | FAX: (313)477-8897
skank@iastate.edu (Skank George L) (12/28/90)
In article <21@hdwr1.UUCP> jseymour@medar.COM (James Seymour) writes: >I'm having all kinds of problems with Commodore model 1950 >color monitors and/or my A3000. It all started with an intermittent >vertical "jitter" I was experiencing with the original unit. Mine does that on green-on-black screens (i.e. SPlot) and the default screen for Tiles. >The screen image (e.g.: WorkBench borders) "grows" (or starts out >"shrunken", however you look at it) by about a quarter-inch on the >top and bottom of the screen and about the same on the right side. Hmmm... Mine has been doing that too lately... It doesn't grow that much (yet). My personal suspicion is that the apparent growth of the screen is due to temperature related design flaws, that is, as the monitor (or possibly the chips in the computer) heat up it causes the display to change. >Also since my original posting, the display seems to >have "rotated" a bit in the counter-clockwise direction. Mine has been like that since I got it. It has occured to me that the problems that I have noticed have been there all along and I have just now noticed them, however, is it possible that my 1950 is dying a slow and horrible death? Will these problems get worse over time or what's the deal? --George