kenw@noah.arc.ab.ca (Ken Wallewein) (02/19/90)
Pardon me for cross-posting this, but I think it belongs in both places. I just hope I've got the mail address right - I'm not using a newsreader for this. > I have the problem with my 1084 monitor where it snaps occasionally with a > jump in the picture. I read the article about this problem in the > Transactor, and they suggested several things including using a > high-voltage insulating spray. They also mentioned a spot on the bottom of > the logic board which suffers from arcing. I opened up my 1084 to fix this > and discovered that there is a large flat sheet of metal soldered to the > bottom - some sort of shield - which makes it impossible to get at the spot > they were talking about in the article. None of the suggestions they gave > could be applied to my 1084 so I'm out of luck. Has anyone else had a > similar experience? > ________________________ > Bob Fillmore, Systems Software & Communications BITNET: FILLMORE@EMRCAN > Computer Services Centre, BIX: bfillmore > Energy, Mines, & Resources Canada Voice: (613) 992-2832 > 588 Booth St., Ottawa, Ontario, Canada K1A 0E4 FAX: (613) 996-2953 I'd read that article too, as well as various postings that have appeared here. My monitor had been snapping quite a lot, and I'd been quite unsuccessful in determining the location of the spark, even though I could hear it. The article pointed me in the right direction, but I didn't like the solution -- it didn't seem to address the root cause of the problem, which was that the heat sink simply wasn't electrically connected to anything! It picked up a static charge from being in close proximity to all that high voltage, but there was no way for the charge to bleed off. Eventually the charge got high enough to arc, and then the whole process started over. I verified this with a FET VOM (meter), which has sufficient sensitivity that making contact to the metal place after a few minutes of operation caused the needle to jump. Leaving the meter connected stopped the sparking and snapping altogether, even though the current was too low to register. The meter has an internal resistance of 10 megohms or so; it obviously didn't take much conductivity to drain off the static charge. I could have replaced the meter's action with a high-value resistor. However, after using the meter to confirm that the plate had no other electrical connections, I decided to simply ground it with a short piece of wire. Everything has worked properly since. That's it, folks. Ground the plate with a piece of wire and the problem is solved. ----- Another piece of hacking I did on the monitor I don't recommend so highly, but I'll pass it on anyway. By tweaking (read: frobbing) a ferrite slug and a variable resistor, I was able to get the screen to shrink by about an inch both horizontally and vertically (sorry, I can't tell you which ones; I just tweaked until I got what I wanted). I then used 'morerows' to increase the logical size of the screen by nearly 100 horizontally and 40 vertically. It's like having a bigger monitor! ----- Let me warn anyone else who wants to try these hacks; I took a chance. I don't have the schematics, and I don't know if they will cause long-term damage. But I sure like the results. /kenw Ken Wallewein kenw@noah.arc.ab.ca (403)297-2660