jimt@tekig4.TEK.COM (Jim Tallman) (03/19/87)
My Mac+ video started wiggling on the right side intermittently. A colleague's went to a horizontal line (the vertical quit). (Or it could be the other way around; I can't remember on his.) We opened his and jiggled stuff until we found the connector from the crt to the video board wasn't connected well. I believe it's marked J1. Wiggling it would make his vertical work and break depending on where it was held. We resolder it back in and his works fine. I went home and re-soldered mine. Both have been working for about two weeks and mine isn't showing the intermittent problem. I'm so thrilled, because I was worried it would go out during use at some unpredictable time. It may come back, but it usually came about every day. So if you're having video problems like the icons "shaking" you might consider trying re-soldering the same connector before shelling out the coin for a new board. It worked for two out of two. Caution--be sure to have power off. I unpluged mine. Could be dangerous stuff around crts. My chance to give something back to the net! regards, jim
straka@ihlpf.UUCP (03/20/87)
Yes, this procedure seems to be common for the Mac. The tech who installed my disk and ROM upgrade resoldered the harness connections on my analog board (for good measure). They evidently crystallize with time due to the heat factor. I would like to add that it is very important not to fart around with the 2nd anode potential which goes to the CRT (the big wire that goes on the side). It can hold a charge for hours (days?), and be quite a shock. Easy solution: ground a screwdriver with a test lead (eg with alligator clips) to a major metallic part of the Mac chassis; then gently insert the grounded screwdriver under the rubber cap until it shorts (don't touch the metal part of the screwdriver, or you'll still get zapped). This is standard procedure when working with ANY CRTs in the consumer field and hasn't ever hurt any circuitry that *I* am aware of. Note that a lesser, secondary charge can develop and give a lesser, although still substantial shock. Redo the above just before touching anything close to that second anode. This is serious stuff, and can cause DEATH if done in an incorrect manner by someone naiive to electrical circuits. Be CAREFUL if you touch these kinds of things at all!! I have worked with this kind of stuff on and off for 20 years, and still feel nervous when working around ANY high voltage (I got zapped by a color TV 2nd anode once in high school). I like living. Are you ALL clear on this? (I hope so; I think I just beat it to death!) -- Rich Straka ihnp4!ihlpf!straka