chris@suntan.ncsl.nist.gov (Chris Schanzle) (08/24/90)
gilstrap@aslan.sbc.com (Brian Gilstrap) writes: >Configuration: >------------- >Mac Plus >Problem (Started about three days ago): >-------------------------------------- >The screen suddenly goes black and after a light tap on the right side of the >mac, the screen comes back. Typically, applications are not bombed but do >end up losing data (e.g. cumulative scores in a game go back to 0). EXECUTIVE SUMMARY: I would say you have one of two choices: Resolder pins 1 and 3 on J4 (the high-voltage connector on the Analog board) or have it replaced for around $200. After having one of our Mac Plus's analog board replaced for $208 for the simple "video collapses to a single, vertical white line", when it collapsed on yet another mac (but this time to about a 1/2" wide line), I decided I didn't want to get packed again. If you're around many Mac Plus's, the first order of business is to pick up a copy of "Macintosh Repair and Upgrade Secrets" by Larry Pina. It should tell you everything you need to know. Second, the Analog board get hot when the mac has been on for an hour or more. Combined with cooling a few hundred times, the solder joints will crack and exhibit flaky behaviour. Third, replacement parts are available (at somewhat reasonable prices; four transistors and two capaciters were $25 including shipping) through Soft Solutions. In fact, I think that's all these guys do. Anyway, give 'em a call at (503) 461-1136 and describe your problem to them. What follows is what I got out of a telephone call trying to find their description of the *problem* of a 1/2" wide vertical line rather than the more common pixel-wide vert. line. Naturally, it was the last one on the 24-symptom list. :-) [Note: Some symptoms/solutions have been omitted. KEY: T1 is the main flyback transformer, "C"s are capacitors, "Q"s are transistors, "U"s are IC's. ] For screen jiddering and worms, replace T1, T5-T16. Ringing noises, replace T1. Completely Dark -- Resolder pins 1,3 on J4, Replace U2, replace Lag chip on logic board. Horizontal Line: Resolder pins 5, on J4, Check Q1, Q2, Int Q4, R2, R3. Pin-prick in middle: reconnect crt cable. Shakes -- always solder connections Q1 and Q2. Inspect and resolder them. Half black -- resolder connections Q1, Q2. Distorted right side -- flyback C1; coil magnets on tube. Black screen, clicking CR5 and filter capacitor. Magnified -- Bu406d, Q3. Causes C1, possibly T1 to fry. (caused by low voltage ) ** my problem Wide band in Middle. Replace and check Q1, Q2, Q4 Q5, and U1. Q1 is MSU01 transister, Q2 is MPSU51 transister, Q4 2M4401 transister Q5 2N5485 transister, U1 (Mac SE only) is 74LS38N =================== BIG DISCLAMER FOLLOWS: (this is serious, but almost fun!) NOTE: Obviously this means taking your Mac apart and soldering. Don't do this if you don't think you can be careful enough -- you can die from current held in capacitors at the high voltages found inside a monitor even after turning off the computer. You should learn to drain this current before pulling the back cover. Although I had never taken a Plus apart to this degree (I have installed RAM), I was EXTREMELY careful and survived -- and the Mac Plus was fixed. I have had lots of previous experience soldering. You be the judge of your capabilities; don't sue me if you made the incorrect decision. ____________ "If you can read this, you're not Chris Schanzle looking through the Hubble telescope." chris@suntan.ncsl.nist.gov