Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site peora.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!hjuxa!petsd!peora!jer From: jer@peora.UUCP (J. Eric Roskos) Newsgroups: net.micro.mac Subject: Re: What part fails in power supply? (a repeat) Message-ID: <1934@peora.UUCP> Date: Mon, 27-Jan-86 09:20:09 EST Article-I.D.: peora.1934 Posted: Mon Jan 27 09:20:09 1986 Date-Received: Tue, 28-Jan-86 06:08:32 EST References: <1899@peora.UUCP> Organization: Concurrent Computer Corporation, Orlando, Fl Lines: 42 This is a summary of responses received to my query regarding what part fails in the Macintosh power supply. Alas, the results weren't too conclusive, as yet. I received only two responses to the query (I guess that reflects the different user-demography of the people who buy Macintoshes, i.e., more software than hardware oriented). One person said that, in Macintoshes that are carried around a lot, a board or connector comes loose, "unloading" the power supply. (I assume this means that the power supply becomes disconnected from its load, which in certain designs of switching power supplies will indeed cause the power supply to fail.) He said that this causes a resistor to fuse open on the power supply board, and that replacing the resistor fixes the problem. A second person said that an electrolytic capacitor on the analog board shorted, causing the flyback transformer to burn out. However, he wasn't sure which capacitor it was that failed. So, the problem is narrowed down a little now... in at least some cases, there should be a visibly burnt resistor on the power supply board which can be replaced to correct the problem. The other case would be much harder to fix after-the-fact; if it was possible to identify which capacitor was failing, I suspect it could be replaced before the failure occurred. If anyone experiences such a failure and takes their Mac apart to see what went wrong, look at the electrolytic capacitors and see if you can see any that appear to have gotten hot, or look like they have a greasy substance dripping out, or have the rubber stopper in the end sticking out. This should give some clue. I'll look in mine if it develops the failure (which I expect will happen eventually). Thank you to "smh" at AT&T Murray Hill, and Bart Massey at Reed, for responding to my query. -- UUCP: Ofc: jer@peora.UUCP Home: jer@jerpc.CCC.UUCP CCC DNS: peora, pesnta US Mail: MS 795; CONCURRENT Computer Corp. SDC; (A Perkin-Elmer Company) 2486 Sand Lake Road, Orlando, FL 32809-7642 LOTD(2)=a "I didn't watch the Super Bowl."