Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!uunet!ogicse!blake!milton!gordon From: gordon@milton.acs.washington.edu (Gordon Davisson) Newsgroups: comp.sys.mac.hardware Subject: Re: Power supply failure on 2.5 Meg Mac Plus Summary: It has nothing to do with the RAM Keywords: power supply, failure, RAM, Mac Message-ID: <2158@milton.acs.washington.edu> Date: 27 Feb 90 08:37:00 GMT References: <1244@m3.mfci.UUCP> Reply-To: gordon@milton.acs.washington.edu (Gordon Davisson) Organization: University of Washington, Seattle Lines: 43 In article <1244@m3.mfci.UUCP> siritzky@mfci.UUCP () writes: >This weekend my MacPlus got very sick. The symptom was that the >entire screen image was a thin vertical line down the center of the >screen. It booted fine, just no image. The machine was originally >at 512 which was upgraded to a Plus right after the Plus came out. >Last year I added 2Meg of RAM, to give me 2.5Meg. Okay, so here's the >thing: when I took it to my local Mac-Repair-Doctor I said >"I have a MacPlus with 2.5Meg RAM and ...", before I could >finish he said "Do you have a thin vertical line down the middle of the >screen?". How did he know? 'Cos he's seen a lot of them. He says that >the problem is with the power supply. So, is the extra memory a problem >for the power supply? Am I going to have this problem again with my new >power supply, say when I upgrade to 4 Meg soon? What is the solution? >(Please don't tell me to buy an SE or a II[ci], I'd love to but can't afford >one!) First, the problem has nothing to do with the memory. 1-Meg SIMMs don't use significant amounts of power (I've heard they tend to use less than the 256K SIMMs -- the technology is getting better *that* fast). Second, the problem is not in the power supply; it's in the video circuits. It's on the same board as the power supply, but that only matters if you're going to repair it by replacing the entire board (like Apple does). Fixing things this way tends to be unreasonably expensive; you're better off either fixing it yourself or finding someone who does component-level repair (if you can't find someone locally, send it me -- see my .sig). As for the problem: the most common cause of this symptom is a cracked solder joint on the top pin of the yoke connector (it's the 4-pin connector near the top front of the analog board, right under the foam pad that holds on the insulating sheet) (the analog board, by the way, is the one that sits vertically on the left side of the Macintosh, and holds the power supply and video circuits). It's also possible (but much less likely) that some other solder joint in that circuit (the horizontal deflection) has cracked. Check the connections to the components labeled C1, L2, and L3. It also could be that C1 has died (though this doesn't usually collapse the screen as completely as you describe). -- Gordon Davisson Westwind Computing (206) 632-8141 4518 University Way NE, Suite 313, Seattle WA 98105