Path: news1.icaen!news.uiowa.edu!iagnet.net!207.22.81.9!europa.clark.net!206.229.87.25!news-peer.sprintlink.net!news-sea-19.sprintlink.net!news-in-west.sprintlink.net!news.sprintlink.net!Sprint!151.164.1.34!swbell!not-for-mail From: Rubywand Newsgroups: comp.sys.apple2 Subject: Re: GS Power Supply: Warning signal? Date: Mon, 29 Sep 1997 21:20:50 +0000 Organization: Southwestern Bell Internet Services, Richardson, TX Lines: 54 Message-ID: <34301BB2.2415@swbell.net> References: <60oiq6$rjk@login.freenet.columbus.oh.us> NNTP-Posting-Host: ppp-207-193-12-19.hstntx.swbell.net Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Trace: nnrp1.rcsntx.swbell.net 875589387 27199 (None) 207.193.12.19 X-Complaints-To: usenet@nnrp1.rcsntx.swbell.net X-Mailer: Mozilla 2.02E (Win16; I) Dave Althoff writes ... > > Just wanted to relate my experience with GS power supply failures on > upgraded ROM 00 GSes. My GS at work is a ROM 00 upgraded to a ROM 01. It > is now on its third power supply > > .... > Anyway, I have noticed what seems to be a warning signal when the power > supply is about to die. .... > > It seems that when the power supply is about to go, the crackling becomes > more frequent and more pronounced. .... Then, when I returned a bit later, > the supply was dead. In fact, I cracked the thing open and there is this > nice crunchy ceramic cap, and a couple of clearly overheated spots on the > board. > > .... I thought I would pass that along in case there are GS > users out there watching for telltale signs of power supply failure... > Thanks for the info. Your GS seems to be eating power supplies. Ours is a Woz ROM-00 machine (one of the first three purchased in Houston) which went through the ROM-01 upgrade and a few motherboard swaps. It is still on the original (no internal fan) power supply, except that, before adding a Zip-GSx accelerator, 4MB RAM, etc., we fattened-up the PS leads. If there is something odd about the line voltage at your workplace-- like it is too low or too high and/or you get frequent surges-- you may want to get an UPS. Otherwise, the thin leads on your power supply could be contributing to instability, over-currents, and failure. You mention finding a "nice crunchy ceramic cap". Are you sure it was a cap? A common failure point on Apple II supplies is a capacitor-looking thing called a "globar". It is a disc-shaped resistance element which is in series with the AC line input. When power is turned ON, the globar is cold and has a resistance of, very roughly, 50 Ohms. A second or so after turn-ON, it has heated up and its resistance drops to just a few Ohms. The idea is to limit initial surge voltages. A globar can fail quickly-- a lead pops off or the element cracks and separates; either way, the AC input line is broken and everything stops cold. Or, a globar may fail slowly-- a lead connection fractures or the element develops cracks but does not separate. A slow-failing globar could produce the audio noise you mention. Anyway, try beefing-up the +5V, +12V, and one GND lead to #10 or #12 gauge. This may help save your present power supply. Rubywand