cander@unisoft.UUCP (Charles Anderson) (12/02/89)
I came home from dinner the other night to find my Mac II running. My
immediate conclusion was that I had left it on for a few days since the
last time I had used it. So I shut it down from the Finder menu only
to have it restart as soon as the power went off. So I yanked the ADB
cord out of the extended keyboard and shut it down again. This time it
stayed down.
My first idea was that it was related to the high humidiy we had with
the rain on that day. My hypothesis was that there was a bunch of
moisture shorting the power key in the keyboard. Since then it's been
very dry, but the Mac continues to restart itself, usually taking a few
minutes or an hour before restarting.
Does anyone have any ideas on how to exocise this evil presence from my
system?
--
Charles.
{sun, ucbvax, pyramid, uunet}!unisoft!canderdplatt@coherent.com (Dave Platt) (12/03/89)
In article <2670@unisoft.UUCP> cander@unisoft.UUCP (Charles Anderson) writes: > I came home from dinner the other night to find my Mac II running. My > immediate conclusion was that I had left it on for a few days since the > last time I had used it. So I shut it down from the Finder menu only > to have it restart as soon as the power went off. So I yanked the ADB > cord out of the extended keyboard and shut it down again. This time it > stayed down. > > My first idea was that it was related to the high humidiy we had with > the rain on that day. My hypothesis was that there was a bunch of > moisture shorting the power key in the keyboard. Since then it's been > very dry, but the Mac continues to restart itself, usually taking a few > minutes or an hour before restarting. > > Does anyone have any ideas on how to exocise this evil presence from my > system? I had this same problem... although the guilty device was a Kensington Turbo Trackball. Your conclusion about humidity is correct... it takes very little current-leakage across the PC-board traces to trigger the "Power on!" detector in the Mac II. Apparently the power-on circuit in the keyboard is designed to draw very little current... thus ensuring that the lithium battery in the Mac II isn't run down too quickly. I fixed my trackball by drying it out in the sun, opening it up, noting where the power-on trace ran across the PC board (it went from the in-port to the out-port, and wasn't connected to any circuitry in the trackball), figuring out where the short-circuit was occurring (pressing my finger firmly to the traces was enough to make the Mac boot!), and insulating the traces with a dab of fingernail polish. The problem went away and has not recurred. If you prefer a slightly more high-tech solution than fingernail polish, you could probably buy a can of silicone- or urethane-based "conformal coating"... an aerosol spray designed specifically for sealing PC boards and components against moisture and contamination. With fingernail polish, you should try to moisture-seal the PC-board solder contacts of the power-on switch, the contacts for the ADB connectors, and the PC-board trace which handles the power-on signal. With an aerosol conformal coating, you could probably spray the whole solder-side of the PC board (enough to coat, not enough to drip and run). -- Dave Platt VOICE: (415) 493-8805 UUCP: ...!{ames,apple,uunet}!coherent!dplatt DOMAIN: dplatt@coherent.com INTERNET: coherent!dplatt@ames.arpa, ...@uunet.uu.net USNAIL: Coherent Thought Inc. 3350 West Bayshore #205 Palo Alto CA 94303