At 15:30 -0400 08/04/2005, System6 wrote:
Date: Thu, 4 Aug 2005 06:34:58 -0700 (PDT) From: Mel <[EMAIL PROTECTED]>
This morning, when I hit the start button, the three lights above the three buttons (num lock, caps lock and scroll lock) and the green light at the lower right of the CPU came on simultaneously; the CPU emitted a very short chime but the CPU never came on nor did the monitor.
First, you'd probably have better luck with this question on Vintage Macs list, because it is a hardware question, not a System 6 question.
Second, there are two possibilities. You could have a failed power supply or a failed motherboard.
Power Supply: I don't remember the details, unfortunately, though some time with Deja News might pull up relevant posts, but there's a fairly common failure mode for the power supply which, IIRC, may cause this issue.
Logic Board: On these old logic boards the electrolytic capacitors leak and the leakage is corrosive. Pull the LB, examine it closely, holding it at various angles to the light and look for discolored areas (brownish) in the rear right corner. If you find some, clean it up with swabs and isopropyl (rubbing) alcohol. Examine the area carefully for pitted and corroded leads and solder. You may find connections that are eaten through. An ohmmeter (continuity meter) is handy for this examination.
Some folks have had luck simply cleaning the corrosive off, but for a good fix, you need to remove the old caps and replace them, preferably with tantalum caps which won't leak.
The surface mount electrolytic caps are the little round silver cans on teh board. There's about a dozen fat ones (~1/4") and a handful of thin ones (~1/8").
Marc Schrier's Clock Chipping Home Page has instructions on removing surface mount resistors using the two soldering pencil method and this is relevant to remving SM caps as well.
Replacement caps in tantalum or electrolytic are available at Digi-key and other places.
The unfortunate fact is that a huge number of these grand old machines are experiencing this type of failure. We're seeing a lot of the SE/30s with the same problem over on the Classic Mac list.
I had this failure in my IIci back in the mid-90s when a IIci was still worth close to $1000. I had to bypass a corroded via (a hole that takes a connection from front to back of circuit board) with a bit of wire wrap to fix mine.
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