Date: Wed, 7 Jan 2004 00:09:13 +0000 (UTC) From: Terence Dennis Sherman <[EMAIL PROTECTED]>
Well, I replaced the PS, and still, it shuts itself off after a while. Unless I have had two power supplies go bad in the same way, it would seem that the trouble lays elsewhere. I shall try the mobo next. A good cleaning seems to be in order.
Despite someone's earlier somewhat scoffing comment on the topic, the problem in these cases really does lie with the motherboard most times. The root cause is that the surface mount electrolytic capacitors leak after many years. They leak corrosive. The corrosive sits on your motherboard and eats the solder and the traces and eventually things (like the sound and power up circuitry) stop working.
The capacitors in question are little silver cans about 1/4" in diameter. They look like tiny gasoline storage tanks (the big ones in tank farms) scattered about the board, but concentrated in the rear right corner. There are some smaller ones as well.
They need to be replaced, as they may continue to leak and add new corrosive to the board after you've cleaned it. Also, a close examination of the board may reveal the corroded solder joint or trace which has undone your sound.
If you aren't interested in soldering, then a new IIci board from Ebay is a better bet and likely about as cheap, but any board will develop or already has developed this same problem. It's also a problem on the SE/30 boards and we discuss it regularly on the Compact Macs list.
The old capacitors are simple to remove. It requires two soldering pencils. If you do not have them, Radio Shack has a nice 15 watt model with a three pronged plug for under $10. A pair of those will do nicely.
Allow the pencils to heat. Then apply one to each side of a capacitor where it is soldered to a pad on the board. Wait until the capacitor comes loose on its own. Don't lift it forcefully as you might pull the pad off of the circuit board. Also, don't grind the pencil into the board. There's a tendency to do the latter, if one feels that the pencil isn't making good contact and heating the work properly.
Replacement caps are available from Digi-Key and other places (probably Mouser). Digi-Key isn't so great a choice for this kind of thing because they have a $25 minimum or they charge a $5 surcharge and the needed caps cost about $3 or $4 total.
Gamba, on the Compact Macs list has been recommending that folks replace these caps with SM Tantalum capacitors. The tantalum caps will not leak corrosive onto the board so they are a more permanent fix rather than a six to ten year fix. They are more expensive costing about $.50 each or thereabouts rather than $.15 - .$20 each.
To solder a replacement in place, first clean the pads. Do this by using some desolder braid (also available at Radio Shack, but I prefer the Chemtronics brand Chemwick available from Digi-key or Mouser) to remove the solder on the pads. Then clean the pads and surrounding area with isopropyl alcohol and a swab or spray it with a flux remover. Then tin one pad by melting just a bit of solder onto it. Then place the capacitor in place, melt the solder on the one pad with a soldering pencil, and push the end of the capacitor into place on the pad. The pushing is usually easiest done with a small short screwdriver or similar implement--tweezers work well too.
Once you have one end of the capacitor soldered into place, it is simple to solder the other end.
If I was doing an entire board, I'd inspect the board for discolored areas which might lead me to damage caused by corrosion. Then I'd remove all the electrolytic caps. Then clean the entire board with a flux remover (Frys has Flux Off for $5.99 a can) or other spray solvent, then repair any corroded or damaged solder joints or traces, and then install the new capacitors.
I'd offer to do this for folks for a nominal fee, but shipping the board both ways would make it not very worth it.
Back around '94 or '95 a company was doing this for folks for about $100, but that was back when a IIci was still worth about $1000. They advertised in the news groups (usenet).
Jeff Walther
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