Flaky IIci

[scott]

I finally found some free time to rebuild my old IIci... The plan is to install A/UX 2.0 - something I've been putting off since around January of 2005. Unfortunately, my IIci is not cooperating.

Everything was going fine on Monday morning... The IIci fired up with no issues, and confirmed my suspicions that the hard drive was dead. I replaced the drive, and created the installation media, then powered the IIci back on... Nothing happened. No chime. The power supply fan did not spin. The system behaved as though it was not plugged in.

I unplugged it, and held the power button in to bleed out the capacitors in the power supply, then plugged it back in. Still nothing. I removed the hard drive, floppy drive, keyboard, mouse, monitor, cache card, and network card... Nothing. Removed and reseated the power supply... Nothing worked.

Now, here's the real kicker... It worked fine the next morning.

If this was the end of the story, I probably would not have bothered posting it... The bugger did the same thing again today. It worked fine for a few hours, then flaked out again. I expect/hope it will fire up again tomorrow morning.

I have checked the board for leaking capacitors, and do not see any obvious signs... No brown sludge around the caps. However, the dust does seem to cluster around the caps. Has anyone else encountered a similar issue with a IIci / IIcx? Am I looking at a power supply issue, or a mainboard?

 

[MrMacPlus]

I don't own any mac IIs but I think that the dust could be collecting on some sludge. just clean off the caps. Please prove me wrong.

 

[equill]

You would both probably be better-off if TetrisMaster512 were right. A good wash so that the MLB can be inspected for corroded-through traces, followed by the replacement of malfunctioning caps, may give a more positive conclusion. Failing that, you could elect to tear apart the PSU (with due respect for its filter capacitors' remnant charge) and test/replace/augment the bias diode in the sawtooth oscillator, because that could be the cause of the 'it-works-after-removing-the-PSU-for-a-while' syndrome. But before you bung your trusty 4-lb. iron on the charcoal brazier, do search these forums using 'IIci', 'Delta', 'Astec' and 'TRKL' as your search terms. You will find much discussion and some external references of potential use.

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[scott]

On closer inspection, there is a "greasy discoloration" around some of the caps... I think a capacitor-replacement is in order. I have some experience in soldering, so I don't think it will be a serious problem. [] ]'>

 

[wally]

http://home.earthlink.net/~gamba2/images/macIIcisch.GIF is worth a look if you have not already seen it. Before any cap surgery you can measure if +5 continuous is coming from the infamous power supply zener diode Z1 and if the startup circuit depicted on the motherboard is commanding the power supply to start up. Caps C6, 12 and 13 of course have to be good, and additionally any cap leaking could cause faulty connections not shown or intended. The PS is tedious to disassemble but if need be the +5 continuous "TRKL" schematic is easy to manually reverse engineer working back from the connector green wire to pin 10.

 

[scott]

Oh cool! Thanks!