Macintosh IIci with leaky caps

[Dennis Nedry]

I have 2 Mac IIci s. One turns on fine but has no startup chime, display, or function. Does not access hard drive. It doesn't respond to power button to turn on or off and it comes on automatically a couple seconds after being plugged in. This Mac was stored outside in harsh conditions for a while, a little wet with extreme heat and extreme cold (-20 to 100+ degrees F) so it may have all sorts of problems. Amazingly, the plastic didn't turn particularly yellow. It was extremely dirty but cleaned up to like-new cosmetic condition. Also there was a somewhat rusty ImageWriter II out there that, OF COURSE, still works perfectly and even has a good ribbon.

The other IIci works fine but sound is nearly inaudible. Audio output is fine and the internal speaker itself is fine. Speaker is indeed mute when audio output has a plug in it. Capacitors have leaked on the motherboard. I cleaned this up, but I can only assume the capacitors are the culprit and should be replaced before they leak more.

Does anybody have experience replacing the caps in a IIci? I heard someone recommending using tantalum caps. Does anybody have any suggestions for the really screwed up IIci? Would it be wise / worthwhile to try replacing the caps on both motherboards? I imagine the extreme freezing and heat would be particularly hard on liquid-filled caps. This Macintosh was stored outside for at least 4 years.

 

[JRL]

trag does. He replaced the caps in his Macintosh IIci and is selling caps for the IIci and SE/30.

 

[Dennis Nedry]

Wow, there it was right in front of me. That's good to see someone's selling them right here.

I guess my 2 remaining questions are:

How likely is this to fix the sound issue on the working IIci?

How likely will this fix the non-working IIci; is it really worth trying on that one?

 

[Dennis Nedry]

I happened to have 4 of the SMD 47uF caps so I replaced several of them. The sound problem was caused by either C2, C3 or both. It's probably about time I replace them all, though, since they're leaking all over the place! C2 and C3 appeared to NOT have leaked, though, so I guess it's good to just replace them all at once.

I replaced with identical electrolytics except with higher voltage rating.

 

[equill]

Close inspection of the hardy outdoor IIci is warranted, because temperature cycling can induce cracks even in malleable metal such as solder. Then there is the effect of freeze-thaw cycling in caps with aqueous electrolyte. However, it may prove to be the large axial caps under the PSU, filter/smoothing caps in the PSU, and vertical aluminium electrolytics (as you found in the sound circuits) on the MLB that need most attention. Best of luck in your mission.

de

 

[Dennis Nedry]

Thanks for the info. I believe that the power supply is good but I can test for sure by swapping into the good IIci. The motherboard is cosmetically in very good condition, but in all likelihood it's damaged to such an extent that it won't be worth even trying. I imagine that such cracks as you have mentioned could be so small that they would be invisible to the naked eye.

I don't have that particular machine with me at the moment, but I'll try replacing caps and see what difference that makes. If that doesn't work, I may need to consider finding a new logic board, or just leave it because it's an attractive machine even when not running.

 

[equill]

The IIcx, IIci and Quadra 700 have a common PSU. They therefore have faults in common. 'Soft power' (active power control) on from the keyboard switch requires the presence of a 5V TRKL ('trickle') supply in the PSU. Soft power off needs that the TRKL voltage fall to <1V when Shut Down is invoked from the Menu or the keyboard. Auto-start/restart rests with the adjustable rear switch. In how many ways can all of this go wrong? You are just now discovering the answer to that question.

TRKL is probably the commonest villain, especially with Astec PSUs. Do a search in these forums for 'Astec' and 'IIci', and 'Delta' and 'IIci' to get the gen. Sheeting home the blame to the PSU, however, relies on the assurance that the MLB is good, so make sure of that first.

de