Macintosh IIci strange power on behaivor

[nubus_bagel]

So, I recapped and cleaned up my IIci a while back now, probably just under a year ago now. It's largely worked fine since, but there have been some strange things it has done, with one of them being an inconsistent power on. If you plug it in after sitting around a minute or longer, it'll automatically power on after about 5-15 seconds. The time isn't consistent, and trying to use the power button does nothing before it boots. After it's plugged in, if it sits off for a while (more than a day, typically), and you use the ADB keyboard to power it on, it behaves similarly, taking a few seconds to react. I believe the rear button doesn't have that issue, but I rarely use it, so I haven't tested it that way lately. Is there anything I should check, or is this actually more or less normal and just not really brought up because of it? Thanks!

 

[jmacz]

Certainly not normal… but very common. Leaking capacitors C10 through C13 cause damage to the IIci’s soft power circuit by damaging nearby traces and chips UB13, UD13, UE13. Even if you have recapped those, there could be remaining damage to the traces/chips, or there could also be cap juice remaining under those three chips causing power on issues. Otherwise it could also be your PSU if you haven’t recapped it. If you search for IIci and soft power both on this board and on the internet, you should be able to get ideas on what to look at. Very fixable but you will have to do some debugging.

 

[speakers]

Yep. In my case, a similar problem showed up after recapping and persisted after replacement of UE13. Removal of caps C10..C13 again, more cleaning with IPA and application of additional solder mask did the trick though. There's a collection of RC timer circuits sensitve to lingering cap juice leakage.