IIci restarts after shutdown

[KhanTyranitar]

So I'm far from an expert and new here on the forums. I just successfully recapped and repaired a IIci. However when it's plugged in it powers on by itself and when you shut it down it powers back on. Not the worst problem, but I would like to fix it but I don't know what the cause is and I haven't been able to find a solution online.

Just so it's clear I have tried the switch on the back in both positions and it makes no difference.

 

[MJ313]

I had this exact problem with my IIcx and after testing different power supplies, checking caps, rewashing the board etc., it turned out to be the keyboard of all things. Easy enough to check if you have a spare keyboard. For some reason the soft power switch in mine got fouled. 

 

[KhanTyranitar]

Nope not keyboard. I do have two keyboards. It does this whether or not the keyboard is even plugged in and it makes no difference which keyboard is used.

 

[Bolle]

One of the 74s logic ICs at UB13, UD13 and/or UE13 on the IIci logic board (UK2, UL2, UM2 on IIcx boards) are broken due to cap goo leaking into them. Those belong to the startup circuit and when defective result in weird power on/power off/restart behaviour.

Replacing the chips usually fixes any weird behaviour.

 

[KhanTyranitar]

Ok. I'll go ahead and replace them. I'll let you know how it goes.

 

[Bolle]

The schematics for the startup circuit of both machines are available here by the way: http://home.earthlink.net/~gamba2/schematics.html

Just in case replacing/testing the chips does not solve it. I had a IIci board once that had a few broken traces in addition to a broken 74hc132 in the power circuit.

It did also power itself on as soon as power was supplied until the two traces had been fixed.

 

[KhanTyranitar]

Oh. Thank you. I'll change out those chips tonight.

The schematic is perfect for checking continuity. I'll see if the traces are good.

 

[trag]

Check to make sure the power button (rear bottom corner of case) isn't in the locked-in position first...

 

[KhanTyranitar]

Check to make sure the power button (rear bottom corner of case) isn't in the locked-in position first...

Already mentioned in my original post.

 

[Scott Baret]

Glad to know I'm not the only one with a re-capped IIci who has this problem.

Does your IIci also power up on its own whenever it gets plugged in?

My simple solution was to use a power strip.

 

[Compgeke]

My IIcx also suffers this issue and I traced it down to being a problem with the 74 series chips under the floppy drive. I ended up giving up, not wanting to deal with SMT IC replacement. 

Another thing worth checking is whether your PSU has 5VSB or not. Without 5VSB, /pfw will never go high and as such never tell the PSU to turn off, providing it'd turn on in the first place.

 

[KhanTyranitar]

Ok. I didn’t have a chance to delve into it too deeply last night. But it’s good to know about other suspect areas.

The PS is not the issue, I have three good power supplies, it always does the same thing. I’m hoping to have time tonight.

 

[KhanTyranitar]

Ok. I fixed that issue. The 132 did have a pin that was not making contact with the board. Rather than mess with it I just desoldered and replaced it.

 

[KhanTyranitar]

As an added note, the clock wasn’t working. As in settings were being retained, but time wasn’t passing. So I desoldered the RTC chip and put in another from another board I have. That fixed that issue. Guess the battery that blew up and leaked ruined the RTC chip.

The unit seems to be 100% working now.

 

[trag]

Already mentioned in my original post.

Apologies.  I did not read as carefully as I should have.   I thought I did...

 

[Bolle]

Common issue when the RTC chip dies. It usually sits close to the battery and is prone for being killed by leaking batteries.

Good to see that one being 100% up and running again.

 

[KhanTyranitar]

For me this was an interesting project. I had a IIcx growing up. So I bought a IIci. It wouldn’t start. So I recapped it, still didn’t start. Replaced both HC132 chips, still nothing. It had what I would call, serious damage from multiple cap leaks. I then found some of the vias that tie to the power or ground planes were basically gone and that the juice had gotten down between the board layers.

So then I got another logic board on the surface it looked much better. Wouldn’t power on either. So I recapped it. Now it would power up, would even chime, but it was hanging up. It had no video, no disk activity. I checked the ROM traces, couldn’t find anything wrong. It just would not work. So I found yet another IIci that was supposedly working last time it was used, but had no hard drive. So I bought it, it powered on as soon as you plugged it in but had no chime. So I opened it open and the battery had exploded and done a lot of damage. But after repairing the damaged traces, it gave me a chime and video and tried to boot. So then I recapped it you guys know the rest. The worst looking of the boards was the only one I was able to get working. But it works completely.

 

[Scott Baret]

Should toss in a random IIcx story while I'm at it...

Back in 2004-2005, I was refurbishing an entire closet of older Macs from a school to prepare them for donation. Among the lot was a IIcx. I plugged it in, dead on arrival. Figuring I'd take care of some of the other machines before looking at it closer, I just kept it plugged in and went to work on a few Power Mac 5xxx computers.

About an hour later, I had become so intent on getting through a pallet of 5xxxs that I had forgotten all about the IIcx. Suddenly, out of nowhere, I heard its startup chime. This was entirely on its own...no keyboard key or back button was pressed.

It sounds like it had the same problems as these computers.