Mac IIci rebooting over and over automatically

[reallyrandy]

I have a Mac IIci that was having sound issues (really quiet, could hardly hear it) so I recapped it last night (while watching Mac84's live cast). Today I put it back together with only four 1 MB chips in bank A and left out the cache card and battery and left the top off the case.
I hooked it up to a 13" RGB Apple monitor drawing power from the wall (not from the IIci) and it chimed and booted perfectly. I tested the sound and it worked fine.
After about 30 minutes, it started rebooting over and over every 5 seconds or so. I unplugged it and re-plugged it in and hit the start button and it did the same thing. I have not recapped the PSU yet but it was fine a few weeks ago.
Any ideas what I should be checking?

 

[reallyrandy]

I let it sit for 10 minutes and it started up fine, this time after about 5 minutes it started rebooting over and over.

 

[pfuentes69]

I have a Mac IIci that was having sound issues (really quiet, could hardly hear it) so I recapped it last night (while watching Mac84's live cast). Today I put it back together with only four 1 MB chips in bank A and left out the cache card and battery and left the top off the case.
I hooked it up to a 13" RGB Apple monitor drawing power from the wall (not from the IIci) and it chimed and booted perfectly. I tested the sound and it worked fine.
After about 30 minutes, it started rebooting over and over every 5 seconds or so. I unplugged it and re-plugged it in and hit the start button and it did the same thing. I have not recapped the PSU yet but it was fine a few weeks ago.
Any ideas what I should be checking?

I suggest you start by the PSU. It’s very likely you need to recap it too.

 

[reallyrandy]

I plan on recapping the PSU at some point, but I don't want to just blindly recap it without knowing this is a PSU issue and not a logic board issue. Recapping a IIci PSU is a HUGE pain.

 

[pfuentes69]

I plan on recapping the PSU at some point, but I don't want to just blindly recap it without knowing this is a PSU issue and not a logic board issue. Recapping a IIci PSU is a HUGE pain.

Yep. I had to do mine and it’s a pain… but it was needed… in my case one of the RIFA caps exploded and I had a funny smell in my room for many days… when I opened it I could clearly see cap juice in several places.

I guess you can only be sure if someone could lend you a PSU to test…

Did you try without the HD and floppy connected?

 

[reallyrandy]

The floppy isn't connected but I do have a 250MB spinner connected. What puzzles me is that it ran for 3 or 4 minutes so I know it's not a short. It didn't have a chance to heat up so I know it's not a heat or a heat related expansion problem.
If there's anyone in New Jersey with a IIci PSU that wants to help test this with a known working one, I'm all about it.

 

[reallyrandy]

I am noticing the less time I let it sit, the sooner it starts the auto-rebooting. If I let it sit for 15 or 20 minutes I can boot it and start up techtool and read through the specs. If I only let it sit for 2 or 3 minutes, I can't even get through the boot cycle before it reboots.

 

[Volvo242GT]

Does the machine work normally with the power supply from one of your other IIci machines? If so, then yes, definitely power supply related.

I mentioned in a PM to @olePigeon over at the other forums, that I'm planning to upgrade my IIci to a power supply from a Centris 650... A little heavier duty, due to the need to power both a hard drive and a CD-ROM drive... That, plus a little newer, since they were used through 1995 in the 7100 series PowerMacs. Guess he wants a power supply for his IIci.

 

[reallyrandy]

Unfortunately, I don't have the other 2 any longer (I forgot to take them off my signature). That's the first thing I woulda tried. I looked on Console5 but they only have a cap kit for the GE PSU.

 

[Volvo242GT]

Unfortunately, I don't have the other 2 any longer (I forgot to take them off my signature). That's the first thing I woulda tried. I looked on Console5 but they only have a cap kit for the GE PSU.

Ah, ok. PM'ed you.

 

[reallyrandy]

I bought a "new" PSU from Herb at retrocomputing and it seems to have solved the problem. Thanks @Volvo242GT

I'm working with Console5 to put together a recap kit for the Astec PSU for the Mac IIcx/IIci.

 

[reallyrandy]

I spoke too soon. after 19 minutes of running it went back into the reboot cycle booting over and over.

I noticed there was a wonky via on the negative side of C14. I desoldered it and cleaned it up until I could see the metal pipe that makes up the via. I'm getting continuity between the negative and positive via on C14. Is that normal? If not, why does it run for a while until it's warm and then start rebooting? The negative side just goes down into the board and I can't see any traces coming from it.

I'm gonna go get a another 470µF 16v cap and replace the one that's there but I don't think that'll fix it. I have no idea what do or what to look for at this point.

In the pics you can see where I'm referencing. The gunky looking stuff is solder mask.

 

[pfuentes69]

These Macs that have part of the power control in the logic board (to allow powering up with the keyboard and software shutdown). I'd check that part of the circuit first maybe. I had some issues with that on a IIsi.
In particular, this zone maybe:

Just in case, I added the schematics in the resource section.
Good luck!

 

[reallyrandy]

Thanks, Now if I only knew how to read schematics!

I think the most puzzling part is that it works before it gets warm.

 

[pfuentes69]

Thanks, Now if I only knew how to read schematics!

I think the most puzzling part is that it works before it gets warm.

You can just focus in the first page as the power circuit is there. You should easily identify the ICs such UB14, UE13, UD13, and the caps and other components in that area. If the traces are fine, it could be that the cap juice is affecting UE13 and UD13 (I’m mostly guessing!).

 

[reallyrandy]

I reflowed the solder on UB13, UD13, and UE13 and started checking continuity. In the attached pic on UE13, I have no continuity between points A and B or points A and C. Does this trace look broken to you? Is there supposed to be continuity here? I looked at the schematics but I have no idea what I'm looking at. It doesn't look any different than the first leg or the 5th leg.

 

[reallyrandy]

Same as this leg on UD13. I looks squared off, like it's supposed to be that way.

 

[rikerjoe]

I reflowed the solder on UB13, UD13, and UE13 and started checking continuity. In the attached pic on UE13, I have no continuity between points A and B or points A and C. Does this trace look broken to you? Is there supposed to be continuity here? I looked at the schematics but I have no idea what I'm looking at. It doesn't look any different than the first leg or the 5th leg.

View attachment 3806

View attachment 3808

To my eye it looks like the pad at point A does not connect to the trace going to point B, based on the black gap between the pad and the trace. I had several similar instances on an SE/30 which I repaired by scraping the trace adjacent to the pad and either bridging via solder or adding a wire to make continuity. Does B to C give you continuity?

 

[reallyrandy]

B to C does give a continuity beep. What puzzles me is the IIci runs fine for about 10 minutes before it starts the rebooting loop.

I have another instance of this on my SE/30 that I'm repairing as well.

I'm guessing in ALL instances of a trace coming up to a pad there should be a connection? Is there any instance where it looks like the trace belongs to a pad but is NOT supposed to be connected?

If that's the case I can run a solder bridge between all the pads and traces that aren't registering continuity on the IIci and the SE/30.

 

[pfuentes69]

If you check the schematics...

You can see that Pin 2 of UE13, goes to the positive side of C12, and to the resistors R44 and R43, that most likely are in the backside of the PCB and are connected to the pad you marked as "B", so, maybe this can help you to interpret the connections, but in general, if you see a trace that goes to a pin then you should always get connectivity between all ends of that trace, and if you don't, something needs to be fixed.

Heat can make things that work marginally to stop working. It could be a trace that has a very faint connectivity, it could be some cap goo under a chip that makes things go worse when it's hot...