IIci clicks and dies at power-up

[bigmessowires]

I just picked up a IIci system, my first acquisition in a while. According to the previous owner, it was working as of about two years ago. When I power it up now, there's a brief click from the area near the power button, which sounds like a normal power-on click. The power LED on the front also lights up. But after less than one second, everything goes dark again. No fans or disks or anything else ever spin up.

Bad power supply? Bad wiring? Where might you begin troubleshooting this one?

 

[Elfen]

Besides the obvious recapping that it is going to need, that sounds like a signal diode failure in the PSU to me.

See link: http://www.shobaffum.com/iici/trickle.pdf

 

[max1zzz]

Caps, recap the logicboard.

IIci's and IIcx's often do this, both my IIci and IIcx did this before a logicboard recap, after both of them are working perfectly

 

[bigmessowires]

How can you tell if it's a logic board failure, or a power supply failure? I assume power supplies have capacitors in them too, but I never hear about people recapping them.

 

[techknight]

power supplies are recapped all the time. LC being the worst. 

 

[olePigeon]

You should just recap it no matter what.  While you're at it, you might want to just replace the power supply with a mini ATX.  Even after I recapped my IIci's power supply, it couldn't run a fully populated Radius Rocket.

 

[Elfen]

Though I agree with the cry to recap, especially on a machine over 20 years old, I would have to say to take a step back a bit.

Yes, recap the mother board, that is needed and may improve things for the PSU. But check if the PSU is working first. That link I sent says how to check for the trickle charge for the machine to turn on when you press the power button. If that trickle charge is not there, fixing it with a couple of diodes. Then replace the caps of the PSU if that fails.

Recapping the PSU will be needed eventually. Like Techknight said, PSUs are recapped all the time - the LC PSUs needing it the most. The job is not that hard. I've recapped a couple LC PSUs myself. But lets make sure that the PSU is working first. From the sounds of it, the clicking of the relay inside, it does. Check for that trickle charge first.

 

[olePigeon]

This is BMOW.  I think he knows how to solder.

 

[unity]

I agree on the mobo recap - I had no spare power supply to use and recapped it, same issue. Sent my board to uni, works every time. I ended up putting most of the original caps back in the power supply (prototype machine).

 

[bigmessowires]

Thanks everybody. I was eventually able to get the machine to boot, after removing the dead PRAM battery, and wiping away capacitor goo with a pencil eraser. But it's still got problems.

It boots fine from the keyboard's power button, but the power switch at the back of the machine still only does clicky-clicky when pressed. If I hold the power switch in, the machine will boot and run, but I have to keep my finger holding the power switch in the whole time. As soon as I release the switch, it shuts off.

No sound at all from the built-in speaker. 

I'm assuming since it boots and runs okay from the keyboard power button, that means the PSU is ok? And it just needs a motherboard recap like everybody's saying? I've never done one before, so I guess I'm dragging my feet looking for other explanations.

 

[unity]

Sounds about right for a mobo recap. You could try washing it to see if it improves more. Washing will get more of that conductive good out from under the caps. And if you recap, its best to wash before anyway.

 

[Elfen]

Is there a Mac IIci Schematics? Sounds like some traces going bad on the Power Button, and bad caps on the area. Washing the board should help greatly as the cap goo can be conductive.

 

[bigmessowires]

I'll give that a try. Do you just put the board in the dishwasher? With or without soap? Sani-rinse cycle? My wife is going to love this.

 

[bigmessowires]

Found this schematic of the IIci startup circuit. http://home.earthlink.net/~gamba2/images/macIIcisch.GIF

 

[Elfen]

I wash my boards by hand, personally. A a 1/2 full plastic bucket, bit of dish soap, some alcohol and acetone with a tooth brush. Direct toothbrush and pure acetone on rough spots. And then rinse out with distilled water and alcohol.

 

[Elfen]

That schematic is great! I'm eyeing capacitors C11, C12, and C13 as a starting point. C10, C14, C17 would be next and lastly C6 and C26 - all in that circuit. Also check the traces from UD13 and UE14 to the power switch.

 

[bigmessowires]

Yeah, I'm thinking that because it boots OK with the keyboard power button, but not with the rear power switch, that's a strong clue it's a capacitor problem. I see the keyboard power button directly grounds the junction left of R43, but rear switch grounds it through C6. And then it'll only stay grounded for a brief time, whose duration depends on the values of C6 and maybe C12 and C13. Keyboard power button also doesn't touch the power-off circuit (that whole section at lower center), but the rear switch does, so I suppose anything in that section could be bad too, including the caps or any of the ICs. 

Once booted, the Finder's shutdown command works OK, so I'm guessing that power-off circuit is fine. So my bet would be on one of the three caps in the power-on circuit, most likely C6. If its capacitance has fallen to significantly less than its rated value, I think that would produce exactly the behavior I'm seeing. It would charge to 5V too quickly, bringing the R43 junction high again before the PSU bootstrap through D6 could be established. So it would just click on and immediately off again. Although now that I think about it, that wouldn't explain why pressing *and holding* the rear power switch works. Oh well.

Anyway, recapping, here we go! Fun and excitement will now commence.

 

[olePigeon]

Don't forget you can get your caps at Excess Solutions.  They've moved:  1555 S 7th Street, San Jose.

 

[Elfen]

Looking at the schematics one more time, C6 is 47µf, and I can bet it is probably that dreaded 47µf @ 16V that leaks on all the machines that has it. Chop it's little head off and replace it with a Tantalum SMD.SMT one. I'm beginning to hate that one cap!

*looks at his board to verify it*

(IT IS!!!)