IIci won’t stay on

[derFunkenstein]

I got a IIci about a week ago. Supposedly the power supply had been recapped. It was working perfectly until today when I tried to turn it on. Today it just flickers and dies. Here’s a video. Anyone with ideas I’d love to know!

I should say I have unplugged everything and replaced the PRAM battery but not much else. I’m just scratching my head.

 

[finkmac]

check the power circuit, check the power supply.

 

[derFunkenstein]

What am I checking on the power supply?

 

[David Cook]

There are two common reasons why it might be doing this:

1. A short. The power supply protects the board if too much current is being drawn. For example, if a tantalum capacitor has gone bad and is shorting the +5V and GND. With power off and a multimeter, check the SCSI power connector pins across 5V/GND and then 12V/GND to see if the resistance is too low.

2. Damage to the power circuit on the IIci board. This is very very common. Capacitor juice either erodes a trace or damages the off-the-shelf logic chips. Here are my repair instructions: (someone commented that if you're going to replace the chips anyway -- which is a good idea -- then you can carefully clip them out rather than desoldering)

https://68kmla.org/bb/index.php?threads/macintosh-iici-no-chime-and-blackscreen.46679/#post-522499

- David

 

[derFunkenstein]

Hi David thanks for the detailed reply. Attached here are some images up close of the area you mentioned. It all looks very clean and proper to me. Do you see anything that stands out as a potential issue? From your other post it seems like there might not be anything visible.

 

[Chuckdubuque]

Has the logic board been recapped and cleaned?

 

[derFunkenstein]

Has the logic board been recapped and cleaned?

That's what the seller told me, and from the photos I feel like it looks awfully clean. Clean to the touch as well.

Also in the photos I saw something looking like a tiny piece of metal bridging a couple pins on UE13. It was just a rogue dust. I wiped it away with my finger and no change.

 

[techstep]

I could be wrong but it doesn't look like the logic board capacitors have been replaced. There also appears to be some corrosion around C12,C13, D6, etc.

 

[derFunkenstein]

If that's the case I'm going to be super annoyed. I've only just started getting into recapping work myself and have been practicing but I'm not very good yet.

 

[Chuckdubuque]

It's hard to tell from the photos, but any sign of green (cap juice corrosion) or dust you cannot blow away with canned air (which is therefore stuck on with cap juice) is a sign of bad caps. It can be subtle or quite spectacular--you may have a more subtle variety...

 

[Byrd]

Also, simple check but make sure the power switch on the back latches down and isn’t faulty

 

[David Cook]

Also, simple check but make sure the power switch on the back latches down and isn’t faulty

Good point. The power supply switch rotates in place. So, it is worth playing with a bit.

That being said, the IIci board is definitely not recapped and there is corrosion. However, it doesn't look awful. So, the board is likely an easy job.

 

[derFunkenstein]

At the same time as I posted this thread, I also sent an inquiry to Thomas at Amiga of Rochester, and he said the same thing. This board has never been touched. I popped the fan off the power supply to see that it's never been messed with either. I don't like that it was apparently misrepresented to me but it's too late to do anything about it now.

Thomas called me and we talked for 30 minutes or so, and he was pretty certain it'd never been touched despite what I was told when I bought it. That's very frustrating and I'll be sure to let the seller know that you all identified the lack of attention to this thing from the get-go. I'm going to send the motherboard and power supply to him to repair. He was so generous with his time that the least I can do is compensate him for his services.

Meanwhile I'll be buying dead Macs and trying my hand at recapping stuff myself. If I can start fixing this stuff on my own, I won't have to bug you all.