IIcx Power Woes

[mcdermd]

So, I've been doing rounds with this Iicx I've got. I know there are a ton of tips on IIcis with capacitor and Astec power supply problems but this IIcx has been fully recapped and has a GE power supply. I've opened the power supply and don't see any physical damage to any components. The old capacitors didn't appear to do any damage to the logic board when they leaked.

When I plug it in, there's no sign of life. No clicks, pops, blinks — nothing. If I leave it plugged in for 15 minutes or so, it will start on it's own. When I select Shut Down, it will complete the shut down, then immediately restart. It has the exact same behavior when I plug in the power supply from my PM 7100. This seems in line with the problems I read about with IIcis and Astec power supplies.

Ideas?

 

[Trash80toHP_Mini]

WAGs:

When you say "turn it on," how are you doing so, power strip KBD or power switch on the back?

From the behavior, it says "mechanical" to me, Soft Power circuit/thermal expansion related.

Swap the KBDs and see if the problem moves?

Check the MoBo for a cold solder joint gone bad on the connector or soft power circuitry?

 

[mcdermd]

I'm attempting power on from both the keyboard and the physical switch in the back.

I can look for cold joints but I am doubtful it would be the cause. Once it has been plugged in a while and started up, it acts like the button is always on. It is pretty much the same as if the power button was in the locked position.

 

[volvo242gt]

PRAM battery's good, right? That is a weird one, for sure.

-J

 

[CC_333]

Once it has been plugged in a while and started up, it acts like the button is always on. It is pretty much the same as if the power button was in the locked position.

Maybe the switch is bad?
I am not very educated in these matters, but perhaps you can remove the switch and see what happens.

c

 

[onlyonemac]

I'm thinking, in line with Trash80toHP_Mini, that it could be a cracked track. I'm thinking of a connection around the power button connection that's open when it's cold, but then warms up and then closes, staying closed permenantly.

 

[James1095]

Did you re-cap the power supply too? The Aztecs may be harder on the capacitors, but the other brands aren't immune to trouble. Capacitor failure in switchmode power supplies is extremely common, and ESR typically drops as the caps warm up. It's the usual cause of equipment that's cranky when cold but improves gradually as it warms up.

 

[Macdrone]

I'm watching this thread closely as the one I got turns on but doesn't chime and stays on.

 

[dougg3]

Since you've tried a (known working?) 7100 power supply and it does the same thing, I doubt the power supply is the problem. I would have to guess something is messed up in the power circuitry on the logic board. Here's a schematic from Gamba's site--



Unfortunately trying to read a schematic like that is complete gobbledygook to me--maybe someone with more electronics knowledge might have an idea of where to look...

If you still want to prove the power supply is not the problem, there's a way to "jump start" it similar to what you can do on modern ATX power supplies. It won't work all the way because it needs a load attached to work correctly, but it should at least confirm that the power supply works. You can do it by shorting the /PFW and the +5V trickle pins together with a paperclip or something. Pins 9 and 10 on the power supply. When I do this on my working IIci power supplies, I hear a relay click (or something) and the fan starts spinning slowly and silently. The power supply won't start up all the way and the output voltages won't be correct (due to no load being attached, I believe) but the spinning fan should at least confirm that the power supply's startup circuit works...here's a diagram I threw together. I *think* it's right according to pinouts I found online and my continuity tester, but I definitely tested shorting pin 9 and 10 as indicated on the picture.



If that works, then I would almost certainly say it's something on the logic board...also, I can't speak for the IIcx, but the IIci doesn't need a working PRAM battery to boot.

 

[volvo242gt]

Yep. It'll just sometimes take a little work to get going - the replacement IIci board that's in my main machine did take a few tries to get going with the dead PRAM battery installed. Strangely enough, that dead PRAM battery had enough juice to keep the original manufacture date intact. TechTool reports 4/22/90 as the manufacture date on my ci.

-J

 

[James1095]

I doubt the power switch is at fault, but if you suspect it, measure it with an ohm meter. It's a double pole switch, both sets of contacts should have continuity when the button is pressed and open circuit when released.

 

[olePigeon]

You could always upgrade the Power Supply to an ATX. It's really straight forward (as in, just match the colors of the wires). I couldn't get the soft-power modification to work, but that's OK. My IIci now boots like an LC.

 

[mcdermd]

After uniserver told me to go back and recheck all the traces in the soft power circuit one more tim, I saw it - a broken trace. I tested it with the meter and sure enough, it was bad. After a quick repair between vias (and putting caps C15 and C16 back on), it is working perfectly:



http://i46.tinypic.com/35mif7m.jpg

Time to seal it with nail polish and button it back up now.

 

[uniserver]

I am working on this IIci, I got it for free but the catch was, he had previously tried to recap it, it was bad, lifted pads, burned spots on the pcb, etc, I finally got it working. Traced the traces lol. sometimes you just gotta be patient.

I was having soft power issues my self with it, i ended up replacing the big round 470uf 16v caps and

all started working fine. Those caps looked just fine too.

Also i had a LC-II recapped, and after it didn't boot or anything…

i got frustrated… took a break came back… did some close inspection,

saw a tiny solder speck bridging 2 pins on the VLSI chip… picked it out with my dental pick.

and boom it booted and works fine. Its the little things that can get ya.

Frustration can get the best of you. and having the right tools for the job just stacks the cards for success in your favor.

even a experienced cap-tech can hit a wall, sometimes.

Heck, Sometimes a doctor needs a doctor

 

[Juror22]

This has been an incredibly helpful thread. I have been working through my own IIcx power issues, after I bought one on eBay a while back for the nubus cards inside and I thought it would be nice to get running. So far it looks like the power supply is good, I recapped it, replaced the PRAM battery, but it is still totally silent.

I'm still looking for that corroded or shorted something - just wanted to thank everyone for all the great ideas and info.

 

[uniserver]

look for eaten up traces, also try to unplug the psu, then turn the power switch so it sticks in and stays fully engaged, then plug it in and wait, maybe after 30 seconds it will just come on .

worst case scenario you can short one of the pins on the power connector that will make it go on, per dougg3's graphic.

 

[Bunsen]

Hi folks, just a quick reminder - whenever possible, it would be great if you could upload images to these threads as local files. Don't worry about space, we have plenty. This helps us not to lose relevant images in old threads.

I've localized a couple of images above, as noted in the edit comments.

Cheers.

 

[Trash80toHP_Mini]

Time to seal it with nail polish and button it back up now.

Where'd you get that trick? The patch wires I've seen appear to have been tacked at the corners where the follow the paths of the subsurface traces.

 

[Juror22]

I still haven't found any bad traces, there are some mildly (surface) corroded pins on the chips (see pic, sorry about the flash,this was the best one - circled red ones are bad, green one is good) is there any way to get rid of the corrosion, do I need to re-solder these? I did clean the board when recapping, so there is no residue.

The power switch does not stay in without mechanically holding it in and does not power on the computer, even when left on for a good while. (I don't remember if that is normal behavior or not, was this switch supposed to actually 'catch' when pushed in and release when pushed again, or was the only way to keep it pushed in, to align the button so that it was in the 'latched' (vertical) position?

Shorting PSU pins 9/10 with the PSU plugged in and the board supported does work to power it on, and it appeared that the floppy drive was reading, but it did not chime, when I tried this. The power switch would not shut it off either (the only way was to unplug it).