restoring a battery-bombed IIcx

[Phipli]

A little update: still waiting for caps, but I removed all the old caps without any trouble - my first time doing this. The battery holder was a royal pain, though. I spent an absurd amount of time trying to get the remnants of the old battery holder's negative lead out of the PCB, using the iron, a second iron with a spring-loaded suction, and pliers. I tried every which way pushing, pulling, and heating, but I couldn't dislodge the 2mm piece of the old battery lead that's stuck in the through hole. I had to admit defeat and give up, so attaching the new battery holder is going to require some creativity.

Yup. Cursed ground plain.

You want to try removing the axial caps on the power plains on a Mac II/IIx.

Hakko solder removal gun has the grunt to remove the solder.

Otherwise, use low temperature solder and mix it with the existing solder. The type of stuff that you get as solder paste with something like 150°C melting point.

Or chipquick if you've got some.

 

[bigmessowires]

I actually have some 10-year-old ChipQuik here that I never found a use for. But there's nothing left sticking out of the board that I can grab on to and pull. Maybe ChipQuick would give me enough time to heat both sides, set down the iron, and push something into the through hole to dislodge the remnant of the old battery lead.

 

[Phipli]

I actually have some 10-year-old ChipQuik here that I never found a use for. But there's nothing left sticking out of the board that I can grab on to and pull. Maybe ChipQuick would give me enough time to heat both sides, set down the iron, and push something into the through hole to dislodge the remnant of the old battery lead.

Yup, that would work. You need to get it to mix though. Fill the hole from both sides and try to get the original solder melted. You might need to turn your iron up. Things like this I have to turn my underpowered iron up to 380 or even 400°C. Add flux. Flux is your friend (but not your lungs friend).

Use something smooth and stainless steel to push it out. Solder sticks to it less well and it probably won't get stuck itself.

 

[bigmessowires]

I'm still waiting on replacement axial electrolytics for the three biggest caps, but recapping of all the SMD capacitors is done:



And there's some improvement. Now the IIcx turns on and off normally with the power switch, and also turns on normally from the keyboard power button. But that's all. There's no chime, and no video. Rats.

I'm thinking I should probably beep out the RAM and ROM pathways next? Or maybe start by closely inspecting all the traces near the capacitors? Are there any obvious signals I could examine with the scope that might hint what is and isn't working?

 

[Phipli]

I'm thinking I should probably beep out the RAM and ROM pathways next? Or maybe start by closely inspecting all the traces near the capacitors? Are there any obvious signals I could examine with the scope that might hint what is and isn't working?

Start by visually inspecting the sound chips area. One of them controls reset. They're also surrounded by capacitors that often damage traces.

When looking for a chime, it is better to use an external speaker from the 3.5mm jack, rather than the built in speaker.

While powered on does the CPU get warm?

Check that the clocks are working...

Then check the ROM area. The computer would usually death chime if RAM was an issue.

 

[bigmessowires]

Thanks for sticking with me on this. I haven't checked 100 percent of the sound chips, but they look OK visually and all the top-side traces checked OK.

Something very interesting just happened: I turned on the computer and left it running while I went to look for my multimeter. After what seemed like about 30-60 seconds, I heard the chime of death! Exciting.

I didn't have a video card installed at the time, so I powered off, installed my oldest Toby card (tested and working in my IIci), and powered on again. This time I got the chime of death immediately, but no video.

Powered off, waited a minute, and powered on again: got the chime of death immediately, but still no video.

I thought maybe the presence of the Toby card was helping somehow. So I powered off once more, removed the video card, and powered on again: still got the chime of death immediately.

This is good progress, though I can't explain why it went from a very delayed chime of death to an immediate chime of death. Maybe residual voltage left on some capacitors while turned off is affecting the behavior on the next power-up. Too bad I don't have any video working - the sad mac code might tell me something useful. I think RAM is the next thing to check. I can try swapping the RAM from my IIci, but I don't want to mess with the RAM too much since the SIMM sockets are brittle plastic and one is already broken. Bad RAM also wouldn't explain why there's no video, but there could certainly be more than one problem.

 

[bigmessowires]

I tried booting with a ROM-inator and jumper W1 removed, but I either get a buzzing sound or silence. I think it's OK to leave RAM bank B empty on the IIcx, right? That might help narrow down the possibilities. RAM bank A did have battery sludge in it (see the photo in my first post), although it seemed to clean up surprisingly well and I didn't notice any visibly damaged traces. I found another old thread about a IIcx with similar problems, and fixing the RAM issue on that one also caused the video to start working. So maybe it all comes down to RAM.

 

[bigmessowires]

Oh, I just noticed that the six 74F258 chips next to the power circuit are RAM muxes. A few of those chips look pretty terrible on this motherboard, so that could definitely be causing a RAM problem.

 

[joshc]

I see quite a few damaged traces around there too, checked those yet?

 

[bigmessowires]

Many of the traces in that area look bad, and especially many of the vias look absolutely terrible. But except for three that I repaired, so far they've mostly tested OK. For those particular traces in the photo, I'm not sure which chips they're connected to since they're just isolated traces running between two vias. I could try testing for continuity between the vias, or try to visually trace the connection on the bottom side and see where it goes.

My bet is on those 74F258 RAM mux chips. A couple of them look pretty bad. You can see them in the photo from my first post here: https://68kmla.org/bb/index.php?threads/restoring-a-battery-bombed-iicx.45678/#post-506095

 

[Phipli]

or try to visually trace the connection on the bottom side and see where it goes.

That's what I usually do. You'll lose your place, so take a photo, and draw the route over it. Saves having to start again, and you have it for future reference.

 

[bigmessowires]

It chimes! There's video. IT BOOOOOOTS!!!





Oh, happy day! Another IIcx saved from the scrap heap. The only thing I changed was the RAM, removing the existing RAM and substituting some RAM from my SE/30. I think I can see exactly which RAM SIMM is bad, it's the one that was sitting in a puddle of battery goo and is visibly corroded. Maybe I can clean up those pads enough to get this SIMM working again.



In total, the only fixes I made to this battery-bombed IIcx were:

• clean it with 99% alcohol
• repair three broken traces in the start-up circuit
• recap the SMD capacitors with tantalums
• replace the RAM in bank A

I think the -5V supply is broken, so I still need to fix that, though I'm not sure which computer functions need -5V. I'll spend some time testing the other functions like SCSI, serial ports, all the NuBus slots, etc. Then I still need to replace the battery holder and the big axial caps. Finally, I plan to give everything a nice wash with hot water and soap, then flood it with isopropyl, so that any remaining corrosive junk will hopefully be washed away.

Woohoo! Celebration time! It's time for a little Macintosh IIcx party.

 

[jmacz]

Congrats!

That feeling when you fix a dead Macintosh and it chimes, boots, and gets to the Finder... so addicting. And so damaging for your wallet because you end up picking up more 'dead' machines just to relive it.

 

[Phipli]

It chimes! There's video. IT BOOOOOOTS!!!

Congratulations

though I'm not sure which computer functions need -5V

Sound and Serial.

 

[bigmessowires]

Congratulations

Thanks! This is the first damaged Mac that I've managed to fix. The case is in pretty nice condition, so it'll make a good showpiece when finished.

I wasn't able to salvage that corroded RAM SIMM, so I only have 5 MB RAM scrounged from other computers. Test results so far look pretty good:

• Both ADB ports work
• All NuBus slots work
• internal and external floppy work
• reset switch ok
• power switch works
• ADB power button works
• soft power-off works
• SCSI external and internal works
• original PSU works (will recap it anyway), fan is loud
• front speaker works
• stereo sound works (tested with headphones)

Still to do:

• Fix -5V and test the serial ports
• Fix the battery holder negative terminal footprint and install a new battery holder
• Install a fancy blue power LED
• Two different ROM-inators didn't work (tested working in an SE/30), but an original SE/30 ROM SIMM works. All tested with jumper W1 removed. Hmm...
• IIcx sometimes turns on immediately when plugged in, with the original PSU or with an ATX PSU. But after that it turns off normally and stays off as expected. I think it's the job of C9 and R30 to prevent this, so I'll double-check those.

 

[Phipli]

Install a fancy blue power LED

Blue? I'm more childish than that.

I also put one in my dad's IIci without telling him when I recapped and repaired it, then hoped he wouldn't mind. Thankfully he thought it was funny and didn't take me up in the offer to put it back.

There is a current limiting resistor next to the LED that you can replace to adjust the brightness btw.

To help check the machine over you could run MacTest Pro, the apple hardware test suite. Second download here :

MacTest Pro - Macintosh Garden

MacTest Pro is repair-oriented diagnostic software that can test logic boards, video cards, monitors, floppy drives, hard drives, and CD ROM drives. It can also detect software corruption problems, and the existence of multiple System Folders on a volume. MacTest Pro is intended for use by Apple...

macintoshgarden.org

 

[joshc]

Lovely.

"Well...we have lift off...I think"

 

[Phipli]

Lovely.

"Well...we have lift off...I think"

I feel like they want me to buy MatLab... That or MathCAD.

 

[bigmessowires]

An RGB color changing LED... nice! I fixed -5V and both serial ports tested OK (thank you, Imagewriter II). But I wasn't able to cure the instant-on when the computer is first plugged in. The rest of the power-on and power-off behavior is normal, so it's a minor annoyance but I'd like to fix it.

As for the RAM, now I'm less sure whether the problem was the RAM itself, or the high-order address lines in the RAM SIMM socket.

• Original RAM with the battery damage was 4x4MB SIMMs, and caused chimes of death at startup.
• Swapping in 4x1MB SIMMs from a working SE/30 got the IIcx to boot.
• Swapping the damaged 4x4MB SIMMs into the SE/30 also causes chimes of death.
• But installing another set of known-working 4x4MB SIMMs in the IIcx still results in chimes of death?!

 

[Phipli]

But I wasn't able to cure the instant-on when the computer is first plugged in.

The power button is a latching design. Try rotating it.

Although... Hum. You say it behaves after that? I'd expect it to repower up anytime you shut down if that was the issue. Weird.

Perhaps an issue in the soft power circuit then.