I couldn't resist snatching up a non-booting 660av on eBay for $25. The battery hadn't leaked, so I figured it probably just needed a recapping. It was sold as non-booting, but the seller could hear the hard drive spin up.
When it arrived I powered it on. I actually got video output, but it was garbled and the hard drive had trouble spinning up and booting. I don't care about the hard drive since I can replace it with a SCSI2SD. The video output had me a little concerned though. I started looking around on the board.
I didn't pay close enough attention to the picture in the auction. It looks like it's been exposed to moisture of some kind. There was rust on the CD drive. The worst part was the legs of the CIVIC (Cyclone Integrated Video Interfaces Controller). This is an Apple ASIC that appears to act as the intermediary between the VRAM and everything else from what I can tell in the 660av/840av devnote. You can see the green on the legs in the picture below (the wetness on the bottom of the chip is some flux I put on to try to reflow the solder):
I guess it was partly good news and partly bad news. The good news was that the video was screwed up and I had a pretty good guess for what was causing it. The bad news was that it was corrosion.
I used hot air to remove the chip. First I covered the surrounding part of the PCB with Kapton tape and then covered that tape with aluminum foil tape. The whole idea was to protect the surrounding components. I've been told that putting Kapton tape down first makes it easier to remove the aluminum tape. After trying it, I would definitely have to agree with that. Then I used a thermocouple to measure the temperature and went around and around and around the chip with the hot air nozzle. When it got hot enough I was able to lift the chip off, and here's what the pads looked like:
This was good news; none of the pads were gone. A lot of these pads really did not want to take any solder, so I had to do some cleaning. I used a pencil eraser which worked pretty well. After the eraser and solder wick, it looked more like this. Still not perfect, but much better (some of the weird bits you see in the middle are pieces of pencil eraser I cleaned off later):
As you can see, some of the vias still have some damage and the corrosion has probably already gone into them. There's not much I can do about it. For $25 I won't be too upset if it eventually fails.
That completed the pads, but the chip was pretty bad too. I tried lots of things on the chip legs. I did the pencil eraser as best as I could, I tried red DeoxIT, and I tried scraping corrosion off with an X-Acto knife. I thought I had the bottoms of the legs looking pretty good so I put some solder paste onto the board and put the chip back on. Unfortunately something still wasn't right and I could only make it work if I pressed down on the chip. The display also had vertical stripes if I went into thousands of colors mode.
Finally, I got some fine-grit sandpaper (400, 600, 1000) based on advice from balrog. It's pretty tough to use sandpaper on small IC legs, but I think it may have helped clean some of the corrosion off. I did a little bit of sanding with the chip soldered down because it felt less risky that way. I removed the chip with hot air again and did some more careful sanding on the legs. I finally began flooding the legs with flux and solder until I felt like the legs looked clean and were taking solder well. I ended up cleaning off a lot of gunk, although I think a lot of it was just flux residue.
With cleaner-looking legs I felt more comfortable doing drag soldering. I did have a few hiccups where a few of the legs didn't solder down at first and I ended up with chimes of death, but I was able to find and fix them. I also lifted a pad while trying to separate two legs that I accidentally soldered together (oops!), but the pad is still attached to its trace and it's a nice thick power trace. I'm not too worried.
It looks a lot better now. Not perfect, but way, way better:
Last night it wasn't booting at all, which I'm almost thinking I should blame on the capacitors because the startup chime was all garbled (when it even played). This morning I did some cleaning with isopropyl alcohol around the CIVIC and the caps, and now everything is working great. I will definitely replace the caps, stick a SCSI2SD in there, and call it good.
Here is a "selfie" that the 660av took of itself through a camcorder hooked up to its composite input jack.
I burned myself with hot solder wick twice last night and then cut my hand on the case. I was almost about to go "Office Space" on this computer, but I'm glad it finally seems to be happy now.
Haha, that selfie is legit! Great work and tips on removing the chip. Kapton tape is a great idea along with the aluminum tape.
So it looks like if there is enough corrosion, the solder joints become brittle or loose and the IC legs start to delaminate from the pads and lose conductivity. What kind of hot air rework station are you using? I am thinking of getting one.
I have removed large ICs like this before, Not fun I assure you, but I have.
I am actually watching a 200Mhz PPC603ev on ebay to see if I can get it cheap enough. Want to do a swap on my spare Duo 2300 motherboard to bump it to 200Mhz. Only issue is, I dont know if the multiplier will let me get that high due to the paltry 33Mhz bus speed. the chip can do 4X, but I may need to overclock the bus a bit.
Thanks tt! I got the Kapton tape and aluminum tape combination idea from videos by RetroGameModz on YouTube. He repairs old Amigas. In particular, this video where he replaces a chip on a plasma TV was interesting:
What you said about the corrosion absolutely seems to be the case; you can lose connectivity from the pads. It was mostly working, so I think maybe only a pin or two was actually having connection problems, but it was beyond the point of being fixable without yanking the whole chip out and cleaning everything.
In particular I think this machine has been exposed to moisture. There's also some white stuff that doesn't want to come off the bottom of the board.
The hot air station I got is the X-Tronic 5040-XTS. It works pretty well. I haven't tested the soldering iron part of it, and the 660av's board was way too big to use with the preheater. I just used one of the included nozzles. I know they make nozzles that are meant for directly removing QFP chips but just going around and around with a regular nozzle worked. It honestly wasn't too annoying to remove. It probably would be a little more scary if I had something to lose
I've been kind of freaking out after the repair because I've been getting a black screen when I turn it on, especially the first time after plugging it in. That's scary especially after resoldering the framebuffer IC. I did some more research, and I'm pretty sure everything's fine. What I'm seeing is the issue that the 660av is one of the Macs that sometimes boots with a black screen if the PRAM battery is dead. Every time I see the problem it's when there's no PRAM battery installed. Whenever I put a good PRAM battery in, everything works perfectly, so I'm 99.9% sure that's the issue.
The sound output is also terrible sometimes. It cuts in and out. I'm hoping that's just due to bad caps.
I replaced all of the SMT aluminum electrolytics with tantalums and now everything works great, no sound problems at all and it boots fine with a PRAM battery installed. The interesting thing is that the board already had some tantalums, but all of the tantalums use a different silkscreen marking that doesn't seem to indicate polarity. Maybe the polarity marking is underneath. So it seems that they explicitly chose to use tantalums for those caps versus aluminum electrolytics on the others. Whatever the case, tantalums seem to work fine.
The other interesting thing was that the capacitors were glued down with two drops of some dark brown glue or epoxy or something. This is the first Mac I've ever run into that had caps glued down. I wasn't sure exactly how to remove the glue, so I left it there. Doesn't seem to hurt anything. I probably would have had trouble with the glue if I had been using my iron, so I'm glad I used hot air this time.
Now that I've removed the caps using hot air on multiple logic boards with no trouble at all, I can definitely say it's my preferred method of cap removal. I think it's too easy to accidentally lift a pad if you just use a single iron. Dual irons probably work fine too, but the advantage of hot air is you can work in tighter spaces. I just go over the leads of the capacitor I want to remove back and forth with the rework wand. My other hand holds tweezers which I use to try to move the capacitor every so often. As soon as the capacitor starts allowing me to move it, I can easily lift it off with no damage to the pads at all. Then I usually put more solder onto the pads to freshen them, and finally remove it all with wick, leaving nice shiny pads behind.
This time I actually put the replacement tantalums in with solder paste and hot air. I just wasn't in the mood to fit the iron tip into tight spaces. The paste worked fine, although you want to make sure you heat everything long enough so you don't end up with any leftover liquid paste. I'd probably prefer just using an iron and a spool of solder to put the new ones in, but the tight spaces were the dealbreaker.
Anyway, it feels good to have brought this sweet machine back to 100% good health again. I guess I need to test the caddy-loading CD drive to make sure it still works, but that can wait.