68kMLA Classic Interface

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Mac IIci broken pins on the CPU. What to do?
Posted by: geokov on 2024-01-12 20:53:58 I just finished removing all the old caps from my IIci and cleaned the board. I was happy that after the cleaning all the chips on the board looked good, even the ones in the areas with the caps that tend to leak and damage them. But then I noticed the CPU chip. Darn it, one broken pin and two hanging on by a thread. Does anyone have experience with this? Would it be repairable or is a new CPU chip needed? Sad because the pads and traces around it seem to be in pretty good shape.
Posted by: ymk on 2024-01-12 21:38:40 Looks like you lost the /AS pin. I think you're looking at a new CPU. The good news is they're not expensive.
Posted by: geokov on 2024-01-22 13:02:29 Looks like you lost the /AS pin. I think you're looking at a new CPU. The good news is they're not expensive. Thanks for the reply, I think you're right that I'll need a new one. I'm going to try to repair it first just for fun but I doubt it will work.
Posted by: Phipli on 2024-01-22 13:11:00 Thanks for the reply, I think you're right that I'll need a new one. I'm going to try to repair it first just for fun but I doubt it will work. Truth be told it looks possibly repairable. That worst pin, use a needle to bend it back straight. Start from the end of the row under the other pins to lift it up, then use the point from above to line it up with the stub on the package. Scratch the pin gently to get a bit of fresh metal. Put a little flux on it and the stub. Cut a short bit of solder and leave it sat waiting on a heat mat. Use a scalpel blade to gently hold the soldered foot of the pin. Do not move, do not slip, do not wobble. While holding the foot with the scalpel, clean your iron, the. Touch the tip to the cut piece of solder so there is a small amount on the tip, wipe it onto the broken pin and lift the iron away in one movement. Assess. Did you join the break? Did you bridge to other pins? If it isn't perfect, hold the foot with the knife again, put a tiny bit more flux on the location and touch the iron to it briefly. The really important thing is don't let the pin move too far. You need to keep it still with the knife. Best I'd the foot end doesn't get hot enough to melt, so speed and not too higher iron temp is ideal... Or find a new chip and solder it in. Make sure you get a new chip with straight pins. It's a pain if they've been bent. No harm in trying to fix this one first though 🙂
Posted by: geokov on 2024-01-22 13:17:51 Truth be told it looks possibly repairable. That worst pin, use a needle to bend it back straight. Start from the end of the row under the other pins to lift it up, then use the point from above to line it up with the stub on the package. Scratch the pin gently to get a bit of fresh metal. Put a little flux on it and the stub. Cut a short bit of solder and leave it sat waiting on a heat mat. Use a scalpel blade to gently hold the soldered foot of the pin. Do not move, do not slip, do not wobble. While holding the foot with the scalpel, clean your iron, the. Touch the tip to the cut piece of solder so there is a small amount on the tip, wipe it onto the broken pin and lift the iron away in one movement. Assess. Did you join the break? Did you bridge to other pins? If it isn't perfect, hold the foot with the knife again, put a tiny bit more flux on the location and touch the iron to it briefly. The really important thing is don't let the pin move too far. You need to keep it still with the knife. Best I'd the foot end doesn't get hot enough to melt, so speed and not too higher iron temp is ideal... Or find a new chip and solder it in. Make sure you get a new chip with straight pins. It's a pain if they've been bent. No harm in trying to fix this one first though 🙂 Hi, Phipli, thank you for your very helpful answer, I figure I have nothing to lose with trying to fix it, I do like a challenge. 🙂
Posted by: Phipli on 2024-01-22 13:19:38 Hi, Phipli, thank you for your very helpful answer, I figure I have nothing to lose with trying to fix it, I do like a challenge. 🙂 You only want a very small amount of solder. Just enough to make the bridge, so aim for like, a 1mm cube of solder to put on the iron. Good luck!
Posted by: geokov on 2024-01-22 13:25:07 You only want a very small amount of solder. Just enough to make the bridge, so aim for like, a 1mm cube of solder to put on the iron. Good luck! Thanks for the tip, I'm going to try it.
Posted by: joshc on 2024-01-22 19:30:36 The plastic cap of the chip can be scraped back to reveal more of the pin - it’s not easy but if done right it would give you more area to bridge to. But try what Phipli said first, you might be able to work with what’s there. I’ve managed a small bodge on 68030 pins on a damaged Classic II board before. Good luck.
Posted by: GRudolf94 on 2024-01-23 05:34:55 68030s are C(eramic)QFP - grinding into that alumina isn't really viable.
Posted by: joshc on 2024-01-23 05:55:30 Ah my mistake, I thought they were plastic. I managed to do it with a Classic II but not sure if those are different.
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