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Does anyone have a spare Lisa motherboard?

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AlexTheCat123:
Hello! I just got my first Lisa in the mail (a Lisa 2/5) and it has the usual battery corrosion problem that plaques so many of these machines. I am now trying to clean up the corrosion and I think that I will be able to repair all of the boards except for the motherboard, which is probably beyond repair. Does anyone have a spare motherboard that I can purchase to get my Lisa working?

Thanks!
Alex

rayarachelian:
How bad is your current board? What's damaged on it?

There is one on ebay that's listed for parts, but it looks like the CPU and I/O board connectors are messed up. If your connectors and parts are good, you could try that one.  The two memory edge connectors are identical to each, and the CPU and I/O board connectors are also identical to each other (just offset horizontally). So you may be able to use an I/O edge connector for a CPU board connector in another board and vice versa.

The ZIF connectors on the expansion slots are the hardest things to find replacements for, so be careful to save those.

You could also buy a new one from here: http://vintagemicros.com/catalog/brand-apple-lisa-motherboard-lisa-lisa-p-299.html but this looks like a bare board without connectors, chips, or other parts,, so as long as you've got the time to move all the components over, you should be fine.

If by some chance you run across a 2/10 motherboard, you could use the parts from it, but don't use the actual board in a 2/5 as you'll lose the parallel connector (unless you rewrite the chassis with a 2/10 set of data and power cables.)

AlexTheCat123:
Unfortunately, the connectors for the CPU and I/O boards are damaged, so the board off of eBay will not work. Luckily, the ZIF connectors are fine. All of the ports on the back of the board are rusted as well. I could probably find replacements for these parts, but I do not have the necessary desoldering equipment to get the old ones out of the board. There are just so many pins to desolder and I would probably end up damaging the board with excessive heat. I am tempted to just fire it up in its current condition (after I clean off the corrosion) and see what happens, but I am sort of nervous about doing this. Do you think that this is a good idea or am I likely to further damage it?

rayarachelian:
If you give it a good cleaning, and then reflow the solder on the corroded connections with lots of flux before you turn it on, it might be good enough.
Be sure to blow out any cruft from under the chips that are soldered on as well. Heating up corroded pins on chips and reflowing the solder will help too.

If you're creative and handy you might be able to fix the clips on those broken CPU and I/O board connectors on that board. You'd need to figure out what shape they are by extracting one of the old ones, and cutting a new one, then carefully inserting the new one in. Just be careful to not allow it to get loose and short out a pin next to it.


If the corrosion made it all the way inside the traces inside the board, you'd have to to use a VOM set to continuity testing and beep out the connections, should a connection not work, you'd have to add a jumper wire and glue it to the board. But then, over time, it'll just keep eating traces and it will fail again.

You wouldn't need super specialized equipment to desolder, just a desoldering sucker with a soldering iron. There are cheap ones that have both the pump and a soldering iron together like this for under $10: https://www.amazon.com/Velleman-VTDESOL3U-Vacuum-Desoldering-Heater/dp/B00B88FRME/
You'd still be doing it single pin at a time. The only danger is from overheating a pin and lifting a pad, or damaging the pin on the connector, if you're not careful enough.

Give it a shot, if it's already dead, you don't have much to lose.

John used to have the fully populated motherboards over at Vintage Micros, maybe reach out to him and see if he has any left if you don't have the time to invest and just want it to work.

Edit: When my MBP17" died with a GPU failure, I bought one of these for ~$40: https://www.amazon.com/Kohree-Rework-Station-Solder-Digital/dp/B00JVM3WBC/ - it's basically a hot air gun whose temperature you can precisely control. You could use this along with a lot of liquid flux to either reflow solder on the back of the board, or even to help desolder the board. Be careful with it to avoid melting the board or components. I'd look up the temperature of leaded solder, such as is used in the Lisa first and set it to that.

In my case I used this to reflow the GPU in my old 17" macbook pro as I said, so if you've got some old Macs that might have that same issue, it might be worth investing in. Would work on other things where the BGA connectors can fail, like Sony Playstations. I've used this thing 3x already, so it more than paid for itself by getting another 2 years out of an otherwise dead machine.

I'd be careful to not overheat the solder joints if you're just reflowing them with this thing, otherwise, they'd melt and fall through the other side. So you'd want a quick pass once or twice, just enough to make the solder go liquid but not more than that.

I'd practice on some old electronics junk first like old PC boards or radios or whatever that are broken and you don't care about.

AlexTheCat123:
I have decided to give it a shot, but I may need some help with the component values on the motherboard. A few of the parts are so corroded that I can't read them at all. Can someone tell me the part numbers of Q1, Q2, C12, and the resistor packs that connect to the ports on the back? I ordered some desoldering wick and I will try removing a few of the damaged parts over the next few days.

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