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Author Topic: Does anyone have a spare Lisa motherboard?  (Read 3347 times)

AlexTheCat123

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Does anyone have a spare Lisa motherboard?
« on: November 02, 2019, 06:17:35 pm »

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
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rayarachelian

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Re: Does anyone have a spare Lisa motherboard?
« Reply #1 on: November 03, 2019, 08:27:06 am »

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.)
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #2 on: November 03, 2019, 09:02:53 am »

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?
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rayarachelian

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Re: Does anyone have a spare Lisa motherboard?
« Reply #3 on: November 03, 2019, 11:43:09 am »

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.
« Last Edit: November 03, 2019, 11:54:00 am by rayarachelian »
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #4 on: November 04, 2019, 06:22:28 pm »

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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rayarachelian

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Re: Does anyone have a spare Lisa motherboard?
« Reply #5 on: November 05, 2019, 10:14:28 am »

Take a look here: http://bitsavers.org/pdf/apple/lisa/hardware/lisa-motherboard-enhanced.pdf
It's a bit difficult to read since it's grayscale and hasn't been cleaned up, but zoom in and it is legible.
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #6 on: November 05, 2019, 07:16:40 pm »

I just desoldered the connector for the I/O board and I found that some of the pads underneath the connector have been corroded away. I also lifted a few pads on the bottom of the board when I was desoldering it. How should I go about repairing this damage or is the board just toast?
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rayarachelian

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Re: Does anyone have a spare Lisa motherboard?
« Reply #7 on: November 05, 2019, 08:42:12 pm »

I just desoldered the connector for the I/O board and I found that some of the pads underneath the connector have been corroded away. I also lifted a few pads on the bottom of the board when I was desoldering it. How should I go about repairing this damage or is the board just toast?

So at this point I'd say, take a deep breath and say "It's a good day to die" like a Klingon, and then accept that this board is dead.
Now that doesn't mean you throw it out, it means you're free to do whatever you need to do to get it working again and, if you can't, you don't worry about being disappointed. However, whether you do get it to work or not, you'll have learned some really neat skills.

It's probably toast for the fully corroded pads as the corrosion will travel through the trace over time. The lifted pads might go back on if you go very gently, and they can be repaired.

You can try reflowing the solder on the corroded pads if enough material is left, then measure connectivity to the other end. If you get near zero ohms, you're fine.  This is a long shot, but a conductive metal paint pen might help, likely it won't.  like this: https://www.amazon.com/Bare-Conductive-Electric-Paint-10ml/dp/B00KBXT6JW/  More likely, if you can follow the trace to the other end, solder a copper wire to it and route it back to the lifted pad then solder the other end of the wire directly to the connector's pin or whatever attaches to the pad you should be good. Be sure to glue that wire down to the board so it won't move.

There are techniques for repairing lifted pads which might help: https://www.instructables.com/id/Repairing-a-Damaged-Pad-on-a-PCB/ - this following video is for SMD so it's going to be a lot easier on the Lisa.  https://www.youtube.com/watch?v=YQdqX0DxBXM - google around some more, you might find better stuff than this.

Assuming you don't give up and make it to the end, once you're done and it works again, you should seal the board with some laquer - possibly krylon spray could work, or nail polish, not sure if you can get proper conformal varnish like this: https://www.amazon.com/MG-Chemicals-422B-340G-Silicone-Conformal/dp/B008O9YGQI/

I do have a similar lisa to fix, like yours, but instead, only on both a CPU and an I/O board: https://lisalist2.com/index.php/topic,18.0.html so yeah I feel your pain.
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #8 on: November 06, 2019, 01:27:56 pm »

I just looked more closely at the motherboard schematic and it looks like most of the pads that are corroded away connect to the serial ports and the few that do not should be easily repairable. Would it damage anything if I fixed everything but the serial ports and just used the Lisa without them?
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rayarachelian

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Re: Does anyone have a spare Lisa motherboard?
« Reply #9 on: November 07, 2019, 06:19:17 am »

I just looked more closely at the motherboard schematic and it looks like most of the pads that are corroded away connect to the serial ports and the few that do not should be easily repairable. Would it damage anything if I fixed everything but the serial ports and just used the Lisa without them?

Unless you want to use LisaTerm or BLU or Zterm, you should be fine without the serial ports.
That said, BLU is a really useful tool, off the top of my head, I think BLU wants serial port B with hardware handshaking, so if you can fix port B, you'll be in good shape.

You'll want to at least fix the signal ground, RX, and TX lines, though you'll likely need the handshaking lines too.

see: https://www.lammertbies.nl/comm/cable/RS-232.html especially the section that shows a table labeled "DB9 - DB25 conversion" cable with hardware handshaking. The pins on the DB25 side are the ones you care about on port B.

Now, if you have a classic 68k Mac that has a GCR capable floppy drive, even if it's a super drive, you should be able to make Lisa floppies, though one with an 800k floppy drive is preferred due to the head width. And in that case you might not need to use BLU. (Don't bother with USB floppy drives, they're just MFM PC drives only - I think there might have been one that supports GCR, but they're as probably as rare as Lisa 1s.)

You'd transfer disk images to that Mac, and then make the disks on that Mac and insert them into the Lisa.
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #10 on: November 07, 2019, 08:28:04 am »

I have some old Macs with 800K drives, so making floppies should not be a problem. I will try to get the Lisa working first and then I might try to fix the serial ports if I can get it powering on.
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Lisa2

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Re: Does anyone have a spare Lisa motherboard?
« Reply #11 on: November 07, 2019, 12:14:33 pm »

Now, if you have a classic 68k Mac that has a GCR capable floppy drive, even if it's a super drive, you should be able to make Lisa floppies, though one with an 800k floppy drive is preferred due to the head width.

Ray, I think you are remembering an issue with PC 5.25" HD drives writing DD formats.

To clarify (not to hijack this thread), the number of tracks (and head width) is the same for the Macintosh DD (800K) and HD (Super) Drives.   Some later mac FDCs had issues writing Lisa disk images in a way that the Lisa's FDC prefered, but the drive itself was never the issue.

Rick
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #12 on: November 09, 2019, 04:28:24 pm »

I have cleaned up the corrosion, replaced several corroded parts on the motherboard, and have tested every single connection on the board (which took a very long time) and there is an improvement! The light on the power switch illuminates when I press it and will stay on for a short period of time (maybe about one second), but then turns off again. Is this a common problem and does it narrow down any potential faults with the computer?
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rayarachelian

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Re: Does anyone have a spare Lisa motherboard?
« Reply #13 on: November 09, 2019, 05:10:07 pm »

Quote
I have cleaned up the corrosion, replaced several corroded parts on the motherboard, and have tested every single connection on the board (which took a very long time) and there is an improvement! The light on the power switch illuminates when I press it and will stay on for a short period of time (maybe about one second), but then turns off again. Is this a common problem and does it narrow down any potential faults with the computer?
Yes! That's a great sign!
Most likely your next issue is either 1. the I/O board traces around the COP421, or 2. the power supply is weak and needs new capacitors. 2 (power supply capacitors) is even more strongly indicated if you hear some ticking, though the light on the switch would only stay on while the button is pushed, if it stays on after you let go of this switch, it might not be this, but I'd check the large capacitors in the power supply either way, if you see cracks in the large rectangular yellow ones (if they're yellow and somewhat transparent, they're the original ones, and are likely long dead), and the large cylindrical electrolytics.

I've also seen this caused by the floppy cable inserted backwards in the LisaLite card.
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AlexTheCat123

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Re: Does anyone have a spare Lisa motherboard?
« Reply #14 on: November 12, 2019, 07:53:33 pm »

I think I'm making progress! I have patched every bad trace that I can find on the I/O board and now the power light will turn on and stay on when I hit the switch. A transistor (Q3 or Q4 I think) let out some magic smoke when I turned it on for the first time, but it seems to be part of the audio amplifier, so I don't think it is necessary, at least for now. If I press the power switch again after turning the computer on, it will turn back off, but only if I let it run for about 20 seconds before trying to power off. There is still nothing on the display, though. I don't even hear the high-pitched whine that CRTs make when they are on, so I suspect that there is something wrong with the circuitry that drives it. Does the CRT turn on when you press the power switch or does it require a signal from a board in the card cage before it energizes? If it requires some sort of signal before it turns on, then I probably have a problem with the CPU or I/O board, but if it turns on with the rest of the computer, then I may have to mess with the video board to make it functional.
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