LisaList2

Advanced search  

News:

2019.06.07 fixed NChat for the "Curve" theme, will eventually move it to its own page and add it to the default theme as well. Other plugins are next. see post in the Meta board for details

Pages: 1 ... 8 9 [10]
 91 
 on: November 10, 2019, 12:26:59 pm 
Started by patrick - Last post by rayarachelian
David posted an updated trailer here: https://www.youtube.com/watch?v=Zlll7x2td9Q

 92 
 on: November 09, 2019, 05:10:07 pm 
Started by AlexTheCat123 - Last post by rayarachelian
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.

 93 
 on: November 09, 2019, 04:28:24 pm 
Started by AlexTheCat123 - Last post by AlexTheCat123
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?

 94 
 on: November 08, 2019, 04:22:36 pm 
Started by Lisa2 - Last post by Lisa2
This is a warning to folks that may have a Lisa in storage or are considering a purchase of Lisa.

The earlier versions of the Lisa (Lisa 1, Lisa 2/5) had internal NiCad battery packs that leak and cause serious damage.  Read more about this here:

https://lisafaq.sunder.net/lisafaq-hw-io_batteries.html

It is easy to identify the potentially troublesome systems by counting the number of 25 Pin connectors on the back of the system. The effected systems have 3 of the these DB25 ports in a horizontal row.  If the system has only 2 DB25 ports then the system does not have batteries.

If your system does (or did) have batteries, and they were not removed over 25 years ago there is a high likelihood that the system has sustained battery damage.   If you still wish to buy one of these Lisa's today, be aware this has been a chronic issue for over 20 years now and the supply of inexpensive spares for the commonly damaged parts is long gone.  Because of the this, it can be very expensive and time consuming to restore or repair one of these systems if they have battery damage.   

Rick



 95 
 on: November 07, 2019, 12:14:33 pm 
Started by AlexTheCat123 - Last post by Lisa2
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

 96 
 on: November 07, 2019, 08:28:04 am 
Started by AlexTheCat123 - Last post by AlexTheCat123
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.

 97 
 on: November 07, 2019, 06:19:17 am 
Started by AlexTheCat123 - Last post by rayarachelian
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.

 98 
 on: November 06, 2019, 01:27:56 pm 
Started by AlexTheCat123 - Last post by AlexTheCat123
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?

 99 
 on: November 05, 2019, 08:42:12 pm 
Started by AlexTheCat123 - Last post by rayarachelian
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.

 100 
 on: November 05, 2019, 07:16:40 pm 
Started by AlexTheCat123 - Last post by AlexTheCat123
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?

Pages: 1 ... 8 9 [10]