I've repaired my power supply and floppy issues, suggestions on cleanup?

From: Ray Arachelian <ray_at_email.domain.hidden>
Date: Mon, 12 Dec 2005 12:03:09 -0500

I was able to get this Lisa working.

I replaced several large caps in both the 1.2A and 1.8A power supply and got the Lisa to work from both.

The 1.8A supply had that large bulged out capacitor, it also had another identical one right next to it that had bubbled out - this wasn't visible until I removed both caps as it was inbetween them. The 1.2A actually had a small cracked capacitor that was visibly damaged. Replacing the caps helped.

There are more capacitors I'd like to swap out of both supplies, these are the large clear amber ones - they look like they've suffered some stress - there are small hairline line fractures visible there. One of the caps I need to do this is backordered, so I'll have to wait until the end of December to do so.

There was a short, but the short was from inserting the cable from the cable harness to the Lite adapter - the socket on the Lite adapter is keyed, but the plug on the harness is not, and from the way it fits, it looks correct when it's actually shorted. I suspect that perhaps the 1.8A was marginal, but working, but that the short caused by this is what prevented it from working. The 1.2A I knew was broken from before, and this fixed it.

So for those who need to know this: when there is a short the 1.8A supply behaves like this: power light comes on for 1 second, then shuts off, and you hear the speaker click once or twice. The 1.2A supply makes the speaker sound like a machine gun (or very fast clicking, like a sewing machine) when there's a short circuit.

After playing around with with the XL I/O board, I was unable to get it to see the floppy at all, *but* I was able to use one of the two battery leak damaged I/O boards. In fact, the one that had the parallel port 6522 with the plastic melted on it worked - sort of. I was able to boot using this I/O board, and while the mouse worked just fine, the keyboard did not.

After swapping out both 6522's and the COP421, I managed to get this I/O board fully working.

So this was a weirdo Lisa, it has a Lisa XL wire harness, but only 3 pin power, so it was never a Lisa XL, hence some of the confusion.

I do see a few other issues however. This Lisa has the "worm" problem - that is video wiggles very very slightly on the horizontal, so if you have a straight line, you can see a very small - perhaps no more than 1 pixel or even half a pixel wiggle. I recall the Larry Pina book mentioned this could be solved by switching from the 1.2A to a 1.8A power supply, but guess what, I am using the 1.8A supply! (It was doing this before the whole power/short issue.)

So either replacing the clear amber VAC capacitors in the power supply will fix the worms problem, or there's an issue with the analog video board. Anyone know how to address this?

I'll try to swap the 1.8A supply out tonight or tomorrow with a 1.2A supply and see if the worms go away, if they do, then I certainly need to replace the remaining caps in the 1.8A supply. But if they don't - then either the video board needs a bit of work, or both power supplies need their remaining caps replaced.

Battery leak cleanup questions

Also, what is the best way to clean the corrosion? Since these are alkaline leaks, James suggested that possibly using a distilled water and distilled vinegar might neutralize it, or perhaps using full strength vinegar and then some other alkaline stuff - like baking soda to catch the rest of the acid.

I can certainly reflow the solder at the joints that are green, and patch small wires between the traces that were effected, but how do I prevent the corrosion from spreading?

I'm a bit weary of using anything containing water, as I wouldn't want any capacitors soaking up the humidity and dying just from that, so I'm not sure - is it really safe to clean with water? I'm thinking maybe a lightly damp paper towel and some kind of brush - like an old toothbrush perhaps? Any suggestions?

The other non-working I/O board that also had battery damage which I cannibalized a 6522 from had one trace that was so badly corroded that it was visibly raised off the board by several millimeters: I can imagine this stuff eating through the copper traces quite easily, and since electricity is passing through those half corroded traces when the Lisa is on, they will heat it up, as more resistance builds up from the corrosion, the heat from the resistance will then act as a catalyst to further speed up the corrosion.

Also, I noticed that someone had repaired one of the boards and put some kind of clear lacquer on top of the repairs, where can I get this stuff from and what is it? Can it be used to seal repaired corroded portions?

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Received on 2005-12-12 09:09:44

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