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Author Topic: The Great Extendo  (Read 476 times)

stepleton

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The Great Extendo
« on: August 06, 2020, 07:03:50 pm »

These AppleNet cards are making a monkey out of me. I'm gonna need to probe them, but it's hard to reach them inside the Lisa when they are installed.

Does anyone have any physical specifications or measurements for Lisa expansion cards?

I'm thinking it might be nice to make some kind of bus extender. I would be shocked if you could still get those ZIF expansion slots from anywhere, but maybe it's possible to hack an ordinary card-edge connector to receive a Lisa expansion card. Anyway, the idea would be to feed the bus lines just a short way outside the case via ribbon cable---that way I can poke the card with a scope. I'm not sure how much the bus will tolerate this, but it's not too much of a hassle to give it a shot.

Speaking of things around the expansion connector, has anyone got a source for those wide-slot screws that the rear panel uses to hold in the expansion slot cover plates? I'm missing one.
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rayarachelian

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Re: The Great Extendo
« Reply #1 on: August 07, 2020, 09:28:13 am »

The specs are in the Lisa Hardware Guide for the size of the cards, etc. don't have that handy now, but check bitsavers
I think the pins are the same spacing as IBM PC ISA slots, so if you can find a connector for an 8 bit ISA slot - the short ones, you might e be able to use that, though youll need to cut the back end so the card can slide into it as the lisa card is much longer and expects to slide in as those zif sockets are pretty unobtainum.

I don't know if isa slots are still available, but I'd guess they're a lot more available than lisa ones. worst case you've got a lot desoldering to do to reclaim one off a dead motehrboard.

(still no electricity)
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patrick

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Re: The Great Extendo
« Reply #2 on: August 07, 2020, 03:10:34 pm »

Does anyone have any physical specifications or measurements for Lisa expansion cards?

Attached is a template for the Lisa Expansion card in Eagle 2.60 and 5.12 format. KiCAD should be able to import this.

Some 20 years ago I made my own SCSI card for MacWorks. Based on the SunRem circuit, two-layer PCB etched in the kitchen, all components soldered from both sides, no plated slot -- but it worked! A few years later it got replaced by a genuine SunRem board after a couple of unpopulated bareboards appeared at ebay.
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stepleton

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Re: The Great Extendo
« Reply #3 on: August 07, 2020, 05:52:28 pm »

Fantastic! Thanks Patrick!

Guess this means I've got to go ahead and try to make one of these things  :D
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patrick

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Re: The Great Extendo
« Reply #4 on: August 08, 2020, 07:25:19 am »

How do you want to arrange the board unter test on the extender? 90° rotated, so that it points out backwards?

Provide a breakout point (pinheader with jumpers) on each signal line, and one test pin for the logic analyzer. Or better two, one before and one after the break. And many Gnd connections. Power lines might be protected with PTC (self-restoring) fuses and fitted with indicator LEDs.
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stepleton

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Re: The Great Extendo
« Reply #5 on: August 08, 2020, 12:31:08 pm »

I was thinking to have a pin header on the expansion card and then a short ribbon cable going to a small separate board with a socket for the card and pins for probing. My home setup doesn't have a lot of room, so having the card be able to flop around a bit could be helpful.

It might be a good idea to have a switch on the +5V standby power line, and maybe another that can bridge \BGOn to \BGOn-1.

Maybe I'll sketch a design and put it up for critique before I have any boards spun. In any case, I will probably keep on disassembling for a while before I pursue this in earnest.
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patrick

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Re: The Great Extendo
« Reply #6 on: August 09, 2020, 02:28:26 pm »

I was thinking to have a pin header on the expansion card and then a short ribbon cable going to a small separate board with a socket for the card and pins for probing. My home setup doesn't have a lot of room, so having the card be able to flop around a bit could be helpful.

My temporary solution was an edge connector cut from an ISA card soldered to 30 cm flat cable, and an ISA socket at the other end. Did not look very reliable, but worked quite well.

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stepleton

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Re: The Great Extendo
« Reply #7 on: August 09, 2020, 05:48:49 pm »

30cm is encouraging! I was concerned that more than a few cm would upset the bus somehow. I'm no EE; all I can do is be superstitious and try making big margins...
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stepleton

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Re: The Great Extendo
« Reply #8 on: August 15, 2020, 08:04:11 am »

Starting to have a look at making this bus extender.

Patrick, it looks like KiCad can only read Eagle 6+ XML-based files and not the older binary formats. "pcb-rnd" is a FOSS program that can read the "512" file, but not well. Is there any chance that you have the ability to make a file in the new XML-based format? I know EAGLE licensing got increasingly antagonistic as the project evolved, so I won't be surprised if you don't.
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patrick

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Re: The Great Extendo
« Reply #9 on: August 15, 2020, 09:35:55 am »

Please try the file attached. I do not own a license for Eagle 6 and the freeware version only works up to 80x100 mm2, but it seems I can open the file and save it in XML format.


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rayarachelian

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Re: The Great Extendo
« Reply #10 on: August 15, 2020, 12:12:50 pm »

These might be useful in the conversion (but require you to have eagle, I think): https://github.com/lachlanA/eagle-to-kicad - there's also a link to a video, found it via HackADay: https://hackaday.com/2015/12/27/eagle-to-kicad-made-easy/
I don't know much about Eagle, sorry, if they're helpful great, if not, pls ignore.
« Last Edit: August 15, 2020, 12:17:02 pm by rayarachelian »
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stepleton

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Re: The Great Extendo
« Reply #11 on: August 16, 2020, 08:46:14 pm »

Thanks Patrick! The new file imports just fine. Rather than adopt the board outline directly, I decided to use it as a template in order to figure out how KiCad does card-edge connectors. After an afternoon, I think I've succeeded in making something that works in the official KiCad way, but I don't think it really bought me very much :)

More as things develop...
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stepleton

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Re: The Great Extendo
« Reply #12 on: August 22, 2020, 05:51:36 pm »

Here's what the bus extender looks like so far. KiCad has 3D models for some components but not others.

You clip out the panelised board within the expansion card and attach it on the other end of your ribbon cable. Then you plug the expansion card that you want to probe into that. I haven't figured out what keeps your expansion card from tipping over onto its side, but maybe it doesn't matter.

Unfortunately I think I will need to move the ribbon cable connector on the expansion card down a few mm...
« Last Edit: August 22, 2020, 05:58:53 pm by stepleton »
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stepleton

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Re: The Great Extendo
« Reply #13 on: August 22, 2020, 05:52:51 pm »

Here's a detail of the "coupon":
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rayarachelian

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Re: The Great Extendo
« Reply #14 on: August 22, 2020, 06:10:02 pm »

Very neat! Have you found a source of compatible edge connectors to use? I looked around and the new places that advertised ISA card edge connectors no longer had them.
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