LisaList2
General Category => LisaList2 => Topic started by: ried on August 04, 2024, 09:27:21 pm
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I recently picked up an early Parallel expansion card which seems to be from 1982 and differs significantly from other cards that I have. The earlier card has plastic parallel ports and is part number 820-4017-A, while the later card features the usual metal ports and is part number 820-4027-A. Notably, the early card also lacks the FCC ID, which is usually present and covered with green paint on later cards and subsequent versions.
Anyone else have one like this? Gallery: https://imgur.com/gallery/apple-lisa-parallel-cards-profile-9zsk8ZP
(https://i.imgur.com/WdYnQEd.jpg)
(https://i.imgur.com/CboMBdP.jpg)
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I've never seen anything like that before! I wonder if it's some sort of prototype?
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Could be. The part number 820-4017-A does not seem to show up in Google search results.
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I can't spot any difference. If you have one, stick the cards in a flatbed scanner and superimpose the scans; toggle/fade layers and see if you spot a difference. Could just be down to a trace or two.
ROM contents probably differ; use BLU or a programmer to read them out and compare.
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The only difference that stands out to me (other than the obvious P/N changes and DB differences) is that the early board appears to be a two layer board, while the production board is a 4-layer with inner ground or voltage planes.
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There also seems to be a slight difference in the solder mask on the gold fingers of the slot connector. The rounded tops of each finger aren't covered in solder mask on the "regular" version of the card, but they are on this earlier version. And the horizontal traces coming off pins 55 and 56 of the connector are briefly exposed in gold on the regular version, but are covered in solder mask here as well.
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The logos of the PCB manufacturers (left side on the reverse) are different, too.
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It is an interesting find and board members did a great job pointing out the differences between the two. Having serviced a number of these machines back in the day, I can say the occasional inconsistency would pop up. When I asked techs at the time about it, they brushed it off stating Apple used what they had in stock and all that mattered was that it worked for the task. My guess is there will be other nuggets popping up that have been overlooked in the past. Anyway, that's my 25 cents.
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Ralph, very nice to see you on here! Thank you for the anecdote, and the parallel card 8) I hope you'll continue sharing your insights about these special machines with the fine folks here.
Welcome!
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I've got a super early, single port card... I think from a prototype system that didn't have the onboard parallel port. I've posted photos of it: https://lisalist2.com/index.php/topic,97.0.html
-J