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Mac Goodies at Silicon Valley Electronics Flea Market
Posted by: bigmessowires on 2016-06-11 12:20:43 Today was the monthly electronics flea market at De Anza College in Cupertino: http://www.electronicsfleamarket.com/ There's often a bit of old Apple stuff there, but today was exceptional. There were several different vendors with ImageWriters, LaserWriters, keyboards, disk drives, power supplies, and of course Macs. We saw lots of old iMacs, a 20th Anniversary Edition Mac, a Performa 6000-something, Powerbooks, and more. I bought an Imagewriter II for 75 cents, but my friend and I managed to resist the temptations of the other Apple hardware. At least we did, until... One of the last vendors we visited had PILES of vintage Mac stuff. He probably had 20 assorted Plus and SE systems, along with a IIci, IIcx, IIx, LC, a Duo, and more that I lost track of. Tons of this stuff! He also had lots of keyboards, a box of about 100 double-density floppies, spare analog boards, random accessory cards, and spare logic boards. He didn't seem too familiar with what he was selling, so I think he must have bought the whole Mac lot from another collector. In the pile of logic boards, my friend and I found a few gems (or what we hope are gems). We bought three logic boards for $50 total. The first is an extremely clean and beautiful looking specimen. I'm not 100% certain, but I think it's an original Mac 128K board. The logo on the RAM is one I haven't seen before, though, so it may have been upgraded to 512K RAM at some point. What do you guys think? When powered up, it chimes but then displays a Sad Mac with code 020800. Here's a photo of the board, and close-up of the RAM: The second board is a little bit grimier, but still pretty good. I thought it was a Mac 512K logic board, but it seems to be a 512Ke, because it was able to boot from my HD20. Maybe somebody swapped in the newer ROMs at some point? The board has two boxes for checking off 128K or 512K, which I thought meant it was a Mac 512K and not 512Ke. Anyway, it works fine. Photo: The third board is the one my friend grabbed. I think it's a Mac 128K logic board, but probably one that's been upgraded to 512K RAM. It has a tiny daughterboard next to the CPU. Has anyone seen something like that before, and have a guess what it is? He hasn't booted it up yet. Here's a photo:
Posted by: TheWhiteFalcon on 2016-06-11 12:40:54 Unless my 128k has been upgraded as well(and I don't believe it has), the top board is all original.
Posted by: unity on 2016-06-11 12:54:14 Yup, first is original. Your friends is an original with upgraded RAM. Nice finds!!!
Posted by: Gorgonops on 2016-06-11 12:54:47 Unless my 128k has been upgraded as well(and I don't believe it has), the top board is all original. 4264 is Micron's model number for 64kx1 DRAMs (why they didn't use the more common 4164 labeling I'm not at all sure off the top of my head) so, yeah, that's 128k right there.
Posted by: bigmessowires on 2016-06-11 14:13:26 Awesome, thanks. For the original 128K board, I could try to repair it. The Sad Mac code indicates the RAM chip at G8 is bad. But I'm thinking that an all-original 128K logic board is more special than a repaired 128K logic board, even if it doesn't work. What do you guys think - am I crazy?
Posted by: Bunsen on 2016-06-11 14:34:53 No more so than anyone else here 😉
Posted by: wthww on 2016-06-11 14:35:54 I feel like it is a sort of sacrilege, but that original 128k board would make a wonderful art piece unrepaired. I'd probably frame it or something along those lines. //wthww
Posted by: TheWhiteFalcon on 2016-06-11 14:36:59 I haven't fixed mine, but I have a Plus with the 128/512k faceplate so I can cheat for demonstrations of "the original Mac". 🙂
Posted by: LazarusNine on 2016-06-11 16:13:41 Brilliant find there! As far as your question goes, my inclination would be to fix it, given that I've got the 'things must operate bug'. But then...it's a 128k board. It's not necessarily going to be used much anyway. Sooo...maybe just leave it as it is - pure!
Posted by: rsolberg on 2016-06-11 16:14:09 The daughtercard on your friend's logic board is from Levco, but I don't recognise it.
Posted by: Bunsen on 2016-06-12 15:43:23 Could we get the numbers off that TI chip on the daughterboard? I can't quite make them out. I wanna say it looks like a shift register, but that's a very wild guess.
Posted by: Bunsen on 2016-06-12 15:44:45 that original 128k board would make a wonderful art piece unrepaired. I'd probably frame it Put it on the wall behind glass and wired up to power, AB+CRT, mouse/kb etc.
Posted by: rsolberg on 2016-06-12 18:49:25 I see 535XI SM74AL5253H
Posted by: mooseman on 2016-06-12 20:32:46 Hi guys, I'm the friend with the other board. Yeah, after I got it home I realized that all the RAM chips have very obviously been resoldered. I assume the daughtercard is there to address the additional RAM. The chip is a TI and says 535XI and SN74ALS253N There's also a very small two-pin IC next to it with Z(2)104Z5. I've got a 512K in the closet but haven't tested the board yet.
Posted by: rsolberg on 2016-06-12 22:53:00 A multiplexer! I wonder what it's doing there.
Posted by: bigmessowires on 2016-06-13 07:38:20 The Z(2)104Z5 is likely a capacitor and not an IC. This little board must have something to do with the increased RAM capacity, but I'm not quite sure how. This makes me wonder, for a 128K to 512K upgrade, how are the extra address lines connected to the RAM chips? Are they already present on the 128K logic board, even though they aren't used?
Posted by: unity on 2016-06-13 08:48:25 I have 128k boards that have been upgraded with similar small daughter cards. On the 512k hybrid board, Apple added it themselves pretty much. Keep in mind, the 128k board was designed for more RAM. Those unused vias you see where that small board attaches are no coincidence, a remnant of the "diagnostic port" that they claimed when confronted by Jobs.
Posted by: rsolberg on 2016-06-13 09:59:10 Ahh. I didn't realise additional ICs were needed to address the upgraded RAM on the original 128k boards. I thought it was perhaps used for an upgrade beyond 512k- I've seen something of the sort on a later 128/512 board with about 2MB total RAM.
Posted by: khannonnd on 2016-06-14 00:13:26 Is this Silicon Valley Electronics Flea Market something that is worth me -- an SF Bay area mac fan -- going to or is it kind of hit or miss? Those finds are pretty remarkable!
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