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@systems_glitch
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Embedded, industrial, and scientific electronics and apparatus. Hobbyist kits largely for vintage computers.
Joined July 2014
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Ordered some business card size CD-Rs and what came is actually rectangular! Never seen these before. They have a cut that allows them to center in the standard 8cm depression in a CD tray.
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“But where will you get repair parts from? Not from stealing off other boards…right?”
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Getting the Data General NOVA 4 ready to head to its new home!
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You know you're at a semiconductor fab when the toilet supply is Swagelok fittings and formed stainless hard line.
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On the bench today, a Voodoo 5! This one shits the PSU down.
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Remember when it *wasn't* integrated on the microcontroller?
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Thanks to supply issues, this is now the "cheap way," *by* *far* to get non-fake 28C256 type EEPROMs. Good thing we have a pick and place line?
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Another Altair back in operation! First pictures are how it arrived. Completely stripped down, nearly every fastener removed, cleaned, sheet metal reworked, electrically repaired, and reassembled. MITS 16K SRAM card instead of IMSAI 4K SRAMs.
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"Hey can you guys fix a LED sign?"
"Yeah probably bring it by the shop."
This morning:
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Wonder if anyone at MITS ever thought you'd be able to run an Altair 8800 with 64K of memory (RAM+ROM) and MITS 8" disk system in just three boards?! The CPU and serial interface are vintage, the third board is Mike Douglas'/DeRamp FDC+
Excuse the mess.
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Honestly a better way to acquire cheap parts than the last video...
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Here is the fix, before getting sealed and insulated:
Fuses are good, so I started searching for damage, and found this small scratch on the bottom near the ports:
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All laid out:
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Encapsulated in two-part epoxy after cleaning and retest! Board is back in operation, probably going to get maxed out on texture RAM.
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Until it passes the Rasmussen memory test, for hours, with zero errors, your RAM boards are not "tested," "fixed," or "working."
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Cobalt Qube 2 finally reassembled and back online! Visit it at and/or visit us on IRC at
#cobalt
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This is also the origin of the term B+ in tube circuits, to refer to the main high voltage supply used on tube plates!
"A" voltages were used for filaments, and "C" voltages were used for grid bias, until self-biasing became the common practice.
There are AAAA, AAA, AA, C and D batteries but what about B type batteries?
Meet the vacuum tube era 45 volt B type battery.
They are still manufactured.
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“But why do you bulk replace surface mount electrolytic capacitors on boards that work?!”
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Wanted a Live! Drive for decades, finally got o e for less than the rest of the computer :P Not the FireWire model, but that’s OK.
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This one time I found a KIM-1 in an employer's warehouse. Then I found a box with five more. Story and pictures:
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On the bench today: a Voodoo 3 that belongs to
@geekenspiel
!
@vswitchzero
already took a look at it and determined it needs BGA work. We will start with a reflow:
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Scrap lot is in! I had to immediately test that Voodoo 3 3500 TV…AND IT LIVES!
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“The saddest lot of 3dfx cards on eBay” — except one was a RIVA TnT :P
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Repaired and working Lisa 2/5 with 5 MB ProFile:
Everything repaired, there was battery leakage but it was relatively minimal, mouse is an early Macintosh model.
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This is the tower that Socket 7 AMD K6 had been living in. With the two digit speed readout, I feel like this really should house a 486, maybe Am386DX. Thoughts?
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Siig MiniSys S286 with a little 9" point of sale monitor and Siig MiniTouch keyboard. Repair writeup here:
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I came across this old nemesis again this evening…BUT HAVE NOW IDENTIFIED IT! It is an Alaris Leopard rev C 486SLC2 motherboard! I have had it since the late 90s or so and it has never worked due to missing BIOS.
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Thanks to a whole bunch of vintage computer folks, the Sun 3/50 now has an ECL monitor!
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Ever wonder where cheap parts come from?
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Zephyrtronics ZT-7 BGA rework station is in! Works excellent, real game changer!
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Last weekend, we did some work on an Ohio Scientific CD-23 disk system, which uses a Shugart SA-4008 14" hard drive, at the System Source repair workshop:
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Hey, I found all the missing Diamond Voodoo 1 and 2 PCI slot brackets!
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Progress! Message printed using RSC-FORTH V1.7. Display dimming working, too.
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Have some? They have their own drawer! (Harris/Intersil licensed 555 in a can)
A thread about neat 555 facts and stories. Doing some research in the 555 timer. Did you know that the 555 timer was originally released in both a standard DIP-8 package along with a metal can package? Does anyone have one of these? 🧵🪡
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Well now we know why that Voodoo 3 2000 was intermittent and reflowing didn’t help :/
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All the 486s from the quoted post, plus a few from around the shop, have been cleaned and tested: all work!
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Starting to accumulate a number of 3dfx chips that need reballed…
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"The front panel flashed out its warning: 'you popped the stack before returning,' and the data, like silent raindrops fell"
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Systron Donner 7004A multimeter with Nixie displays fixed! Bad electrolytic in the display update/refresh oscillator. Full picture thread here:
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Well, we finally built up that original Ohio Scientific 400 board...but for the Motorola 6800, not the 6502. Why in the world would anyone ever do that?!
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Altair 8800B burn-in! Found two cracked traces on the motherboard. It's now booting CP/M with some additional test set boards and is running the Lifeboat Associates Rasmussen memory test. Found another intermittent SEMI4200!
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Another Altair 8800B finished up and in burn-in! This one is configured with 48K of MITS 16K SRAM, a SSM IO-4 set up to be a MITS 88-2SIO, Processor Tech 3P+S set up to be a MITS 88-SIOB for 88-ACR support, and a reproduction SSM T-1 terminator.
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Early National Semiconductor DM8200D 4-bit magnitude comparator. This one is in a ceramic "gold sandwich" carrier, the pins are actually rolled instead of just stamped/coined. Tested in a breadboard, still works! Assuming 6831 is "31st week of 1968."
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Sometimes the test gear needs fixing! Tantalum capacitor blew up on the Landmark KickStart 2.
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Click-clack! Orchid Righteous 3D (Voodoo 1). Nonworking of course. Some damage to the PCB near the top, and some loose pins on the TMU.
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Found my first FIC VA-503+…and not only does it still work, it somehow still has a good CMOS battery and the right date! Time drifted 3+ hours though :P
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I've been assured this device does not exist, much less as an official
@Apple
product. It's an AAUI to AUI converter, with a built-in power supply to provide 12V.
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This Socket 7 board is almost pristine! There is a broken SIMM socket latch, and the DS12887 needs replaced.
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Some of the Slot 1 stuff! This isn’t all of them, there’s another box hiding…
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Another Altair 8800B fixed! This is my personal system, it started out as a 8800B Turnkey from
@billdeg
but I found the front panel circuit board all by itself from a local scrap guy in Troy, years ago. The inner panel is the same between them.
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New caps in the ABit KA7 Slot A board! It POSTs but I have no PS/2 keyboard.
Cap goop all over this Slot A Athlon board! Almost every cap was leaking, even the ones that don’t need to be low ESR.
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Finally did a writeup on repairing and upgrading the HP 5326B Timer/Counter/DVM with Nixies:
This one had a factory wiring error that wasn't exposed until an upgrade ovenized timebase was installed! Still a useful instrument.
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Before and after: a very nasty Altair 8800B now fully functional!
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It's 2023 and two days ago I installed a new thinnet/10base2 Ethernet segment for a machine that's critical to a big company's manufacturing operations!
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Progress! Currently running with a wait loop multiplex routine, but it pulls ASCII char data from a buffer, looks it up in a character generator, and places it in the pixel framebuffer!
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This board is out of a Fairchild Model 7000 DMM I used to have. Unfortunately, when it was in storage at a friend's business, one of his employees decided to start scrapping any "old stuff" he could find, and the Model 7000 got cut up. I did manage to save this board.
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Finally, a high-end 486 motherboard working! FIC 486-PIO3. Voltage regulator section required repair, now running an
@AMD
Am5x86-P75. This board is getting used to test all the 486s from that box of CPUs.
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Another MITS Disk System 8" drive back in service! This one got the PSU fully replaced, buffer board repaired/modification removed, spindle motor disassembled and fixed, door closed switch aligned, and a full drive alignment.
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FINALLY! The exact model of AT desktop case I’ve been looking for! There are a zillion variants of this case, but this one is superior.
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Another Voodoo 1 on the bench! This one is a revision A Diamond board. Looks like it took a hard hit: there is some PCB damage and a mushed electrolytic cap, plus the usual loose pins on the TMU.
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Finally moving shelving from the shop/home office at the house to the building. Now most of the Altair and Ohio Scientific stuff is in one place!
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Testing approximately 300 Soviet clones of the Intel 8224 clock generator today...
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Sure is great we can get cheap high quality polymer capacitors for positions like these. Pretty sure being under a Slot A Athlon heatsink killed the old ones! One was an old OS-CON hybrid polymer.
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There we go, random Zip stuff around the shop corralled, tested, and put in the same place!
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It has been a while (2013!) but the Teletype Model 33 ASR is back online! I put one of David Tumey's new-made hammer heads on it today. Must've done a good job cleaning and lubricating it in 2013, punch and reader are both still fine, too.
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Not only is PICMG Slot 1 Pentium II a thing…you also get an onboard SoundBlaster!
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Fixing up an old MITS 88-SIO rev 1. This one is to be the system console. The B suffix usually means TTL levels, but someone had modified this one with two optocouplers and transistors long ago, probably for current loop. Redid it with transistor RS-232 shifters.
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Finally about wrapped up on this customer repair, a Sontec 250A. New PSU, new HS-1000 amps, fixed a number of issues in the right channel.
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Found it! I was pretty sure I still had a Diamond Monster Sound board from when these were current stuff. This is the M80 (stereo only) with a cut down DB.
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Today, in fact!
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