Gregory's ServerI'll need to figure out how to fix the hinge mounts. they were very weak in the original design, and the hinges stiffened up, so when someone opened it up, the plastic just shattered.
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178 comments
  @tubetime Problems solved by whacking with hammer: *adds one to the tally*  @tubetime I'm not sure, but I think your sheet size is a tad bit too small for your schematic
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@tubetime Huh? On a power supply board? What sub-circuit are these resistors part of? @attilakinali there are 7 of them. they trim the output voltages and a few other parameters @tubetime interesting. I would have thought that 1% resistors would do the job for the voltage feedback of something like a computer. Any idea why they need this level of accuracy? @attilakinali 1% is indeed fine for this. but they probably thought doing it this way was some sort of competitive advantage lol  ok i have a theory about why this was failing. symptoms: randomly the computer would shut off and pull a ton of current... 1) crowbar circuit fires. it can fire due to a rail going overvoltage... 2) a buck converter's MOSFET wasn't switching properly... 3) oh look this diode wasn't connected anymore due to a bad via! want to stare at the schematic yourself? i've put it on GitHub. https://github.com/schlae/Thinkpad700CPower
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 I just checked and (thankfully) CHM doesn't have one. They actually have almost no ThinkPads in the collection. I have nightmares about how many early 90s machines in the collection have pcb rot. @tubetime I had totally forgotten about active vs passive matrix displays! The minute I saw an IBM active matrix LCD, I knew the end was nigh for the CRT. It was amazing for its time. @tubetime Active matrix, man. A million psychedelic colors... I bet it looks crispy in the dark.  @tubetime Others have speculated in the past that IBM used Nextel Suede coating. https://www.nextel-coating.com/produkt/nextel-suede-coating-3101-90fh-11-black/?lang=en&v=3a52f3c22ed6. I am not sure if that info is correct. Difficult to get in the USA and $$$. I know folks who may have very limited quantities (used on aircraft instrument panels), may be the wrong color or variant.  @jonhendry by shining a flashlight through the board and looking at the shadow of the trace. if it is more distant or fuzzy, then it's on the opposite side of the aluminum core  @tubetime I'm guessing they trimmed to tune the system as a whole, not just the single resistor value? @tubetime My first job out of school was doing fpga stuff at a company that did laser trimming. It was wild. They used analog circuits to drive the galvos which had the mirrors. If the circuitry was off by a bit, you could see the “ringing” of the circuits in the right angle cuts (instead of an angle you’d see a little degrading sine wave). I’m still convinced analog EE’s are wizards.  @tubetime the one and only time I soldered directly to a coin cell it exploded in my face. Never again! @tubetime You need a small spot welder in your arsenal (and so do I) @tubetime I’m too scared to do that, so I use electrical tape to tape the wires to the cell (plus cover the whole thing with said tape so it looks similar to the original)  @tubetime You can just use a regular soldering iron for this and for the small parts you'll need a finer mesh, can find it on amazon https://www.amazon.com/dp/B0B3T3ZBSR . Holds much better than the glue |
i also need to figure out how to fix the error codes, but that should be simple.
00016100 - CMOS battery
00016300 - Time and date
I9990303 - System boot partition failure (I pulled the HD)