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Top-level
 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! 140 comments
[DATA EXPUNGED]
 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 The single strip of Scotch tape in the middle is a nice touch.  @tubetime Did you have to make your own contacts of could you reuse something else? @tubetime Perhaps the Hirose DXM connector? https://www.mouser.com/new/hirose/hirose-dxm-connectors/ @maehem yeah i sorta think its a Hirose product but it's not DXM, which has only 2 rows of contacts, not 4.  @tubetime Here's the 0.8mm pitch version.  @tubetime and apparently that specific one is only found on 700 and 720 series. Probably this one is ISA only, whereas the following series have PCI and/or CardBus.  @tubetime looks like some kind of mezzanine connector last night i reverse engineered it. the design is simple so it wasn't too hard. the files are here: https://github.com/schlae/Thinkpad700CPower it also explains the mystery "INPUT SIGNAL" pin on the old 4-pin IBM Thinkpad power connector. this pin simply increases the output current limit when it is pulled low by the laptop. it's because the power brick is also the battery charger, and when the laptop is turned on, you have to increase the current to compensate.  @tubetime You're taking good care of the capacitors they're growing in size! 😆 @tubetime Now that would be a truly useful AI - upload a picture of a connector (perhaps with a ruler for scale), and it tells you what the connector is and where to get it. Yours was a tough one, but its hard even for more common connectors. Next time I go to Anchor I’m going to take some stuff with me to see if I can find matching connectors. @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. |
Gregory's Server
want to stare at the schematic yourself? i've put it on GitHub. https://github.com/schlae/Thinkpad700CPower