curiousmarc
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(Spoiler Alert) Good job Patreons on guessing the PS/2 fault
🕑 Added 2021-11-02 23:18:32 +0000 UTCHere are the results of the poll:
And you guys did pretty good, much better than the average commenter that thought it was a cap. Well the average commenter *always* tells me it's a cap, no matter how much I show and explain what the fault actually is in the video.
As you can see, the most popular Patreon guess was a broken trace in the PCB. It's very close but no cigar. The second guess was a bad via. Turns out, bad via is the correct answer.
That's what Eric's magic finger was inadvertently pressing on, as a side effect of putting pressure on the side of the chip in his special magic way. Eric had the hell of a tough time finding it though. He tested every single via with the scope probe in the area, while is custom BIOS was making beeps through the IO chip. When putting the scope probe on one particular via, the beep started to crackle. It was indicating the BIOS was temporarily losing access to the chip. Intermittent via.
And even knowing exactly where it was, and looking under the microscope, we could not really see it. It's the top row, second via from left. Maybe there is a suspect crack line inside, but many of the other vias looked the same.
Eric put a thin wire through it and reflowed solder, and it worked reliably again. Makes you wonder how many other potentially bad vias are about to fail.
And thanks to viewer Clinton Moody, we got one of the original IBM CD ROM players, complete with the matching IBM blue eject button! Eric added it to the now-fixed computer. Thanks a bunch Clinton!
And Clinton also sent us a copy of the OS/2 Warp 4 CD and the 3 startup diskettes in his care package! Eric installed it, but it overwhelms our 250 MB SCSI disk and the poor 486 processor. We'll probably downgrade to the OS/2 Warp 3, which would be a better match for this machine, and which we have in diskette form, proudly sitting on top of the computer in the picture.
Marc
Comments
CuriousMarc
Yeah, close enough, you’ll get 2x your bet then.
Isn't a via just a bit of track that goes through the board ;-)
I had bad bias issues in the past! Congrats, they are really difficult to debug
