I have obtained a beautiful IBM ThinkPad 560. Unfortunately, there are no signs of life when power is applied. However, it's in such lovely shape that I have no choice but to repair this.
Unfortunately, all that effort to replace the soldered CMOS battery based on a reddit comment were for naught. Will begin investigating the power supply situation from the 16V barrel jack on.
I've verified all six fuses I could find on the board, and they all function properly.
I have placed an order with Digi-Key for some replacement Rubycon capacitors for the DC-DC board. The fact that DC-DC boards are going on eBay for more than I paid for this whole machine is very telling that this is a frequent point of failure. The fact that the capacitors are rated awfully close to their operating voltages is also suspicious.
Resorting to more extreme measures, I'm pulling the piss tapes and the tree saps out of the archives. That's right. Kapton tape, flux, and hot air, to see if a reflow will fix anything. (Seriously the Kapton tape smells like...pungent)
The reflow did not fix my issue. However, I did narrow things down to definitely the DC-DC board itself: When it is plugged in, I observe ~0.3V in places where I would expect 3V3 or 5V. Without the board plugged in, I observe no current. Therefore I will try replacing the MAX-series chips on the DC-DC converter:
@retrotechtom I wish I had the facilities to properly disassemble the panel to do some investigation (it appears to be a common failure mode on this panel). I'll maybe keep this one around after I get a replacement, one hopefully I don't end up spending more than I have spent on the machine originally...
@gizmomathboy Oh it's not a huge deal! Just gotta use Kapton tape to protect the surrounding areas, and hit each chip with the hot air gun until it moves out of the way. Soldering the replacements is just being steady and checking your work.
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