I started with the usual, leave it on and see if the LCD comes on, use a heat gun, etc, no changes in behavior were observed. So, since these are all old caps that probably need replacing anyway, I've recapped most of logic board (I haven't touched any of the 1uF's, 3 radial 100uF's, and a single 4.7uF, I need to order replacements), including C22 which...{snip} is known to cause problems with the lcd bias voltage.

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Try measuring the voltage across the cap to see if you are getting the -21V bias. You should see this voltage at one of the connector pins as well. If you don't see it, that's your problem, and C22 is a likely culprit.

I recall DigiKey having suitable replacements. But before bothering to hunt down parts, just make a couple of measurements to see if that's even necessary. And also be sure to perform the standard "pull out the flex cable, reinsert the flex cable" ritual a couple of times to see if that fixes anything.

Good luck!