Since the transformer and regulator are energized as soon as you plug the meter in, 5.5V or so should appear across U26P2 to C23-negative even before turning the power switch on. You can check your work this way without possibly damaging the rest of the meter if you make any mistakes.
I am having an issue with the mod. I performed the steps that you listed, although my PCB was slightly different than the picture provided. When cutting the trace that connects to U26.1, I had multiple traces (3) ending at U26.1 besides the battery pack. These multiple connections was the transformer, T3, C22, and C34. The cut disconnected those components from U26.1. I take it this is correct, no?
Also, after adding the 510 ohm resistor from C23 (negative pin) to U26.1 and plugged in the power cord (after all other steps were performed), I only got a voltage of 4.5V when probing U26.1 and C23 (negative pin), so I ended up upping the resistance to ~650ish ohms to get 5.5V. At this point, I turned it on and nothing appeared on the LCD.
I checked my work a few times and I'm fairly certain I did the steps correctly. When I checked the voltages at TP2, 3, 4, and 5, I don't get the voltages as described in the schematic. I was checking these voltages when having one probe placed on C23 (negative pin) and the other on the test points. The voltages observed were roughly 6V (6.5V on some). But then I thought that I may be placing my other probe, (that connects to C23 negative pin) incorrectly so I placed in on the front panel common plug and the voltages on the test points were in the mV range.
I don't know if any of what I said provides any insight as to what I did wrong, but any advise would be appreciated.
I'll have another crack at it in the morning.