I think you are right that it is Q1546. My A9 boards are not labeled, but the collector traces back to CR1541 and C1542, which is Q1546.
Does this scope have either option 4 or option 7? The board diagram in the SN>250K service manual (Fig. 8-18) indicates 3 possible capacitors with the note "2 Used only with Options 4 and 7". My boards have 3 pairs empty vias at that location, but look a little different than your picture in this regard.
I do have an empty via at the trace shown in your picture. The one that travels under the fuse to CR1569. The other via at that location - between the trace via and the R1549 via just to the right of the arrow tip - is not present on my boards. I'm looking at both a pre and post SN 250K boards. So I'm at a loss as to what that might have been. The trace is apparently the -8v rail, unless it's the ground side of CR1569, for what that's worth.
What is the SN range of this scope? Is it pre or post SN 250K? Any other options or indications of variation?
Sorry I'm not more help.