Quoted from barakandl:I don't think you need to go out of your way to change the 100k resistors in the digit drive to 1/2w. In my XP they only fail when there is some other problem that makes them fail, like a locked digit driver.
For the OP issue with missing segment.... Replace segment 'f' driver at Q18. Still no go, replace the 7 segment decoder IC 4543. Still no go, follow the segment circuit up to where it goes into the glass. Compare to other segments in display test with DMM. If good there, the display is bad itself.
I had a very similar issue to the OP and I did end up finding a bridged solder point where the display segment solders on to the display board. Fixed up the bridge and plugged display back in and now working MINT! This was a lot of help. Thanks guys.