Well, i would find a way the check the strobe first!!!
You are assuming the strobe is 100% accurate. It may be what is wrong!
If you get a stopwatch and carefully count the platter turns for exactly 3 minutes and see if it is 100 rotations... 33 and 1/3 for three minutes is exactly 100 rotations. Then if you are way off on speed like you assume, the number will be short of 100. THEN get worried.
If it is right on, (or within a quarter turn or so) then your strobe is messed up. (You could even use a cheap clock, but a longer test would be better with a less accurate device, say 200 turns in six minutes..)
So i would find out if the strobe is messed up first.
You could also take the strobe to a friends place and check it.
If your table sounds in pitch, i would think it is the strobe that is off.
You are assuming the strobe is 100% accurate. It may be what is wrong!
If you get a stopwatch and carefully count the platter turns for exactly 3 minutes and see if it is 100 rotations... 33 and 1/3 for three minutes is exactly 100 rotations. Then if you are way off on speed like you assume, the number will be short of 100. THEN get worried.
If it is right on, (or within a quarter turn or so) then your strobe is messed up. (You could even use a cheap clock, but a longer test would be better with a less accurate device, say 200 turns in six minutes..)
So i would find out if the strobe is messed up first.
You could also take the strobe to a friends place and check it.
If your table sounds in pitch, i would think it is the strobe that is off.