How can I fix the speed myself on a Steepletone ST918 record player ? 33rpm plays LP's at 45rpm !!!!

Check the videos as there is an adjustment. Also check for slipping belts.

https://www.google.com/search?q=Rockola+Sybaris+473+Jukebox+isn%27t+playing+at+the+right+speed

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Could be the belt for the pulleys is stretched a little, or there is something making it slip, or the potentiometers were set incorrectly from the factory . It is normal to have one for each speed. It is unknown if you can access these from the bottom of the unit. Slippage is less likely to be caused by something oily, since it would alternate the speed faster and slower and yours seems to have worked then reached a constant slower speed. Do your 45's and 78's play ok? (yeah I know, does anyone have a lot of 78's on hand)
Your model does not have an outside pitch control to fine tune the speed faster or slower. Another Jensen model JTA-230 does. Entry level turntables such as yours are not speed accurate reliable. After reading reviews on your turntable, it's possible that the belt is the problem. If the slow speed problem had happened from the start, it would be safe to say that the speed wasn't calibrated correctly and you could have returned it and perhaps had better luck with another one but because it worked fine at the start and then now plays slower, it's either the belt or the potentiometer for the 33rpm speed has somehow changed.

Do you have an audio digitizer device?

just buy a new unit if you ain't got friends to help you.... and45.
Or see how far your goes?

The record that you are trying to play maybe a 45rpm recording. Some 45's were released in album size recordings.

Hello the turn table has two speeds. 45rpm and 33rpm (rotations per minute) If you are playing a record that takes up the entire turntable you need to set it on 33rpm. For the records that only take up half of the turntable you want to set it on 45rpm. Setting the turntable on the wrong setting for a certain size record can make the record play to fast of to slow.

Mismatch speeds on older turntables is normally due to either 1) a kink in the speed switch mechanism or 2) a hardening and slipping of the rubber drive wheel.
A very small motor with a chamfered shaft drives the rubber drive wheel, and the wheel is moved by the speed control up and down the drive shaft to produce various rpm speeds.
In your case, it's likely turning at 45rpm because it isn't settling onto the 33rpm part of the shaft.
Piddle with the speed control, then count the speed (number of turns in a minute) You'll figure it out!

Could be fuse in plug,drive belt,motor itself

Check that the lever is actually making the contact with the 45 rpm switch position and completing the circuit as it would seem everything else works. The only other thing it could be is a break on the pcb, but that is unlikely.