Hello Hunt 23,
Welcome to the forum.
Can you please let me know what country you live in this will help re the advice and if you need to buy parts or need the advice of a professional then we know where to send you.
The Rowe Ami R-74 turntable motor works on 110 volts which is none adjustable.
What can effect speed is a turntable/platter that has oil on the rim (remove and wash down with soapy water, dry off and put one spot of oil an the turntable shaft only), the idler wheel could be worn or could have oil on its surface (remove the idler wheel and the linkage and wash them all, once dry one spot of oil on the each of the pivot points of the linkage and the shaft of the idler wheel).
The motor could be gummed up with old oil, strip down and remove any build up, once clean reassemble and put one drop of oil on the upper bearing pad and if it is fitted with an oil tude to the bottom bearing then another drop of oil.
If you are in Europe operating on 220/240 volts then the turntable motor shaft will be fitted with a speed spring (fitted to convert from the original fequency or 60hz to 50hz for the european system) that may be worn.
If you are in Europe please contact me or if you can not locate the parts worldwide by all means contact me we export to most countries.
Regards
Alan
Alan Hood
ami-man
UK