Music Hall mmf-7 spins faster

My feeling is that pursuing a variac-type device is not worthwhile at this point. Although I'm not familiar with this particular design, I would expect the design of any turntable to be essentially insensitive to ac line voltage variations, within a reasonable range (although it quite likely is sensitive to ac frequency); you've measured that the voltage is perfectly reasonable; you've tried a voltage regulator; you've tried the turntable at another location; and you've tried two alternative ac power supplies (your friend's, and the Speedbox).

Another thought is that in my (extensive) experience as an electrical engineer, often when a problem is particularly baffling, and making all kinds of substitutions does not help, it turns out that there are two problems simultaneously present. Such as one of the substitute parts having a similar problem to the original. I don't know what that might mean here, but it's something to think about while you wait for the next motor to arrive.

Regards,
-- Al

Well, I'll wait until I receive the new motor some time next week.

And, Dweller, I emailed (member) TVAD asking him to participate in the dialogue. Let's wait and see what he will bring to the discussion. Thanks.

Finally, I think member TVAD could advise you better than I (BTW, TVAD is a former MMF-7 owner).
Dweller (Threads | Answers)

I heard speed variations in my MMF-7, and the solution I chose was to sell the table and buy something else. I didn't spend any time trying to fix the MMF-7's speed issue. It wasn't worth my time.

I jus tried my friend's mmf-7.1 in my system and it played beautifully: no speed problems whatsoever. I have offered him to buy it and he agreed (he is going back to Rega).

But, I still need to make the mmf-7 work: I'll give it to my older daughter (now a college student) who has a keen interest in audio (I guess the apple didn't fall far from the tree).

Does your friend's interest in going back to Rega raise a caution flag?