Music Hall mmf-7 spins faster

I suspect you had a lemon...seeing the other table work great.

Toilet paper. Is there any problem it can't solve?

Indeed, Tom.

And, thanks for the tip. Happy Thanksgiving!...

My hunch in explaning the faster speed is that with your momentary loss of composure, you accidently had the belt on the wrong pulley sheave. You might consider something more permanent than a piece of toilet paper to keep the pulley sheave locked onto the pulley shaft. As torque is applied at each start up, that paper binder will likely loosen up and start to slip again. Maybe some kind of glue or cement that's compatible with plastic and adheres to metal.

Glad you finally found the problem. All's well that ends well.

Tom

Actually, it was too fast at first (don't ask me how or why); then, lately, it almost wasn't turning at all: that's what called my attention on the rod and the pulley. I guess I somehow got lost into the measuring and the swapping of parts between the 2 units.

And, yes, I am so glad it's solved! I can now give the mmf-7 to my daughter (her birthday is in about 2 weeks), keep the mmf-7.1 and think about my VPI purchase while I listen to some fine LP's...

Wow! Seems counter-intuitive, though, that a loose fit between the rod and the pulley would result in too fast a speed. Too slow a speed, or an erratic speed, certainly would be understandable. In any event, glad it's solved!

Regards,
-- Al

Finally, some closure: I have both turntables (mmf-7 and mmf-7.1) spinning correctly now. After a lot of tweaking, I finally put a little (toilet) paper on the small rod on top of the motor before easing the pulley, giving it a snug fit. Since then, no more speed problems. It even works perfectly with the Pro-Ject Speed Box II now. In fact, there was no adjustment screw (and no place to insert one) at the base of the motor pulley, thus making it going either too fast (or too slow): "élémentaire, mon cher Watson!" as the French would say...

No, I didn't. Thanks for letting me know. I will have to pass however. The VPI purchase will come some time in the second quarter of 2010 (at the latest), preferably a ScoutMaster. Thanks again...

I am back with the conclusion: there isn't any.

Twad was right: the mmf-7 is a joke. With the new motor, it almost does not spin at all. I don't see any reason to use my time trying to understand what's wrong with this turntable. I'll be using the mmf-7.1 for the shortest time period possible and buy a VPI. Cheers all...

I am currently away from home; I will resume all (measurements, swapping parts, etc.) upon my return next week. Thanks all.

Measure the diameter of the platter on both units. Try and find someone who has a set of calipers. They are used by machinsts to make precision measurments.

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96509

I have a MMF-7 with the speedbox and am V happy with it, till I can get a VPI and then a Teres. ;)

I swapped the motor and, surprise, surprise: it is now much slower, almost not turning at all. I am going to change the platter and the sub-platter now.

Did I say weird?

I am going to swap the motor, the belt, the sub-platter and the platter and see what happens.

I like my MMF-7 -no problems whatsoever.

Lrmellon: Now you can swap all the parts from the new MMF-7.1 and see what happens.

I think the ".1" is a change to the tonearm.
The rest should be the same.

Good luck!

Nope, not at all; he was very happy with his mmf-7.1: just the upgrade bug. I simply asked at the perfect time.

You seem not really happy with Music Hall turntables: may I know why?

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).

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.

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

My only exposure to an audiophile grade variac was at Superior Audio (Chicago) in the mid 1990s. The propriator had a unit made by Merril Audio or Conrad-Johnson? -I can't remember. He used it to warm up his Tube amps (slowly and gently).

You could cruise Ebay or even AGon for used units.

I'm wondering if PS Audio's famous A/C conditioners have a voltage dial-in feature?

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

Dweller, I did some research on the web about variable voltage modifiers (variac) and found them to be a very interesting item and not pricey at all (I confess that I didn't know anything about them before). Would you care to recommend a particular one (preferably sold at The Home Depot/Lowe's or Sears or Radio Shack) that I could use in that kind of application to make sure that I have the correct constant voltage? In addition, would it be "crazy" to use it in combination with my voltage regulator?

Please advise.

As a matter of fact, I did: no change.

The small pulley is clean, the larger one too (as I have tried to correct that speed problem with a Pro-Ject Speed Box II).

I am expecting another motor from Music Hall, but at this rate, I doubt that will change a thing. We'll see...

Just grasping at straws here, but have you at any point taken your complete turntable to another location, such as your friend's house, and tried it there? Although it would seem unlikely, perhaps there is something grossly wrong with your ac power, either the frequency being too high, or unusually large amounts of harmonic distortion. If, as I suspect, the turntable's rotational speed is synchronized to the power line frequency, perhaps that could be the explanation.

Also, you've undoubtedly checked this, but just to be sure, could there be an accumulation of some sort of detritus around the rim of the small pulley, that would in effect increase its diameter?

Regards,
-- Al

Thanks, Al.

I have that reading when the power adapter is connected, but with the motor not running. I have the same with the mmf-7.1.

I don't get what's wrong; there must be a rational explanation (and a solution), I'm sure.

Lrmellon -- Are you reading the 18 volts while the motor is connected and running (in which case it is probably much too high), or when the motor is not connected to the power adapter or is not running (in which case it might be ok, and the best way to tell is to compare the measurement with your friend's table, under the same conditions)?

Re your second question, I have no knowledge of what might be inside the motor assembly, but my guess would be "no."

Regards,
-- Al

One more additional bit of information. The multi-meter reads 18 volts at the motor's power adapter output.

Question: is there any kind of belt inside the motor that might be causing the problem (because it's dilated or something)?. It's definitely not the AC voltage.

Still desperate.

I just finished my testing with a multi-meter (I couldn't locate a variac) and found between 115.6 and 116.7 volts. Better yet, I used a 500W AC automatic voltage regulator (and plugged the motor in): no change. It still spins too fast, somewhere closer to 45 rpm than 33 1/3. I really don't know what else to do. And please note that I used 2 different Music Hall motors with exactly the same results and that the Speed Box II didn't/doesn't change a thing.

I am desperate now.

I'll try but, to be honest, I am fed up with this turntable. Thanks.

Find someone with a multi-meter and check your voltage.
Better yet, locate a variac (voltage modifier), dial in 115 volts and see what happens.
Best of luck...

After oiling the main bearing and the spindle, no change whatsoever. I give up.

I am going to buy a new turntable from another brand. I don't have the slightest clue why this is going on.

Thanks all.

Thanks again, Stefanl. Now, I get it for sure (what I thought I understood is certain now). I will oil both the spindle and the main bearing with Mobil 1 (with teflon). I'll let you know what my results are.

The main 'bearing' is located at the centre of the platter.The spindle pokes up from it and you place the part of a record with the hole in it,through it,to hold the record in place.You take the belt and platter off and take the thing that pokes up out of it's hole.You now have a hole that is empty in the middle of the turntable,that you put oil into.Coat the long metal piece(spindle)that moves in the hole (bearing)with oil as is reasonable for moving parts and place some oil in the hole (bearing) also.The tape trick may not be needed if you oil properly,but the tweak works and that is what is needed.

Thanks, Stefanl: I did read it in the manual. However, I am not sure what "main bearing" means. Where is it located: under (pardon my ignorance)? Please elaborate on the coating of the spindle.

As for warming up the system, it has been back out on top of my rack for more than 6 months now and I have played at leat 7 or 8 LP's so far, even with the atrocious (to my ears) speed problem, both with volume and mute.

I would appreciate any additional comments/advice (but I have yet to put electrical tape around the platter: it seems such a not so elegant trick).

The recommendation for adding bearing oil is in the 7 manual also.Mobil 1 is the suggestion.Rega recommend 80/90 gear oil choice of oils could be important and if your turntable was in the attic for a couple of years,this is the first thing I would try.Make sure you coat the spindle and there is a coating of oil on the walls of the bearing recess and at the bottom of the well.Also play at least 1 album before you test and make adjustments.Warming the system up is crucial as well.

I did try that already, Almarg; thank you. It does spin closer than what it should, but still not at the correct speed. Without the Speed Box II, it's definitely too fast.

I also tried the other AC adapter: same result.

I unfortunately do not have a multimeter to measure those parameters.

Thanks again.

It is indeed in the right groove, Eddaytona: the smaller one (and the larger one, as indicated, when I am using the Speed Box II).

Where is "as indicated" indicated?

The Speed Box appears to output 16 volts ac (VAC), while the MMF-7 appears to come with a 12 VAC wallwart power supply. I note that the ratio of 16 to 12 just happens to be approximately the same ratio as 45 rpm to 33.3 rpm. However the recommendation to use the larger pulley diameter with the Speed Box, for 33.3 rpm, would seem to make sense only if the motor speed were inversely proportional to supply voltage, which seems nonsensical. .

I don't know what kind of motor the MMF-7 has -- whether it is synchronous to the power line frequency, and what the sensitivity of its speed to line voltage is. But very conceivably it is different from the motors used in the Pro-Ject turntables for which the Speed Box is intended.

I would therefore do three things:

1)Try using the Speed Box while the belt is placed on the smaller rim of the pulley.

2)Try the 12 volt ac power supply from your friend's turntable.

3)Use a multimeter, set to measure ac volts, to measure the voltage provided by the power supply that came with your turntable, and compare it to what your friend's power supply puts out. Since you will probably have to disconnect the power supply from the motor to make that measurement, keep in mind that the voltage figures to be higher than it would be with the motor connected and running. Which is why I suggest comparing the readings of the two power supplies.

Re bearing oil, see page 14 of the manual for the 7.1, which I assume is similar to the 7 in that regard.

Regards,
-- Al

Thanks for your input, guys. But, Stefanl, lubricant to the bearing? Where exactly? Please elaborate.

Mofimadness: there's really no need for a strobe disc. My ears (and a couple of others) have indeed verified the (much) increased speed.

Dweller: I am pretty certain it's not high voltage. I live in Commack, New York (115V) and the added Pro-Ject Speed Box II -- suggested by Roy Hall himself and a couple of audiophile friends as well -- should have corrected any (major and/or minor) speed 'discrepancy'. In addition, I am using a Music Hall belt (the original one and a new one, bought directly from Music Hall). My line preamp is an Audio Research SP16L and my phono preamp an EAR 834P (with Cardas Golden Cross 1.0-meter interconnects). It does happen to all LP's, ever since I went back to analog about 6 months ago (the mmf-7 was stored in the attic for about 2 years). Lastly, the motor is "in the hole" of the plinth, as indicated.

I really don't know what else to do, except maybe buy a new turnatable, preferably from another manufacturer (maybe Rega or VPI). Roy Hall just sent me a new motor: I'll try it as soon as I receive it and report back to this thread.

Misc. thoughts:
-Could this be caused by unusually high voltage?
BTW, in which country do you reside?
Are you using a 115 volt model on a 220 volt system?
-Are you using a Music Hall belt or something else?
-Are you using an analog preamp or is the signal being converted into digital first (with some kind of pitch adjustment after)?
-Is this effect happening to ALL of your albums?
-How long has this been happening (is this a new TT)?
-Is your motor "in the hole" of the plinth or is it outside somehow (stretching the belt)?

P.S. I'm a MMF-7 owner also.

Have you put a strobe disc on it to "visually" verify that is running fast?

You could also be running on a 'fast' bearing,meaning you need to add some oil to the bearing well.This occurs when a turntable bearing spindle has run out of lubricant and runs too fast,metal on metal.A few drops of oil or whatever is the recommendation by the manufacturer will cure a too fast problem also.Good luck!

It is indeed in the right groove, Eddaytona: the smaller one (and the larger one, as indicated, when I am using the Speed Box II).

And, Stefanl, thanks: I will try your trick. However, I am still not sure why it would spin faster: on the Billie Holiday LP "Songs For Distingué Lovers" (that I know very well), although the instruments may appear to be playing at the correct speed/pitch, Ms. Holiday's voice is almost unrecognizable, as if all the "low-toned hurt" in her voice was nowhere to be found. On Pat Metheny Group's LP "Offramp", it's like Metheny's guitar (or Lyle Mays' piano) is playing a third faster than what was recorded. And I am very familiar with these recordings, be it on tape, LP or CD. Very frustrating indeed!...

Are you sure the belt is in the right groove on the motor? One is for 33 1/3, the other is for 45rpm.

Yes,you can widen your platter by applying maybe 1 or 2(?) winds of electrical tape around the platter's edge.I do this with a Rega's sub-platter and it slows it down to run at correct speed.You can experiment with this until you find the exact number of windings you need.Apply single layers evenly and trim with scissors.Test with a strobe and needle in the groove playing a record.