Turntable Runs too fast

 

Jeremy
Unregistered guest
I have a belt-driven Yamaha YP-450 turntable. I know it's no great shakes (i.e. not remotely audiophile), but until recently it was letting me enjoy listening to my records. But for some unknown (unknowable?) reason, it has started to play records too fast at both 33.3 and 45 RPMs. I have searched for answers on the previous threads here and on the broader internet and have come up with nothing.

Does anyone know what could be causing this and how it might be remedied (short of buying a new turntable)?

Thanks in advance,
Jeremy R.
 

Jeremy
Unregistered guest
After doing some rudimentary calculations, I have learned that my turntable is running at 35.6 RPM and 50 RPM when it should be 33.3 and 45. Can anyone help me?
 

Silver Member
Username: John_a

Post Number: 388
Registered: Dec-03
That's 10 per cent. It's a lot. It's just possible the motor is running faster for some reason connected with your power supply. After that, the speed of rotation of the turntable platten is fixed by the ratio of the diameters of the two wheels connected by the belt, and I don't see how that can change suddenly. You could maybe put a spacer, like some thick tape, round the circumference of the larger drive wheel, under the platten, to increase its diameter 10 %, giving a lower gear ratio. But you'd have to be careful and take a look at the possibilities of breaking or derailing the belt. It would be a bit of a hack, but could work, depending on the design.

If the belt is a rubber "O" ring then you probably can't do that, but then the explanation could just be that the rubber has perished, and now fits into a smaller effective diameter on the drive pulley. I find that a bit far-fetched. But examine the belt and the drive wheels to see if they look OK.
 

Silver Member
Username: John_a

Post Number: 389
Registered: Dec-03
...or the belt is riding on a larger effective diameter on the motor pulley. That seems more likely, on reflection. Take the platten off and have a look. Maybe the motor pulley has accumulated some junk, and just needs cleaning. 10% larger would not be impossible, it is usually quite a small pulley wheel.
 

Jeremy
Unregistered guest
Thanks for the response, John A.

I think the belt on my turntable is a rubber "O" ring (it looks like a big black rubber band).

As for the motor pulley, let me be sure that I know what that is - is it the little spinning wheel that effectively drives the turntable? If so, it is quite small - about as large in diameter as the tip of one of my fingers.

The belt looks OK, but it does not snap too tightly into place, which makes me think it may have deteriorated somewhat. If that's the case, than I doubt it was a sudden onset problem. (My wife has been complaining that the turntable was playing the 45s too fast for several months, but I was too obstinate to believe it until recently.)

Getting a new belt is relatively straightforward and cost-effective (about $20 from Elex Alatier), but I am still a little bit reluctant to go for it when I'm not sure it will solve my problem.

I have also read that servo controlled turntables lock the platter speed to some kind of stable reference point that can occasionally become damaged. (I read about this here: http://www.repairfaq.org/REPAIR/F_audiofaq3.html#AUDIOFAQ_011 ) Of course, right now I can't recall if my turntable is servo controlled or not. I'll check back at home this evening.

Does anyone have any experience with this?

Thanks again,
Jeremy R.
 

Silver Member
Username: John_a

Post Number: 410
Registered: Dec-03
Jeremy,

thanks. Yes, it could be the servo mechanism, if there is one, but I think I recall they were more common on direct-drive turntables, and these usually had a stroboscope and adjustable speed, too. There should be some independent way to check if this is the problem, but I can't think of one off-hand. Sorry I don't know your specific model.

By "motor pulley", yes, I meant the small one. It rotates much faster than the platten pulley - the belt connects and gives a large step-down gear ratio, more or less the opposite of the chainwheels on a bicycle.
 

VeryModern
Unregistered guest
Thank you so much, Jeremy, for your post. A couple of weeks ago I'd searched and found just about nothing about this very topic. Now, thanks to your posting and John A's response, I found enough detail to fix this very same problem on my own machine.

Mine is a very non-audiophile BSR model integrated into a Brother stereo w/ an 8-track player and AM/FM tuner.

It was playing fine, and then quite suddenly started playing too fast. I hadn't gone through any calculation to determine by what percentage it was too fast, nor had the idea occurred to me until after I read your post.

Anyway, you inspired me. I reviewed the repairfaq link you found, tried tightening up the motor's mounting underneath the turntable, to no avail. I then saw on that page how to remove the platter (something I'd have been reluctant to do w/o instruction) and cleaned things up and made further adjustments to find success!

My turntable was set up like this:

a fairly freely rotating metal core disk with a rubber outer portion is mounted to some levers that move w/ the speed control and with the start/stop action.

On one side, the edge of the rubber wheel would touch directly the inner plastic edge of the platter that rotates with the record atop of it. Its other side would, when engaged, touch the shaft of the motor. The motor's shaft has the widest circumference towards its base, which is where the wheel was tending when the player was set to 78 RPM. In the narrower middle section, the wheel would be positioned when set to 45 RPM, and at the narrowest top section, that'd be for 33 RPM.

I cleaned the rubber wheel with isopropyl alcohol. Its top/bottom sides weren't much hassle but the side edge that is driven by the motor on one edge and moves along the platform on the other was something of a chore to get clean.

I also cleaned rubber residue off of the motor shaft, which was particularly noticible on the center (45 rpm) section.

I further cleaned the residue from the inner edge of the platter.

This residue could have increased the circumference of the motor shaft where contact was made with the rubber wheel, causing increased rotations per minute.

There was also a screw that controlled the position (vertically) of the mounted rubber wheel. I think it was a little on the low side, meaning that the 33 setting was partially on the uppermost part of the shaft as it should be, ans partially on the middle part of the shaft, which was supposed to be for 45 RPM.

So I was sure to position that screw in an aim to get the rubber wheel touching the center portion of the correct division of the motor shaft - that is, neither towards the top nor towards the bottom of the appropriate section.

The hardest part really was getting the c-clamp back on the spindle once I'd replaced the platter. I did gouge the inner part of the plastic a bit in attempting, but not until I'd heard the satisfaction of a properly sped record playing back an old familliar tune no longer sounding like the Chipmunks!

Thanks once more.... I am proud of me.
 

Silver Member
Username: John_a

Post Number: 607
Registered: Dec-03
Very Modern,

Great. Really good to read.

BSR use to supply record turntables to the world, including Sony, as well as making their own. They made great stuff. Unfortunately, they got taken over by market researchers and accountants.

I once ended up visiting the factory to explain what was wrong with their "State of the art" direct-drive, quartz-lock, strobe equipped ADC turntable. Apart from quality control that was a digrace to any company that did not think it owned its customers, the basic problem was that it was built like a large acoustic microphone.

I have just discovered DVD-Audio. There are some threads under "CD players" and "Receivers".

What I discover is that CD was a retrograde step. Some of us suspected it all along. We have all been taken for a ride for twenty years.

Hold on to your LPs, and your turntable!
 

Jenny Lynn 1220
Unregistered guest
Oh, I definately have to try this, I'm in the same boat guys :-(
 

Unregistered guest
my technics SL-QD2 turntable runs way to fast so fast the needle won't even think about tracking.abody have a clue as whats going on.
thanks
 

kester
Unregistered guest
my harmon kardon was not able to be controlled by the pitch control anymore and found that the motor was okay but the pitch control was not after a good cleaning and not replacing it works awesome now
 

Anonymous
 
@mike chespro, posted on Saturday, September 18, 2004 - 09:52 pm:
my technics SL-QD2 turntable runs way to fast so fast the needle won't even think about tracking.abody have a clue as whats going on.
thanks

I've heard about a SL-1210 running wild. It ran way too fast. One of it's magnet coils was broken and caused this error.

Maybe this helps finding the error.
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