Turntable too slow!

I picked up a used Rotel RP-2400 a while back, which is a belt drive semi-auto table. Problem is, it seems a tick too slow. It has no strobe and no speed control but I can tell it's slow. The belt looks new, and it's nice and tight but I have no idea if it's even the correct belt. I have a funny feeling that I'd be wasting $20 with a new belt. So I guess the question is, other than the belt, what can cause a slowdown? The platter turns freely and the motor runs smooth, so what else is there to check? Any suggestions?

Don't know if the RP-2400 has an AC or DC motor. Tables with DC motors generally use an electronic control to switch speeds from 33 to 45. And will just about always have a pitch control hidden somewhere. Possibly holes on the bottom for adjustment with a screwdriver. Would need to buy an inexpensive paper strobe disc in this case. Tables with AC motors generally switch speeds with a mechanical control that moves the belt to different sized sections of the drive shaft or requires that you manually move the belt. To my knowledge, AC motors usually run at the correct speed unless they are damaged or the belt is too loose or tight.

I'm not sure if it's AC or DC either. I could not find a hidden control (I thought there would be one too!).

It does have a thing that slides the belt down to a different sized part of the shaft for 45/33. I'm not sure if 45 runs right, I don't have any 45's! I'll have to try to find one to try it.

...some models(unfortunately yours is not archived) have two holes in the bottom pan that give access to speed adjustment screws...given that speed changes are done by physical movement of the belt, that probably does not apply in this case.

DD TTs look to be DC motors and belt-drive can be AC or DC...again yours is not listed, so an educated guess would be synchronous AC...locked to the AC line freq.

The speed is a product of motor shaft and platter diameter, so I don't think a new belt will help...IMO, it would have to be really undersized to provide the tension required to put that much drag on the drive components, but...hey, anything is possible...although I would think the bearings might have some uneven wear if that were the case...you could try to measure the belt vs. the path's distance.

Now for the 64 cent question? How do you know the speed is off? Are you comparing the pitch to another TT? If so, how do you know IT'S not off?

jimHJJ(...don't mind me, just babbling...)

Yeah, I compared it to another table after listening to a few records and thinking to myself it sounded a little slow. I have a DD Pioneer that has a strobe and it sounds great, but it's so obvious to me that the Rotel is slow. I can't listen to it! Once you've listened to enough Yes and Rush, you know what Geddy Lee and Jon Anderson sound like! It's obvious when those guys are slowed down :)

http://www.enjoythemusic.com/freestuff.htm has a few .pdf files of strobe discs you could download and print out. That way you could verify the table is slow and use them to adjust speed if you find a way to adjust that.

James

I would get a new belt anyway. Even if it seems up to snuff it may not be. Cover all the bases.

use a neon or fluorescent light, they go on and off 60 times a second. it stops the strobe for 33 1/3 if its right on. same for the 45 rpm band. you will then know.

if it seems to go in one direction or another, its slow or fast depending on direction. its easy to figure out.

Quote:

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Originally Posted by N. Abstentia

I can't listen to it! Once you've listened to enough Yes and Rush, you know what Geddy Lee and Jon Anderson sound like! It's obvious when those guys are slowed down :)

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Those guys are getting older, so maybe their records automatically adjust to their age/voice?? ;)

JD


ps - Audiokarma.org has a bunch of knowledgeable TT guys, including a few who repair them for a living who will answer posts on a regular basis. Perhaps post your question over there too, although it sounds like someone here has probably nailed it. I bet the Rotel has a speed adjustment hidden somewhere.

You might have a point there!

...that the platter bearing may need to be cleaned and lubed. Oil and grease (mostly grease) can get gummy and so friction goes up. Also, make sure the belt pully is clean of lube where the belt rides on it. If the pully needs to be cleaned, the belt does too...

Laz

start putting electrical tape around the motor pulley. One layer at a time, you will find it won't take much to speed it up a bit. Very common to do the other side on a P3.

I would agree and suggest that the bearing and the pulley be lightly lubed, yet you might want to swab with a q-tip to clean off the gunk buildup, if any. This is what I do when my turntable begins to run slow, but then again its 30 years old ;). Good luck.

As others have suggested, clean and lube the TT main bearing. I like a viscous lube such as gear oil - it it's good enough for Rega, it's good enough for me (at least it smells like hypoid gear oil on my Planar 3...). I drained the factory fill lube out of the bearing, flushed with mineral spirits ("paint thinner") several times and refilled just above the ball thrust bearing with 75W-90 GL-5 hypoid gear oil. If the motor hasn't been lubed for awhile, might not be a bad idea for a drop (NO MORE!) for each exposed shaft bearing after a quick swish with a mineral spirit wetted Q-tip swap at the base of the exposed motor shaft(s) to clear whatever crud may be lurking. That old belt may be the culprit, too. Looks are deceiving as the saying goes. The contact surface may be "ground" to a less than tractive grip from years of starts and stops. Perhaps the combo of a slippery belt and binding bearings may have slowed Geddy Lee and Jon Anderson down more than their years and circumspect lifestyle ever could...