View Full Version : Pioneer PL 50 runs too fast


keithpgdrb
03-13-2012, 12:16 AM
Hey all,

My PL-50 runs too fast. I have corrected all of the obvious culprits.

1. oiled it with good sewing machine oil
2. got the proper belt from vintage electronics (.net)
3. cleaned up both the capstan and the platter to make sure there is no left over goo from the old belt. its looks great actually.
4. verified that I have the correct capstan installed for the USA

All of the above have done nothing for the speed. The only solution that I have come across outside of grinding down the capstan (which I'm not doing) was a passing mention of increasing the platter width with electrical tape. This was mentioned as working great, but no one really followed up with any other comments. I understand that there are speed issues with this table, and I believe the pl 41 as well. Its never been sure why though.

SO, I come to you all once again to figure out a Final solution to this issue. if you have had this problem, what did you do to fix it? anyone else try the tape? is there another solution I should be looking into? would this have anything to do with house current? I wouldnt think so, but who knows. lets figure this out. :yes:

Bucky Badger
03-13-2012, 12:28 AM
#4 is what I would have suggested. Did you try the other one?
If you did and it didn't work I hope that someone has an answer for ya.

keithpgdrb
03-13-2012, 12:31 AM
Thanks Bucky. I know there is an answer. I just know it. I've read all kinds of posts of this problem. but very few solutions.

Bucky Badger
03-13-2012, 12:43 AM
Great turntable btw. I sold mine but know that I will have one again. I am always lookin'.

keithpgdrb
03-13-2012, 12:55 AM
Yeah, I like it a lot, and its in good shape. Nice simple table. But I'm a musician, and this speed issue is driving me crazy. I have faith though. I will prevail.

Junknewbian
03-13-2012, 01:20 AM
In my opinion, I can't imagine loving a table with a chronic speed problem. I would get another turntable, for less (aggravation, money) than you might spend to try to perfect this one.

keithpgdrb
03-13-2012, 01:27 AM
In my opinion, I can't imagine loving a table with a chronic speed problem. I would get another turntable, for less (aggravation, money) than you might spend to try to perfect this one.


Part of me agrees with you. But when you find a vintage table in good shape, the effort can be worth it. The table sounds good but for the speed issue.

Bucky Badger
03-13-2012, 01:37 AM
It really is a nice table Junknewbian. Heavy and well made. And, it might not be a very big problem to fix.
I like your attitude keithpgdrb. Keep it up.
To clarify, did you try both capstans?

keithpgdrb
03-13-2012, 01:57 AM
It really is a nice table Junknewbian. Heavy and well made. And, it might not be a very big problem to fix.
I like your attitude keithpgdrb. Keep it up.
To clarify, did you try both capstans?

nope, I only have the one capstan. the one with the beveled bottom. supposed to be the right one. Never had a second one.

gridleakrick
03-13-2012, 02:10 AM
Change the belt. I've worked on a lot of turntable and, in my experience, 9 times out of 10 changing the belt will correct the speed problem. Small variations in belt diameter, width or thickness can cause the speed to be off. It helps to have a stock of belts available to try to find the one which works right. I have to do this on a regular basis. How wide is your replacement belt? Most Pioneer turntables want narrow belts (around 0.185") but many vendors sell ones of 0.2"-0.25" width and claim they are the right ones.
Rick

Bucky Badger
03-13-2012, 02:13 AM
:scratch2:
I just looked at the manual and it does say that the 60hz capstan has the groove cut in the bottom so you should be right on. Do you have the manual?
One is available on VE for free.
Also, do your speed selector buttons work?

keithpgdrb
03-13-2012, 08:40 AM
Change the belt. I've worked on a lot of turntable and, in my experience, 9 times out of 10 changing the belt will correct the speed problem. Small variations in belt diameter, width or thickness can cause the speed to be off. It helps to have a stock of belts available to try to find the one which works right. I have to do this on a regular basis. How wide is your replacement belt? Most Pioneer turntables want narrow belts (around 0.185") but many vendors sell ones of 0.2"-0.25" width and claim they are the right ones.
Rick

I changed the belt twice. Speed remains the same amount off. I don't think it's the belt. How much speed variation would you get with the wrong belt? I have to find a way to measure how far off the speed is. It's obvious to me.

keithpgdrb
03-13-2012, 08:42 AM
:scratch2:
I just looked at the manual and it does say that the 60hz capstan has the groove cut in the bottom so you should be right on. Do you have the manual?
One is available on VE for free.
Also, do your speed selector buttons work?


Yes. I have all the manuals and the speed selector buttons work fine.

boreas
03-13-2012, 09:38 AM
I have to find a way to measure how far off the speed is. It's obvious to me.

VinylEngine has downloadable strobe discs. You'll want one for 60Hz. After downloading, print, cut out and put on the platter under a strong artificial (preferably fluorescent) light.

I printed mine on heavy photo paper, laminated it to a piece of a manilla file folder and then coated it with spray lacquer. Been using it for years.

John

keithpgdrb
03-13-2012, 09:42 AM
VinylEngine has downloadable strobe discs. You'll want one for 60Hz. After downloading, print, cut out and put on the platter under a strong artificial (preferably fluorescent) light.

I printed mine on heavy photo paper, laminated it to a piece of a manilla file folder and then coated it with spray lacquer. Been using it for years.

John

I have strobe lines on my test records. All they do is confirm that I'm running fast. Not how much.

boreas
03-13-2012, 10:28 AM
I have strobe lines on my test records. All they do is confirm that I'm running fast. Not how much.

Oh, okay. I don't think you mentioned anything other than your ears alerting you. So, how quickly are the hash marks moving, IOW how much time between one hash mark aligning with a fixed point and the next? You can use the arm as your reference.

And you'd be surprised at how much you can do with different belts, different lengths, widths and thicknesses. You mentioned VintageElectronics. You might try your next one from Turntable Basics (http://www.turntablebasics.com/belts/pioneer.html).

John

epifanatic
03-13-2012, 10:31 AM
Does this table have pitch control pots? If so, they probably need a good shot of Deoxit.

GreatTone
03-13-2012, 10:34 AM
My Ariston RD11S is a hair fast. By a hair, I mean it gains about one second per minute. Comparing the same song to a CD, I can definitely hear the vinyl being sharp, but it's extremely small. I'm a musician also, and I can't notice it unless I'm comparing the vinyl to something else. I guess I'm lucky I don't have perfect pitch, though I do have excellent relative pitch.

I just put it down to PRAT and consider it a feature, not a bug.

boreas
03-13-2012, 10:40 AM
Does this table have pitch control pots? If so, they probably need a good shot of Deoxit.

No, the PL-50 and PL-50A motors are AC synchronous. Motor speed is controlled by mains voltage and frequency only.

KentTeffeteller
03-13-2012, 10:52 AM
Check and make sure your AC motor's rubber bushings are in good condition. Also, make sure your motor pulley is at correct height.

Dr Tinear
03-13-2012, 10:54 AM
Does the motor have a run capacitor? If so, check to see if it's gone open or drifted off value with age and replace it if it's bad.

GreatTone
03-13-2012, 11:00 AM
Does the motor have a run capacitor? If so, check to see if it's gone open or drifted off value with age and replace it if it's bad.

I've wondered about that with my Ariston, which has an original cap. Does the cap value affect the speed?

keithpgdrb
03-13-2012, 11:03 AM
Oh, okay. I don't think you mentioned anything other than your ears alerting you. So, how quickly are the hash marks moving, IOW how much time between one hash mark aligning with a fixed point and the next? You can use the arm as your reference.

And you'd be surprised at how much you can do with different belts, different lengths, widths and thicknesses. You mentioned VintageElectronics. You might try your next one from Turntable Basics (http://www.turntablebasics.com/belts/pioneer.html).

John

I believe I got the last one from turntablebasics. vintage electronics has a pretty solid rep for having quality belts. I honestly dont think its the belt. both belts I have run about equally fast.

keithpgdrb
03-13-2012, 11:05 AM
My Ariston RD11S is a hair fast. By a hair, I mean it gains about one second per minute. Comparing the same song to a CD, I can definitely hear the vinyl being sharp, but it's extremely small. I'm a musician also, and I can't notice it unless I'm comparing the vinyl to something else. I guess I'm lucky I don't have perfect pitch, though I do have excellent relative pitch.

I just put it down to PRAT and consider it a feature, not a bug.

I dont have perfect pitch or anything, but albums are audibly fast. donald fagan's voice is high, but its just a bit too far off. I'll have to try the hash mark measuring to see how much its off.

keithpgdrb
03-13-2012, 11:07 AM
Check and make sure your AC motor's rubber bushings are in good condition. Also, make sure your motor pulley is at correct height.

I have not looked into the bushings. I'm not sure where id find them. I'll check the service manual for that.

The belt rides right in the center of each portion of the capstan if thats what your referring to.

keithpgdrb
03-13-2012, 11:09 AM
Does the motor have a run capacitor? If so, check to see if it's gone open or drifted off value with age and replace it if it's bad.

I dont know. I'll have to look for that as well.

GreatTone
03-13-2012, 11:32 AM
I have not looked into the bushings. I'm not sure where id find them. I'll check the service manual for that.

The belt rides right in the center of each portion of the capstan if thats what your referring to.

I believe the bushings he's referring to are the rubber things that attach the motor to the plinth. The fact that your belt rides in the center of the pulley tells me it's set up right.

How much higher is the music? Half a step, or more? That would be tough.

You may want to time a song on a CD, then time the same song on vinyl, and compare. That's how I figured out mine was running a second per minute fast. Might help to know just how fast it's going.

boreas
03-13-2012, 11:49 AM
You may want to time a song on a CD, then time the same song on vinyl, and compare. That's how I figured out mine was running a second per minute fast.

You'd be surprised at how many recordings were done off-speed. Checking against a CD of the same cut only works if the CD was made from the same master and wasn't speed corrected somewhere along the way.

John

keithpgdrb
03-13-2012, 11:55 AM
I believe the bushings he's referring to are the rubber things that attach the motor to the plinth. The fact that your belt rides in the center of the pulley tells me it's set up right.

How much higher is the music? Half a step, or more? That would be tough.

You may want to time a song on a CD, then time the same song on vinyl, and compare. That's how I figured out mine was running a second per minute fast. Might help to know just how fast it's going.

well, I timed a song. 2:32 on the table, listed as 2:38 on the LP. on cd, its about 2:37.5

boreas
03-13-2012, 11:58 AM
well, I timed a song. 2:32 on the table, listed as 2:38 on the LP. on cd, its about 2:37.5

4%

John

KentTeffeteller
03-13-2012, 12:06 PM
Yes, the rubber pieces which attach the motor to the plinth. If those sag, the motor gets out of alignment just enough to throw off the speed. Common issue with age on many older belt drive Japanese turntables.

keithpgdrb
03-13-2012, 12:07 PM
yep, about 4%. too much for me. also, the difference in speed is throwing off the resonance point of the cart. puts it right in the area you dont want.

So, established that its fast. I dont see any info on a capacitor for speed. what next?

keithpgdrb
03-13-2012, 12:14 PM
Yes, the rubber pieces which attach the motor to the plinth. If those sag, the motor gets out of alignment just enough to throw off the speed. Common issue with age on many older belt drive Japanese turntables.

took a look at this, but I dont see any sagging, and the belt is riding correctly. It makes sense that if the motor sags, the belt would then ride on a different part of the capstan, thus messing with the speed. is this what your talking about, or am I missing something in my understanding? if not, I dont think thats the problem.

boreas
03-13-2012, 12:20 PM
So, established that its fast. I dont see any info on a capacitor for speed. what next?

It's definitely a bit of a bodge but electrician's tape on the platter does work.

Meanwhile, can you see any differences between the two belts you have?

John

keithpgdrb
03-13-2012, 12:30 PM
took a look at this, but I dont see any sagging, and the belt is riding correctly. It makes sense that if the motor sags, the belt would then ride on a different part of the capstan, thus messing with the speed. is this what your talking about, or am I missing something in my understanding? if not, I dont think thats the problem.

so, to understand this whole sagging motor thing, I looked at the capstan area. I see now that the motor is suspended by springs and rubber. I pushed the whole thing in just the slightest bit from one of the springs, thus shortening the distance between the capstan and the platter, also making the belt looser. didnt do anything. released it back to its original position, same. I was hoping this would have been the case, but I just dont know.

I agree that the tape isnt a real fix, but if no other solutions present themselves, I may think about it more seriously.

boreas
03-13-2012, 12:36 PM
Within limits, the belt will "hunt" for the fat spot on the capstan, simply riding higher or lower on the platter to do so. I've definitely found that different spec belts, all riding on the correct spot on the capstan will produce different speeds. Differences in width seem to make more of a difference than do differences in length. :dunno:

John

keithpgdrb
03-13-2012, 12:42 PM
It's definitely a bit of a bodge but electrician's tape on the platter does work.

Meanwhile, can you see any differences between the two belts you have?

John

the original replacement belt is a bit thinner, and a little wider then the newer one. I did the song speed test, and it seemed basically the same, accounting for human error.

keithpgdrb
03-13-2012, 12:45 PM
Within limits, the belt will "hunt" for the fat spot on the capstan, simply riding higher or lower on the platter to do so. I've definitely found that different spec belts, all riding on the correct spot on the capstan will produce different speeds. Differences in width seem to make more of a difference than do differences in length. :dunno:

John

how much of a speed variation have you found in your experience. could a different belt compensate for a 4% problem? Both of these belts were listed for the pl-50. interesting to me that they look different. I will say that the newer belt definitely feels of higher quality. but I digress. what do you think about the belt variation?

boreas
03-13-2012, 01:23 PM
how much of a speed variation have you found in your experience. could a different belt compensate for a 4% problem?

Yes, I think so.

Both of these belts were listed for the pl-50. interesting to me that they look different.

Vintage electronics lists an FRX-35.1 as I recall and Turntable Basics is an FBM-35.1. These would be the same length but of different widths, maybe different thicknesses too. That difference was why I suggested Turntable Basics but you were ahead of me there.

I will say that the newer belt definitely feels of higher quality. but I digress. what do you think about the belt variation?

I haven't "refined my theory" on this. I just had the experience of trying to bring the speed in on a Yamaha YP-B2 I picked up by trying a series of odds and ends belts I've accumulated. I tried a variety of lengths from 23.6 to 25.0 and found very little difference, all slow to about the same degree. Then I tried a belt that was the same length as one of the other belts I tried but considerably wider and the speed came right up to where it should be. That's why I suggested the one from TTB since it's, nominally at least, narrower and I thought, just as wider made for faster in my case, narrower would make for slower in yours.

John

keithpgdrb
03-13-2012, 04:12 PM
The narrower belt was from vintage. And it is indeed thIcker as well. The other belt is thinner and wider. Both seem to give me the same speed. At least there isn't much difference. I wish i had a bucket of belts to try. I can return the belt, but I wouldn't know what to exchange it for.

GreatTone
03-14-2012, 10:27 AM
Wouldn't tape on the platter make it go faster? The bigger pulley is for 45 rpm, thus faster. I can't remember how bike gears work. I'm confused.

I guess mine is running about 1.5% fast, at a second per minute. 3 seconds per minute would be much more noticeable.

keithpgdrb
03-14-2012, 11:07 AM
Wouldn't tape on the platter make it go faster? The bigger pulley is for 45 rpm, thus faster. I can't remember how bike gears work. I'm confused.

I guess mine is running about 1.5% fast, at a second per minute. 3 seconds per minute would be much more noticeable.

The bike gear analogy is a good one. remember when you would accidentally shift gears and end up peddling really fast, but not going anywhere?? thats what we want here. small capstan, large platter. Reverse that if you need more speed. If I go that route. It still doesnt make a lot of sense to me why its running too fast. I've ordered two correct belts, each different, same issue.

markallen
03-14-2012, 11:19 AM
I'm watching this thread with interest, as my PL-41 runs fast, but as of yet the only reasonable recommendation I've seen is to add a layer of electrical tape to the platter.

Does the motor have a run capacitor? If so, check to see if it's gone open or drifted off value with age and replace it if it's bad.

I'd like the answer to this also. Anyone ever change this out - and get positive results?

boreas
03-14-2012, 11:34 AM
Wouldn't tape on the platter make it go faster? The bigger pulley is for 45 rpm, thus faster. I can't remember how bike gears work. I'm confused.

Bigger drive element (capstan) = faster. Bigger driven element (platter) = slower.

John

keithpgdrb
03-14-2012, 11:41 AM
I'm watching this thread with interest, as my PL-41 runs fast, but as of yet the only reasonable recommendation I've seen is to add a layer of electrical tape to the platter.

I'd like the answer to this also. Anyone ever change this out - and get positive results?

This is why I started this thread. I will not yield until an answer is found. Or I give up and use the tape. lol..

Does anyone with electrical knowledge know where one might start looking for a cap that may have gone bad? All I really see is a motor, but I could be looking in the wrong place.

qpagoda
03-14-2012, 12:17 PM
My PL-50 consistently runs fast, too. Never have found a solution. It is audible.

I measured the speed by putting a piece of masking tape on the rubber mat (as a marker) and counting revolutions for 3 minutes. Three minutes so I didn't have to estimate a third of a revolution. It runs at a consistent 34 rpm.

The service manual shows a 0.1 mF 1,000 V capacitor in the turntable but provides no schematic and doesn't really explain what the capacitor is for or even what type of capacitor it is.

keithpgdrb
03-14-2012, 03:04 PM
My PL-50 consistently runs fast, too. Never have found a solution. It is audible.

I measured the speed by putting a piece of masking tape on the rubber mat (as a marker) and counting revolutions for 3 minutes. Three minutes so I didn't have to estimate a third of a revolution. It runs at a consistent 34 rpm.

The service manual shows a 0.1 mF 1,000 V capacitor in the turntable but provides no schematic and doesn't really explain what the capacitor is for or even what type of capacitor it is.

Hmm. The plot thickens. I'll Try to find out where that cap is. It seems the next logical step when all of our other attempts are going no where. And the issue seems pretty common. It would be great to find a final solution to this issue. For all the pioneer 41s and 50s.

GreatTone
03-14-2012, 03:16 PM
My PL-50 consistently runs fast, too. Never have found a solution. It is audible.

I measured the speed by putting a piece of masking tape on the rubber mat (as a marker) and counting revolutions for 3 minutes. Three minutes so I didn't have to estimate a third of a revolution. It runs at a consistent 34 rpm.

The service manual shows a 0.1 mF 1,000 V capacitor in the turntable but provides no schematic and doesn't really explain what the capacitor is for or even what type of capacitor it is.

That sounds like the right value for a motor run cap. My Ariston only has 2 caps -- a spark suppressor across the power switch, and the motor run cap. Next time I work on it, I'll probably just replace them, as they are like 50 cents each.

keithpgdrb
03-14-2012, 05:17 PM
In the exploded view of how everything fits together, it looks like the cap may be situated right behind the terminal strip lug, whatever that is! lol!!

Maybe I'll open her up tonight and see what there is to see. if there's only one cap, might as well change it. wont hurt, and it could be the fix we're looking for.. The alternative is electrical tape, which I'm trying to avoid.

I just hope the cap isnt buried in the works. Thats a pain. lol.

keithpgdrb
03-14-2012, 06:31 PM
Ok, took a look, and the cap couldnt be easier to get to. Now I just have to figure out what to replace it with. Suggestions?

http://www.audiokarma.org/forums/attachment.php?attachmentid=336149&stc=1&d=1331767816

http://www.audiokarma.org/forums/attachment.php?attachmentid=336150&stc=1&d=1331767816

qpagoda
03-14-2012, 11:13 PM
It's obvious right off that the voltage value of the cap is different from the value in the service manual. Shouldn't be a big deal. 1000 V is pretty high.

It's hard to tell what kind of cap it is. Is it an electrolytic? If it is not electrolytic, I'll be surprised if that cap is the source of the problem.

GreatTone
03-15-2012, 12:08 PM
It's a 0.1uF film cap. Polyester or polypropylene is fine. They are non-polar, so it doesn't matter what way you install it. I assume it's on the AC line voltage, so anything above 250V will be good. Might want to use a 500V or 630V or whatever to be safe.

I doubt it will affect the speed though. I've done some research into caps and AC motors, and the cap seems to be for providing an off-phase pulse of voltage to start the motor and then keep it turning. Without it, the motor just sits there vibrating. While it is important to get the correct value, it has more to do with the platter starting and the motor running without vibration. This is just based on reading though...I was hoping it was a fix for speed issues too, and I don't think that's it.

keithpgdrb
03-15-2012, 12:37 PM
well hell. what to do then. It doesnt make sense. everything on the table is back to stock. correct belt size, with two different belt shapes, lubed, etc. I'm sure it wasnt designed to run fast, so what is the missing piece here?

What are your thoughts with the cap value being different then the service manual? The cap is the only thing I can think of changing.

GreatTone
03-15-2012, 02:21 PM
well hell. what to do then. It doesnt make sense. everything on the table is back to stock. correct belt size, with two different belt shapes, lubed, etc. I'm sure it wasnt designed to run fast, so what is the missing piece here?

What are your thoughts with the cap value being different then the service manual? The cap is the only thing I can think of changing.

What does the manual say the value should be? Changing the voltage value won't change how it works, and 0.1uF is a pretty standard value for turntable motor run caps. If the specified capacitance is significantly different it should be changed anyway to get back to spec so the motor runs smoothly. Caps are pretty cheap too...that one would be about a buck.

petehall347
03-15-2012, 02:51 PM
would be interesting to know if your line frequency is correct in your area .
i was going to say voltage is possibly wrong but that should be between 110 and and 130 ....
you could try cleaning the voltage selector switch it shouldn't do any harm . as long as its set correctly afterwards .i doubt it would be that anyway .

bryanvdz
03-15-2012, 04:01 PM
While I could imagine a synchronous motor running slow, e.g. worn bearings or lack of lubricant, I can't come up with a theory to make one run faster than mains frequency dictates. Your motor is locked in at 1800rpm by design (Actually, if it's a 4-pole motor, it's locked in at 120*Freq/4). If you are running 4% fast, that would require mains freq. of 62.4 Hz, and while there are occasional deviations from the 60Hz standard that cause the utility to regulate, I don't believe any U.S utility would tolerate 62Hz as being 'normal'.

Neither can the capacitor make your motor run fast. And the 450V rating just says its sufficient to handle your 120V mains. I think your motor is fine, and the problem is in the drive mechanicals.

The early low-end Pioneer TTs (I have one, a PL-112D) did have a reputation for running a bit fast, whether by design flaw, or maybe even by design (for some unknown reason), now I'm repeating myself, but I think it's in the capstan/platter geometry.

Having said all that, 4%? That brings A440 to almost 458Hz fercryingoutloud. That's closer to A#. I feel your pain! And I can imagine Pioneer being loose, but that's just sloppy. It really is a puzzle.

It would be helpful to 1) Verify your mains frequency (you need a frequency counter anyway, right?) 2) Determine your motor speed (just a $300 strobe on the capstan, watch the attaching set screw, should sync at 30Hz for 1800rpm). Of course, the trick is to figure it out without throwing money around.

Or you could just build up the platter. But if you're like me, you want to know if your actually fixing it, or masking the problem with a band-aid.

GreatTone
03-16-2012, 09:30 AM
I'm all for diy solutions, but I also have a problem with tape on the platter. It's not exactly a tightly toleranced product. The inner platter on my Ariston is amazingly machined for precision. Seems like the inherent differences in tape thickness, not to mention bubbles and crinkles, would do all kinds of things to the speed consistency, creating more problems than it solves. Or maybe the platter/belt interface is more forgiving than I'm imagining.

I would like to get my Ariston running right at 33 1/3. The music doesn't sound too fast when I'm listening to it, but when I hear the same thing on CD later it sounds a little draggy. But I'd rather have it a few cents sharp and rock solid in (relative) tune, than have it 'A 440' with audible wow.

Maybe someone who has done the tape thing could chime in.

GreatTone
03-16-2012, 03:57 PM
A followup post -- after installing a bathroom vent last year, I have a roll of high quality aluminum tape left over. Wouldn't that be better than electrical tape? Ie, the platter is aluminum, therefore at least the belt's contact surface is the same material. Also, the aluminum tape would potentially flatten better, being metal and all. Thoughts?

I may try it this weekend. Any idea how thick a layer it requires?

boreas
03-16-2012, 04:52 PM
A followup post -- after installing a bathroom vent last year, I have a roll of high quality aluminum tape left over. Wouldn't that be better than electrical tape? Ie, the platter is aluminum, therefore at least the belt's contact surface is the same material. Also, the aluminum tape would potentially flatten better, being metal and all. Thoughts?

I may try it this weekend. Any idea how thick a layer it requires?

Aluminum furnace tape is shiny so it might cause the belt to slip. Also, it's thicker than something like electrical tape so it would be more difficult to "fine tune the speed by adding or subtracting tape.

If I were going to try this I'd definitely use electrical tape. I'd put on a lot at first in the hope of making the platter spin too slow and then remove tape a little at a time until the speed came in.

John

GreatTone
03-16-2012, 06:08 PM
Aluminum furnace tape is shiny so it might cause the belt to slip. Also, it's thicker than something like electrical tape so it would be more difficult to "fine tune the speed by adding or subtracting tape.

If I were going to try this I'd definitely use electrical tape. I'd put on a lot at first in the hope of making the platter spin too slow and then remove tape a little at a time until the speed came in.

John

The aluminum tape I have is very thin -- 0.0025", as opposed to 0.0065" for the electrical tape. The electrical tape is also very shiny and smooth, but maybe less so than the aluminum. However the subplatter on my tt is pretty smooth and polished as well. I haven't tried either though, so I don't know.

boreas
03-16-2012, 06:25 PM
The aluminum tape I have is very thin -- 0.0025", as opposed to 0.0065" for the electrical tape. The electrical tape is also very shiny and smooth, but maybe less so than the aluminum. However the subplatter on my tt is pretty smooth and polished as well. I haven't tried either though, so I don't know.

I didn't realize the stuff you were working with was that thin. If it's not too slippery it should work well. It'll also look a lot better than black electrical tape.

John

keithpgdrb
03-18-2012, 12:05 PM
A followup post -- after installing a bathroom vent last year, I have a roll of high quality aluminum tape left over. Wouldn't that be better than electrical tape? Ie, the platter is aluminum, therefore at least the belt's contact surface is the same material. Also, the aluminum tape would potentially flatten better, being metal and all. Thoughts?

I may try it this weekend. Any idea how thick a layer it requires?

been out of the loop for a little bit here. I think that the aluminum tape sounds fine. If there is any slipping, it would be on startup and wind down. There shouldnt be much actual pulling after it gets started.

I also think the aluminum tape may be the way to go, because of consistent thickness. it shouldnt stretch like electrical tape.

I was actually thinking about aluminum tape. Although, I dont think its the material that is a possible issue, its the adhesive. I am afraid the stuff will ooze over time.

as far as how much. the ONE person who mentioned using tape says he ended up putting on about 3mm of tape. that sounds like a lot, but who knows. anything is worth a shot.

boreas
03-18-2012, 12:27 PM
as far as how much. the ONE person who mentioned using tape says he ended up putting on about 3mm of tape. that sounds like a lot, but who knows.

It does. We're talking about a 4% speed error here so it seems to me (without doing any calculations or testing at all) that changing the circumference of the inner platter by 4% would at least get you very close.


So, you'd take the diameter of the inner platter and multiply by Pi (3.1416) to give you the circumference.

Then multiply that figure by 1.04.

Divide that figure by Pi to get your new diameter.

Subtract the "old" diameter from the new.

Divide by two and that gives you the necessary thickness of tape.

I think. ;)

John

keithpgdrb
03-19-2012, 12:52 AM
It does. We're talking about a 4% speed error here so it seems to me (without doing any calculations or testing at all) that changing the circumference of the inner platter by 4% would at least get you very close.


So, you'd take the diameter of the inner platter and multiply by Pi (3.1416) to give you the circumference.

Then multiply that figure by 1.04.

Divide that figure by Pi to get your new diameter.

Subtract the "old" diameter from the new.

Divide by two and that gives you the necessary thickness of tape.

I think. ;)

John

wow, thats a lot of math.

keithpgdrb
03-22-2012, 11:22 AM
Just an update, and interesting results. I ended up just giving up on the idea of changing the cap. Pretty much everyone said it wouldn't do anything, and I got really busy. I may change it later.

So, I taped the platter with electrical tape. Not thrilled, but it did work. I actually have a play along record where the first track is a tuning note. I fed the audio into my digital chromatic tuner. Pretty much sits dead in tune now.

Interestingly enough, I did this with the old wider thinner belt. When I installed the newer belt, the table went way too fast. By a half step almost. Very interesting because they are both supposed to be pl50 belts, and are the same length. So it seems the wider belt made the change with the tape, while the newer narrower thicker belt pretty much hardly changed the pitch at all. The new belt also fits tighter.

So anyway, I'm going to try to return the new belt, and then I'll struggle when this one wears out. I can see why some people hate belt drives.

One side note. It is indeed amazing how much the sound opens up when it's at the correct speed. Everything is fuller and richer. This is what I was hoping for.

Metalownz
06-20-2012, 11:24 AM
I had this issue with my newly owned PL-50 running too fast, and i just unscrewed the pulley that the belt wraps around, pushed it down till the belt was close to the top, then tightened the screws, problem solved. ;)

jimbofish
06-20-2012, 11:54 AM
It does. We're talking about a 4% speed error here so it seems to me (without doing any calculations or testing at all) that changing the circumference of the inner platter by 4% would at least get you very close.


So, you'd take the diameter of the inner platter and multiply by Pi (3.1416) to give you the circumference.

Then multiply that figure by 1.04.

Divide that figure by Pi to get your new diameter.

Subtract the "old" diameter from the new.

Divide by two and that gives you the necessary thickness of tape.

I think. ;)

John

Your geometry is right. :yes:

Math-wise, though, I believe you can simplify the calculations by just multiplying the original diameter by .04 and dividing by 2. :scratch2: Some of the calculations can be canceled out algebraically.

SoundsRight
06-20-2012, 01:53 PM
When needing to measure RPMs accurately I would recommend getting an RPM meter (tachometer). They can be very cheaply purchased on Ebay and work well. There are non contact types using a laser diode and read RPM by placing a small piece of reflective tape on the platter or disc and pointing the laser at it.

Here is one similar to the one I got:

Digital Tachometer (http://tinyurl.com/cyosc3u)

Just search Ebay for "Digital Tachometer" there are many suppliers. They work well and are cheap.

What I did was get an old LP I did not like and on one side I put a single reflector piece to measure RPM, and on the other side of the LP I put 10 reflectors precisely spaced at 36 degrees. Using the 10 reflector side the meter reads the RPMx10, so just divide by 10 for an improved average and double digit accuracy.

Maybe I can post some pictures later.

SoundBound (http://www.soundbound24.blogspot.ca)

ukfan4sure!
11-22-2013, 08:15 AM
Change the belt. I've worked on a lot of turntable and, in my experience, 9 times out of 10 changing the belt will correct the speed problem. Small variations in belt diameter, width or thickness can cause the speed to be off. It helps to have a stock of belts available to try to find the one which works right. I have to do this on a regular basis. How wide is your replacement belt? Most Pioneer turntables want narrow belts (around 0.185") but many vendors sell ones of 0.2"-0.25" width and claim they are the right ones.
Rick

For everyone out there buying replacement belts off of that famous auction site, this bit of advice is spot on. I have also experienced this problem with belts purchased.

When I told the seller of the belts about the THICKNESS (not width in my case as Rick reports above) problem, he told me basically I was nuts, but did a refund to avoid a conflict. I wasn't even asking for that. I was simply telling him his belts didn't meet spec and would cause it's intended turntable to run fast. He needed to be aware of that. His belts measured at 0.032 inches and spec on the old belt (the original) showed 0.024 inches.

The problem is, the platter speed is based on the effective diameter of the pulley/belt combo. If the belt is thicker, it adds to the total ratios. Trust me, it's true! Here is an exerpt from a posting on Audio Asylum from a while back.

"...As I understand it the rotational speed is a function of the size of the pulleys and the belt thickness. This is because, contrary to what you might think is logical, the length of the belt has to be measured at its center of thickness. Think of bending a rubber tube around something round. The inner diameter will compress and the outer diameter will stretch.

There's a name for this phenomenon, but I can't think of it. I think that when mechanical engineers are spec'ing pulley's there is a formula that takes into account the belt thickness and compensates. That little bit of compression will affect the turning ratio of the pulleys.

Think that if you have two pulleys of the same size it would not matter what the thickness of the belt is. But if two different size pulleys their different diameters will affect the amount the amount of compensation that has to be calculated...."
.

Sprague
03-11-2014, 02:42 AM
just bought one of these (4,000 yen I couldnt very well just leave it in the shop)

http://audio-database.com/PIONEER-EXCLUSIVE/player/pl-50l.JPG