Pioneer PL 50 runs too fast
- Thread starter keithpgdrb
- Start date
keithpgdrb
Super Member
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
Luddite Tendencies
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?
I'd like the answer to this also. Anyone ever change this out - and get positive results?
boreas
"If it sounds good, it IS good." E.K.E.
Bigger drive element (capstan) = faster. Bigger driven element (platter) = slower.
John
keithpgdrb
Super Member
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
Super Member
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.
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.
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keithpgdrb
Super Member
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
Super Member
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
Super Member
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.
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
Super Member
qpagoda
Super Member
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.
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
Super Member
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.
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
Super Member
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 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
Super Member
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
the brandy coffee man
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 .
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
New Member
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.
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
Super Member
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.
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
Super Member
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?
I may try it this weekend. Any idea how thick a layer it requires?
boreas
"If it sounds good, it IS good." E.K.E.
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
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GreatTone
Super Member
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.
