Vintage HiFi Audio Forum
Repair / Help Forum => Repair / Help => Topic started by: EmperorNorton on November 05, 2018, 10:00:22 AM
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Hey folks
Bought a new 23.6"belt for this Sansui turntable I found few months back. Put a few drops of oil in the tube under the platter and its runs very nicely apart from the fact that it plays a half step fast. I played Ella and Louis 'April in Paris' on CD which is in B flat but when I play the LP it in B. Probably not noticeable to 95% of the population but I'd like to sell it as 100% perfect.
One person I read online said that making the platter a little bigger with DymoTape (which might be scrce these days) would do the trick. Might just try a couple layers of all purpose duct tape.
Any thoughts from the turntable gurus?
Thanks in advance.
Mike
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In theory that should work, but in practice I hate it as a "solution" (FWIW, I'm no guru). I would think that the motor has something in the circuit which is drifting out of spec. If that's the case, you may end up adding tape every few months as it continues to drift until it finally fails. If it were me, I would start with recapping the power supply then doing whatever the manual says to fine tune the speed. I would be very surprised if there isn't a a trim pot somewhere on the power supply.
Is it off in 45 RPM as well or just 33? That may help to narrow down the issue.
I just checked, there is a service manual on VE.
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Its slightly off at 45 also.
I have read that there are not speed adjustments on his model.
there is slight chance the belt is too wide but, while it is obviously not a long term permanent fix, I am planning to sell it and don't want to invest any money into it by taking it to Vince for(possible) repair. If it is an issue with the belt and not the motor, I'd reckon adding a bit of very hard material, like the DYMO Tape mentioned in one of the forums I read, would last a long long time. Duct tape, probably not so much.
I suppose I can sell it as-is, giving the buyer heads up about the speed issue, obviously.
Decisions, decisions....
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I took a look at the service manual...it it 90% about the automatic arm movement. In the troubleshooting section:
Problem: Incorrect speed
What to do:
Improper capstan
Improper setting of capstan
Dirty capstan
Stretched belt
You could try and clean the capstan, but in my opinion it's the belt. The correct belt is likely unobtanium in the exact tolerances it needs to be. This is likely why the tape on the spindle is the best available fix. While it's not the most elegant fix, if it were mine I'd add the tape.
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According to the specs it has a synchronous motor so the speed should be controlled by the 60Hz 120 VAC input. If it is set for European 50Hz frequency it would run fast being powered by 120VAC 60Hz. Check and set if it can be re-wired or switched to 60Hz setting.
I think putting tape on the platter is a bad idea. It will add a lot of wow and flutter to the output signal.
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I think putting tape on the platter is a bad idea. It will add a lot of wow and flutter to the output signal.
I agree. I'm not sure that the 50Hz/60Hz is the culprit, because that would be about an 18% difference, and I'm sure a half step is far less than 18%. That said, I like the notion that brown power could be the culprit. Lots of fancy tables use outboard speed controls. Do you power condition? Do you have a gauge to say exactly how many volts you are running at? Perhaps you could measure the speed at peak usage and late at night when usage is down and see if there is a difference. There is a great app for Android called RPM Speed and Wow which you can use to measure. If you are one of those iGuys I am sure they also have a similar app.
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If the motor speed is controlled by the 60hz frequency, it doesn't seem a voltage drop should affect it (unless maybe it's extreme). Might be a motor cap or two going out of spec. Bad caps almost always seem to be the culprit when my tape machines run fast.
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If the motor speed is controlled by the 60hz frequency, it doesn't seem a voltage drop should affect it (unless maybe it's extreme). Might be a motor cap or two going out of spec. Bad caps almost always seem to be the culprit when my tape machines run fast.
That would also be my 1st component-of-interest. Be it cassette decks or turntables, bad caps in the motor electronics make them behave in wacky ways - I have seen turntables rotate in the opposite direction. Are the 0.22 and 0.033 uf caps measuring ok?
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Emp, do you know which capstan you have? Those tables shipped with two different capstans, one for 50 and one for 60hz.
Not arguing against the idea the caps are to blame, but what if they're not? Found a few posts about those early 70's Sansui's, none mention caps. Most mention the tape idea, hanging the belt with a weight to stretch it a tad, and one that puts nail polish on the capstan to thicken it up a bit. Either way, Im interested in hearing what solves it.
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Might just drive out bethel park way, but in the meantime , perhaps order a
Little bigger belt, this one seem pretty tight. I'm new to this stuff but it seemed tight.
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Emp, do you know which capstan you have? Those tables shipped with two different capstans, one for 50 and one for 60hz.
Again, that would be a 17% difference, which would translate to almost a step and a half in musical terms. If Emp is correct about it being a true half step off, the 50/60 issue couldn't be the cause. I suppose it could be the belt, but feel caps are far more likely. Plus, it's a good thing to do to a 40 year old piece of electronics anyway. If you spend a few bucks and a couple hours on caps and it doesn't correct it, you still haven't done any harm.
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Emp, do you know which capstan you have? Those tables shipped with two different capstans, one for 50 and one for 60hz.
Again, that would be a 17% difference, which would translate to almost a step and a half in musical terms. If Emp is correct about it being a true half step off, the 50/60 issue couldn't be the cause. I suppose it could be the belt, but feel caps are far more likely. Plus, it's a good thing to do to a 40 year old piece of electronics anyway. If you spend a few bucks and a couple hours on caps and it doesn't correct it, you still haven't done any harm.
How dare you kill an argument with MATH!!! :)
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Emp, do you know which capstan you have? Those tables shipped with two different capstans, one for 50 and one for 60hz.
Again, that would be a 17% difference, which would translate to almost a step and a half in musical terms. If Emp is correct about it being a true half step off, the 50/60 issue couldn't be the cause. I suppose it could be the belt, but feel caps are far more likely. Plus, it's a good thing to do to a 40 year old piece of electronics anyway. If you spend a few bucks and a couple hours on caps and it doesn't correct it, you still haven't done any harm.
How dare you kill an argument with MATH!!! :)
It seemed like nobody heard me THE FIRST TIME I said that, LOL.
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Might just drive out bethel park way, but in the meantime , perhaps order a
Little bigger belt, this one seem pretty tight. I'm new to this stuff but it seemed tight.
Wife and kids are in Disney til next Friday and I'm mostly home getting some work done. Just give me a heads up if you want to bring it out this way.
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Update time.
Picked up a Sanyo turntable today. It was belt drive so I put the Sanyo belt on the Sansui and the speed is now 34 RPM . My conclusion is that the belt they sent me for the 4060 is too small. Plan to find local place that sells belts and take the Sanyo belt and find a belt jut slightly larger than the Sanyo belt.
Thanks for everyones suggestions.
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Great. I would still recommend using the app to check wow and flutter.
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Put some 240 grit wet or dry sandpaper to the capstan----& check speed as diameter of capstan decreases----when you are there, polish it with some 600 grit wet or dry. That's really a pretty small "error" & sometimes the 60 cycle 110 volts in your area may not be right on. Street voltage & cps (hertz) also varies quite a bit---depending on location & lenght of "drop". Try it somewhere across town, and see if it reads the same.-----Rik
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I got curious about our Power Company 60 Hertz variations---& here's what I found----Verrrrry interesting From "Mike Holt's Forum"-----
:http://www.ornl.gov/sci/btc/apps/Res...NLTM200341.pdf was fascinating . It looks like +-0.01Hz is the normal operating range, with +-0.02 Hz intentionally used to adjust long term averages.
Evidence of long term (over the course of a month) errors on the order 0.004Hz is enough to get some people worried about the grid.
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.024 Hertz error divided by 60 hertz = .004 %----approx 1/2 of 1% fluctuation in 60Hertz voltage from power companies
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Turntable rurning at 34rpm is .666 rpm fast---divided by 33 1/3 (33.333) =.o199 %----Approx 2% fast
Lets say a 3 /12 minute recording----Thats 210 seconds times ..02 (2%) = 4.2 seconds
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I believe this would be just within factory "specs" for an "average turntable" with no speed adjustment---I think only a pro musician or a "Guru Audiophile" might be able to pick up on this----without an instant comparison for a "pitch" comparison. I have a couple of turntables with speed adjustment, & never do they read the same with a strobe & disc---sooo, It could be power line "Hertz"---or who knows what changes take place. I had nothing better to do tonight---I hope I didn't bore you---LOLOL !!!!!
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CORRECTION to the above post------I hadn't noticed & taken into consideration that the .01 Hertz was a "plus or minus" number---sooo---that doubles the "spread---and the .02 hertz average adjustment correction number is also "plus or minus"----doubling the spread---soooo----the total fluctuation of 60 hertz could be as high as one percent. Now I know why I always had to adjust the speed controls on my speed control turntables---probably changes from day to day, when they "shift" the power from Gas, Oil, coal fired & hydro electric turbine generators, for maintenance & repair, etc.---Also, I had a typo---- I meant 3 1/2 minute recording---210 seconds.--sorry----Why did I have to wait all these years to figure this out ????---LOLOL-----One percent variation in 60 Hertz is not good for turntables or recorders.---Imagine a recording studio trying to "mix tracks" if one was coming in digitally from a different location?---I'm sure they do it all with the same power supply.