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Turntable problem

Old 02-02-10, 01:36 AM
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Turntable problem

I have a not-too-old Pioneer stereo system with a turntable, and I haven't used the turntable in a few years. I tried to play an album for someone around that time, and the turntable wouldn't play. It had power, because I could hear the scratching come through the speakers when I lightly dragged my finger across the needle. It just wasn't spinning. I said oh well and just left it.

I decided to take it apart recently and figure out what was wrong with it. It didn't take long to determine that the belt had snapped because of the long-term heat from my surround sound unit I had the turntable sitting on. I got a new belt from someone on eBay, put it in, and put an album on. Right away, I could tell that there's something else wrong, because I'm getting a kind of "warping" effect. It's hard to describe, so I recorded it:

<object width="425" height="344"><param name="movie" value="http://www.youtube.com/v/dN6LHpPD2-c&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="http://www.youtube.com/v/dN6LHpPD2-c&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="425" height="344"></embed></object>

Has the motor gone bad, or is there something that can be done, like maybe a drop of oil down into it? Could it be the belt I just got? It seemed to fit okay, but it's not extremely tight. Is it supposed to be fairly tight?
Old 02-02-10, 11:33 PM
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Re: Turntable problem

Bumping for help.
Old 02-02-10, 11:40 PM
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Re: Turntable problem

Video is private but if the belt is not tight enough, it could cause slipping causing what you are describing. Also, you might have to make an adjustment to one of the precision speed trim-pots to get an accurate 33 1/2.
Old 02-03-10, 12:02 AM
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Re: Turntable problem

Sorry. Didn't realize the video was private. Should be fixed now.
Old 02-03-10, 01:20 AM
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Re: Turntable problem

Yeah, definitely an issue with speed variations; do you have to exert a lot of force to put the belt over the drive spindle? If you do, then it's too tight of a belt. It's hard to be definite as to whether it's slipping and causing a drop in speed or it's too tight and causing it to speed up.

If you are certain that you have the correct belt, then I would go the route of adjusting the speed precision trim pots. On my Sansui Direct Drive, I have them accessible from the bottom, which requires a jig of sorts in order to prop up the turntable and to be able to see the strobe pattern, indicating that it's at the correct speed. One thing of note is that when you use regular lighting for the pattern, the frequency of the electricity is not constant so you aren't going to get a completely accurate adjustment but it should allow you to figure out if there's more behind the troubles.

Here's a link for a strobe disk pattern; just print it out and place it on the turntable while you're adjusting each speed trim pot and when the corresponding pattern stops, you've got it. http://www.extremephono.com/free_tur...trobe_disk.htm Oh, do you happen to have a model number for that Pioneer? If it's more than just adjustments, you might have a fault with electrolytic capacitors falling out of spec.

Last edited by gmanca; 02-03-10 at 01:25 AM.

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