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Direct Drive Turntable Thudding Noise When Spinning

Isaac C.

Isaac C.

Cat Hoarder
Hello everyone, attached is an audio file of my turntable making a thudding noise as it spins. This was recorded with a microphone held directly over the middle of the platter. The speakers do not pick this noise up, but I just wanted to make sure this is not indicative of an issue that might potentially get worse. It is a servo direct drive motor. Thanks in advance! I had to .zip the file so that it can be uploaded.
 

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@tnsilver That was recorded with the receiver off without a record, all I did was turn the turntable on and record the noise coming from the platter.
 
Isaac C. said:
Hello everyone, attached is an audio file of my turntable making a thudding noise as it spins. This was recorded with a microphone held directly over the middle of the platter. The speakers do not pick this noise up, but I just wanted to make sure this is not indicative of an issue that might potentially get worse. It is a servo direct drive motor. Thanks in advance! I had to .zip the file so that it can be uploaded.
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And you're saying the cartridge is not picking it up? Strange...

It sounds too regular to be mechanical. I'd suspect something in the speed control circuitry but I'd think it would affect speed, so maybe it is mechanical. A dirty bearing, maybe?

Strange....
 
WaynerN said:
It certainly is related to the platter's rotation!!!! I suspect it might need some lubrication and a look at the thrust washer.
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Quite possibly, but bearing noise tends to sound like a grinding noise. This sounds more like motor boating to me. Still worth a look at the bearing, though.
 
I had the table serviced this summer because it was spinning way too fast. The main PCB has also been recapped as well. I might take it back to the gentleman who fixed it to see what he thinks, he has been working on audio equipment for more than three decades. I just wanted to check here before taking up his time in case it was something simple.
 
Also it does not make this noise when it is spun by hand and the "thudding" occurs faster when switched to 45.
 
Isaac C. said:
Also it does not make this noise when it is spun by hand and the "thudding" occurs faster when switched to 45.
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Yep, definitely a speed control issue, then.

I have no idea where to look on the board, but your tech should have some idea. If the speed is alright, I'm guessing the motor coils are not being pulsed correctly, like badly timed cylinders, even if the rpm is right.

Good luck with it. I'd like to hear what you learn.
 
@ripblade Thanks for the reply, I'll likely take it Friday, hopefully it won't be a troublesome fix. When I watch the strobe, the speed stability is not that good, it seems like its struggling to compensate for the speed loss or gain. It almost seems like its over correcting, then braking very harshly to slow it back down, resulting in pretty high wow and flutter.
 
I got the table looked at today, unfortunately there is nothing I can do about the noise since parts for this table are non-existant. The gentlemen who repaired it a few months ago said the bearing was a bit worn and that was what causing the noise. He does not think it will get worse any time soon, so thats good.
 
Not sure if it could be the same on your table but I had a Technics of some sort once that would make a quiet but still annoying "creak-tick!" once a rotation. I couldn't for the life of me figure out what was causing it until I took the platter off and noticed that there were several wedge shaped bits making up the motor parts. Surmising that one could possibly be loose I pushed on each a bit, put it together and retried it. The noise stopped for a few minutes and then started up again. I gave the table to a friend so can't say that a dab of glue would have fixed it but it very well might have.
 
I noticed when I took the spindle/ subplatter assembly out that the ball bearing at the bottom of the spindle thats sits in the bearing well has a flat spot. Could this be the issue?

Also there is no horizontal movement of the spindle in the bearing.
 
Also there are some plastic (Nylon?) washers, do they go on top where the green oval is, or at the bottom between the bearing and c-clip? They were on on the bottom. The spindle is currently being held up by the bearing well cap so that it doesn't rub the speed sensors, thats why I was wondering if the washers go on top so they support the subplatter rather than the bearing well cap. Could it be that the worn ball bearing is causing the noise since it has weight on it, or is that the way its designed?
 

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tnsilver said:
I'd leave the washers where I've found them. What are the odds some munchkins got inside and tampered with them? I believe they're there for damping any metal to metal contact noise. I'm not aware of ball bearings that are made with a flat spot for use in bearings but then again, ball bearing at tips of spindles are there for the minimization of the contact point with the thrust plate and they're not usually designed to turn. Who knows... You could measure the diameter with a caliper and order a new ball for some change. Ceramic, tungsten, stainless steel balls, whatever... Experiment and see.

BTW, is there a reason you seem to keep the turntable model and make obscured while asking for this technical help? Is that the Sanyo from your sig?
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Yes, I didn't mention it because not many people are familiar with it.

@Mr Boochie no there isn't. That's why I'm trying to determine if it's mechanical or electrical. If I can't get it fixed that's fine, but I just want to make sure nothing is going to get worse.
 
Is this table semi automatic? It almost sounds like gear noise for the auto return not being completely disengaged.
 
I recapped the main pcb before I took it to him, I still have the three psu caps I need to replace though, just haven't had time. Could that help?

If I remember correctly I have a 1000mf, 100mf, and 10mf cap to replace on the PSU pcb.
 
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