401 thump

301, 401, plinths and assorted idler stuff
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pre65
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#16

Post by pre65 »

Where did the dink Emoticon come from ?

I typed the word dink in inverted commas like this "dink" (has it done it again ?)

Automatic Emoticons-whatever next ?
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#17

Post by Darren »

Gary, as bad as those "dinks" look they are not in the idlers path. So prob not your problem. Like Philip though I would clean them up a bit.

"DO NOT" touch the inner surface though..

Make sure they are not touching anywhere as the platter goes around.
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Greg
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#18

Post by Greg »

Gary,

From your description I suspect your platter bottom edge is interfering with the chassis top plate as it rotates. This would explain the ringing (could that be caused by scraping?) as you rotate the platter by hand. I would check you have remounted the bearing exactly as it was at time of removal and if that is right it may well be the thickness of the thrust plate which is the culprit I'm afraid.

Best wishes,

Greg
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#19

Post by Andy831 »

Greg wrote:Gary,

From your description I suspect your platter bottom edge is interfering with the chassis top plate as it rotates. This would explain the ringing (could that be caused by scraping?) as you rotate the platter by hand. I would check you have remounted the bearing exactly as it was at time of removal and if that is right it may well be the thickness of the thrust plate which is the culprit I'm afraid.

Best wishes,

Greg
If the platter was fouling the chassis then the dings may well be the culprit as they seem to hang slightly below the lower rim. I would have thought though that the chassis would have been scratched at the corresponding thump/ding location.
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#20

Post by garyt »

I tried a few things over the weekend - putting white electrical tape on the inside & bottom of the platter to see if it would catch on anything. Nothing, and there aren't any marks on the deck to show if the platter is scraping. It's a bit annoying, as the deck is sounding brilliant, much better than I could have imagined.
There have been some suggestions the spindle bearing housing may not have been refitted correctly. I don't think so, but will take it apart again this weekend & refit to check.
Does anyone have an idea on how to check if the spindle is at the correct height? I think it may be sitting too low down in the bearing housing, causing the platter to foul. If this is the case, I was thinking of fitting a small washer between the bottom of the thrust bearing & the housing cover - this would raise the spindle by the thickness of the washer. Alternatively I could pack the top by putting washers between the top of the bearing housing & the deck. Any ideas if this is feasible?
Gary
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pre65
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#21

Post by pre65 »

Hi-you could put 3 washers between the bearing and base as a temporary measure to see if lifting the platter a couple of mm stops the noise.

Report back with your findings.

NB- the washers are not really a proper cure,just trying to find what the problem is.


PS just been looking at my 401-are you sure the platter is not catching on the strobe chrome surround ? I seem to remember my surround "popped up" a bit some time ago and was catching on the platter. :oops:
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Greg
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#22

Post by Greg »

Hi Gary,

Sorry if I've misunderstood but your latest post seems a little contradictory. Firstly you say (as I understand it) after your experiments there is no sign of any platter/chassis fouling and then you go onto say that you suspect the spindle is sitting too low and may be causing fouling :?

I'd follow Philip's advise. Is anything else near the platter touching it which shouldn't? If you do suspect platter chassis fouling then as suggested, raise the bearing unit with washers and see if you have a solution. If it's a slight interference, one washer per each of the three fixings would do and could be a permanent solution as I don't think such a tweak would change performance in any way. Actually it is doubtful that two or three washers would make any difference to sound.......might even make it better; who knows?

The only other thought I have is if Slatedecks thrust plate is too shallow and with the platter interference seated on the spindle taper, is there any obstruction of platter with bearing housing? Therefore, look about the spindle housing area if you are satisfied there is no interference on the platter's outer and bottom edge. You might need to remove the bearing unit and fit the platter and free spin to examine this.

Best wishes,

Greg
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pre65
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#23

Post by pre65 »

pre65 wrote:Hi-you could put 3 washers between the bearing and base as a temporary measure to see if lifting the platter a couple of mm stops the noise.
Hi-when i said 3 washers, i meant 1 per screw !
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#24

Post by garyt »

Greg/Pre65, thanks for the suggestions. I will remove the spindle bearing from the deck at the weekend, and try the platter on the spindle when removed. That should indictate whether or not the issue is the thrust bearing thickness. If not, then I will reassemble with a washer on each mounting screw. Hopefully that will solve the problem.
I must say the turntable, even with the thump (which is only noticeable between tracks or in quiet parts) is stunning. It easily betters my LP12, so much so that it's going up on epay at the weekend. As soon as I have the thump sorted, I will be one happy bunny :D
Gary
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#25

Post by garyt »

I finally got around to detailed investigation into this issue. I fitted a new plinth to the deck, and tried it out with the only record to hand - a 7" single. Lo & behold, no thump! I thought the change of plinth had cured it, but the first LP I tried, the thump was back. This indicated that there may be something wrong with where the idler rides on the platter at 33 RPM. As I said before, there are a couple of 'dings' in the inside edge of the platter. I put tape on the outside with marks aligning to the dings, and a piece of tape on the deck where the idler is closest when in use. At 33 RPM, the thumps occurred when the indicators on the platter aligned with the indicator on the deck (if you know what I mean). This, I believe, shows the dings are making the noise when the idler hits them. The upshot is, I think I need a new platter. Can anyone point me in the direction of a source?
Thanks in anticipation, Gary
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Greg
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#26

Post by Greg »

Hi Gary,

I've just studied your pictures again and the dings are certainly in the area the idler runs on the platter when played at 33 rpm. However, I think if your idler wheel is contacting the inner platter edge over the dings, it really is lower than it should be. This may well be due to your replacement platter bearing offering a slightly different height from original. I'm not certain at present but I expect the idler wheel height can be adjusted and I know the motor spindle stepped drive wheel can. Coincidentally I will be stripping a deck tomorrow for service so I'll have a good look at the adjustment issues that might be all you need to attend to.

Having said that, there is no need for you to find a new platter unless it has been bashed out of round. File or wet and dry off any high spots around the edge of the dings. Clean the area and then drizzle Araldite into the indentations so it sets proud of the original surface. Then file/rub down to restore the original profile. I guarantee you will not be able to tell the difference from original if you do the job right. Araldite has been used to rebuild motorcycle gearbox sprocket teeth with good results in a similar fashion.

Hope that helps and makes you feel better. I'll come back tomorrow when I have a better overview of available adjustment.

Best wishes,

Greg
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pre65
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#27

Post by pre65 »

Greg wrote:
Araldite has been used to rebuild motorcycle gearbox sprocket teeth with good results in a similar fashion.

Best wishes,

Greg
:shock: :shock: :shock: :?:
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#28

Post by Andrew »

Yes, you can adjust the height of the idler, there's 3 screws on it, just loosen them a tad and gently change the idler position.

-- Andrew
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#29

Post by Darren »

pre65 wrote:
Greg wrote:
Araldite has been used to rebuild motorcycle gearbox sprocket teeth with good results in a similar fashion.

Best wishes,

Greg
:shock: :shock: :shock: :?:
My reaction as well Philip,
Do tell us more Greg?
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Nick
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#30

Post by Nick »

Well, I don;t know about the teeth, it does work for covers certainly, and I can imagine that it would work for chipped teeth, or it might work for sprokets that have been worn by using a worn chain.

Anyway, I think this would work for reparing a platter that was US otherwise.

http://www.amazon.co.uk/Loctite-Super-S ... B0006JJRZ4
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