I'm hoping someone can point me in the direction of an answer to this query. My 401 has a thump which is audible. The thump occurs once every revolution (regardless of speed). Would I be right in thinking it is something to do with the platter rather than the idler? If the idler had a flat spot, that would be apparent more than once per revolution?
Any advice gratefully received.
Gary
401 thump
#4
Hi Gary.
Remove the platter and check the inside rim for any kind of damage, including fractures, corrosion, dirt, flat-spots or eccentricity. Could the platter have been dropped? Has it done this since you had it, or is it a recent occurrence? Could the brake be catching on something maybe?
Is there any visible movement in the platter as it rotates either on the horizontal or vertical plane (i.e., does the gap between platter and chassis alter anywhere when looking from the side or does the platter look as though the rotation is eccentric when viewed from above)?
It might also be worth removing the main bearing from the chassis, stripping it down and examining the innards (good chance to give it a thorough inspection, check the spindle for trueness and lube it all up too).
If it is only making this thumping noise once per revolution regardless of speed, it HAS to be something to do with either the platter, the main bearing or the interface of both.
Good luck,
Cheers
Remove the platter and check the inside rim for any kind of damage, including fractures, corrosion, dirt, flat-spots or eccentricity. Could the platter have been dropped? Has it done this since you had it, or is it a recent occurrence? Could the brake be catching on something maybe?
Is there any visible movement in the platter as it rotates either on the horizontal or vertical plane (i.e., does the gap between platter and chassis alter anywhere when looking from the side or does the platter look as though the rotation is eccentric when viewed from above)?
It might also be worth removing the main bearing from the chassis, stripping it down and examining the innards (good chance to give it a thorough inspection, check the spindle for trueness and lube it all up too).
If it is only making this thumping noise once per revolution regardless of speed, it HAS to be something to do with either the platter, the main bearing or the interface of both.
Good luck,
Cheers
©2020 Lee
#5
Hi Lee, good advice,
A little background...
The bearing has only just left here after being stripped down and checked over. It was found to have exceptionally good bearing sleeves and therefore we advised not to change them. The shaft was in equally good condition.
The only change that was made was fitting a ceramic thrust bearing.
There are only two things that go around with the platter in synchrony, the platter itself and the bearing.
The only other thing I can think of right now is the alignment of the idler wheel. We have seen these off the 90 deg angle due to badly machined idler housing castings in the past. Every so often the idler "jumps" as it turns.
maybe in this case once every revolution? It is usually more often.
A little background...
The bearing has only just left here after being stripped down and checked over. It was found to have exceptionally good bearing sleeves and therefore we advised not to change them. The shaft was in equally good condition.
The only change that was made was fitting a ceramic thrust bearing.
There are only two things that go around with the platter in synchrony, the platter itself and the bearing.
The only other thing I can think of right now is the alignment of the idler wheel. We have seen these off the 90 deg angle due to badly machined idler housing castings in the past. Every so often the idler "jumps" as it turns.
maybe in this case once every revolution? It is usually more often.
#6
What about spinning the platter by hand ?
Unplug the power and use the on switch a bit to disengage the platter brake and see if it makes the thump when the idler is not rubbing on the platter.
Unplug the power and use the on switch a bit to disengage the platter brake and see if it makes the thump when the idler is not rubbing on the platter.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#7
Lee, thanks for the trouble you have taken.Lee S wrote:Hi Gary.
Remove the platter and check the inside rim for any kind of damage, including fractures, corrosion, dirt, flat-spots or eccentricity. Could the platter have been dropped? Has it done this since you had it, or is it a recent occurrence? Could the brake be catching on something maybe?
Is there any visible movement in the platter as it rotates either on the horizontal or vertical plane (i.e., does the gap between platter and chassis alter anywhere when looking from the side or does the platter look as though the rotation is eccentric when viewed from above)?
It might also be worth removing the main bearing from the chassis, stripping it down and examining the innards (good chance to give it a thorough inspection, check the spindle for trueness and lube it all up too).
If it is only making this thumping noise once per revolution regardless of speed, it HAS to be something to do with either the platter, the main bearing or the interface of both.
Good luck,
Cheers
There are some 'dings' inside the platter, but it's hard to tell if any of these are the cause since I don't know where abouts the idler interacts with the platter. Any advice?
There isn't any visible movement in the platter as it's revolving in either plane, so I don't think it's out of true.
As Darren has already responded, the spindle & bearing is just back from Slatedeck after being checked & having the new thrust bearing fitted, so I don't think that's the culprit.
Gary
#8
Marcus, the thump before was just audible if I listened close to the deck. I did what you suggested, and it changed from a thump to a ringing, so it seems something, somewhere on the periphery of the platter is hitting on the deck. Any ideas on how to determine where this is happening?pre65 wrote:What about spinning the platter by hand ?
Unplug the power and use the on switch a bit to disengage the platter brake and see if it makes the thump when the idler is not rubbing on the platter.
Gary
#9
Hi-i don't want Darren to take offence on this suggestion but i had a similar problem some time ago with a Lenco idler drive turntable where the bearing thrust washer,for some reason,was thinner than it should be and letting the platter sit a gnats lower than it would normally do.
Might pay you to check there are TOTALLY clean and smooth surfaces between the bearing housing and top plate.
Might pay you to check there are TOTALLY clean and smooth surfaces between the bearing housing and top plate.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
#10
No Offense taken Philip, and a good point too.
Different turntables of the same model can have slight variations and as Philip suggests you may want to check that the platter is indeed high enough.
Gary, can you explaine the dings in the platter a bit more clearly, maybe a picture. If you can't post one here just send it to my email add.
Different turntables of the same model can have slight variations and as Philip suggests you may want to check that the platter is indeed high enough.
Gary, can you explaine the dings in the platter a bit more clearly, maybe a picture. If you can't post one here just send it to my email add.
#14
Darren, the link is to a couple of photos of the 'dings'. The second is a bit out of focus, but should give some idea.Darren wrote:No Offense taken Philip, and a good point too.
Different turntables of the same model can have slight variations and as Philip suggests you may want to check that the platter is indeed high enough.
Gary, can you explaine the dings in the platter a bit more clearly, maybe a picture. If you can't post one here just send it to my email add.
http://imageupper.com/g/?S060001010I2079991772025928
Gary
#15
Hi-if that were mine,i would take a file to those "dinks" (not on the inner edge where the idler runs) and just clean them up.
It may be the "gnats whatsit" that is causing your problem.
It may be the "gnats whatsit" that is causing your problem.
The only thing necessary for the triumph of evil is for good men to do nothing.
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)
Edmund Burke
G-Popz THE easy listening connoisseur. (Philip)