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Is there a TT bearing expert in Vic? the Luxman beckons..


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I thought the bearing was "not part of the problem". How can one be confident of success yet? Did I miss something? Still reckon the motor is dodgy myself. :)

Yes, I think you "missed something", Jake! ;)

Stuart fixed the "motor problem". The drive IC still ran away and the speed increased. He posted that he could get this effect to happen, simply by heating up the IC with a hair dryer.

That says to me that something was causing the drive IC to work overtime, so it got hot. It makes sense to me that bearing friction could have caused this - the speed was slowing ... so the drive IC was working overtime to increase speed ... so it got hot. Remove the friction ... and the drive IC doesn't have to get hot ... so the speed remains constant.

Why the friction - it would seem old, dirty oil?

Regards,

Andy

Yes, I read all that. But initial inspection of bearing showed no problem. But fault cannot be replicated now, so despite bearing being ok, everyone celebrating. Still think I missed something.
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I have now been spinning records on my lazarus-like Luxman for about 6 hours...It has been rock solid, not a waver, not a hint of speed anomaly. And...It sounds wonderful! Unbelievable I know but thi

Hi Unclemack, Nice turntable the Luxman PD 350, too good to scrap. I'm based in Nowra NSW and can arrange free shipping from Southern Cross and return by coach, Premier Motor Service. Send it up an

Well, It's all packed up and on the way to Vince... I am cautiously optimistic.   Cheers   M

Yes, I read all that. But initial inspection of bearing showed no problem. But fault cannot be replicated now, so despite bearing being ok, everyone celebrating. Still think I missed something.

 

As you say, initial inspection of the mechanical wear on the bearing showed no problem.  But I could imagine that dirty oil would have a negative effect - hindering the smooth rotation and so causing the drive IC to have to work harder.

 

 

Regards,

 

Andy

Edited by andyr
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Yes, I read all that. But initial inspection of bearing showed no problem. But fault cannot be replicated now, so despite bearing being ok, everyone celebrating. Still think I missed something.

As you say, initial inspection of the mechanical wear on the bearing showed no problem. But I could imagine that dirty oil would have a negative effect - hindering the smooth rotation and so causing the drive IC to have to work harder.

Regards,

Andy

Well, that must be some intolerant IC then.
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Some thoughts on turntable speed control.

Turntables driven by a DC motor usually incorporate a closed loop feedback control system. The design parameters of the controller allow for a range of variables within the motor, pulley, belt, platter and bearing system. If any of these variables e.g. bearing friction, exceeds the expected parameters then the control system may not be able to maintain stability and may even enter a chaotic state. The extent and period of the random variations depends on the type and gain of the feedback. Bearing friction is not an obvious or intuitive cause of erratic speed but should always be considered in diagnosing problems. Removing all traces of old, contaminated lubricants, thoroughly cleaning bearing surfaces and replacing the lubricants with high quality products can work miracles with your turntable speed control and improve the sound as a bonus.

Best to all,

Vince

Edited by Once Analog
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Hi Duc,

Maybe, 36 hours now and speeds still stable, will continue to monitor.

Vince

 

Hi Vince .

i would call it a success mission .actually  i'm very surprise  the problem was caused y the bearing. i never have thought the bearing cause speed problem. i only recommend clean/checking  the bearing for the sake of it but never hope it will solve the problem , i suppose we live and learn :P

cheers

Duc

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58 hours pass, Luxman speeds still stable, hmm.

Not ruling out some intermittent problem that hasen't surfaced?

Like UM said, this Luxman has tricked others!

I think we can say the motor is not an issue.

Vince

Edited by Once Analog
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Luxman Bearing Service Difficult

The Luxman bearing is held in place with a 55mm Hex nut and someone had used "Loc Tite" on the thread!

I lost 2 hours removing the bearing housing. How was it done? I removed the platter support bracket and submerged the nut in a saucepan of boiling water.

The oil was the worst condition I have ever seen!

Vince

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Luxman Bearing Service Difficult

The Luxman bearing is held in place with a 55mm Hex nut and someone had used "Loc Tite" on the thread!

I lost 2 hours removing the bearing housing. How was it done? I removed the platter support bracket and submerged the nut in a saucepan of boiling water.

The oil was the worst condition I have ever seen!

Vince

Would this have been done during manufacturing?

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The drive IC still ran away and the speed increased. He posted that he could get this effect to happen, simply by heating up the IC with a hair dryer.

Regards,

Andy

Quite common Andy.

After applying the hair dryer trick to heat up the IC, giving the motor erratic behaviour, it should have been followed up with swabbing the IC with methylated spirits which would pull the heat from the IC very effectively.

Monitoring the motor speed. Repeated several times would have given the IC pattern? If constant, would have shown the IC is sensitive to temperature change and show the IC had a problem, even though changed.

My next test.

Vince

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Also Noted:

I have been running the Luxman, (trouble free) without the bottom cover. Underneath the Luxman is a confined area, the metal sealed cover, with the exception of the phono cable hole, (back right hand corner) has NO vented holes, especially above the cct board - do we have an oven here effecting the IC?

Vince

Edited by Once Analog
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There's only on e way to tell, keep in mind that the Luxman has been this way new out of the box, new, it hasnt had a problem until now!t

 

 

Yes, you would think that an oven effect would point to a design flaw which very quickly would have been discovered and well documented. Still, this TT has done things most other TTs have not!

 

Cheers

 

M

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Hi UM,

Some further progress, heat was applied to the motor without any affect, (no change in motor RPM),I think the motor is ok.

Applied heat to the ICs and a different story, motor speeded up, but swabbing with Metho reduced the motor (RPM. Sensitive to temperature change).

Set the potentiometer presets, so now the exact speeds are correct, in the centre of adjustment.

Also, the belt supplied is it an original "Luxman"? The platter/motor/pulley and drive belt are a designed system, not individual components.

Vince

Edited by Once Analog
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Luxman Bearing Service Difficult

The Luxman bearing is held in place with a 55mm Hex nut and someone had used "Loc Tite" on the thread!

I lost 2 hours removing the bearing housing. How was it done? I removed the platter support bracket and submerged the nut in a saucepan of boiling water.

The oil was the worst condition I have ever seen!

Vince

I hate that Loc-Tite muck. More trouble than what it is worth IMO. I have it at my work and I only use it only sparingly and reluctantly!

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"is there a TT bearing expert in Melbourne?"

I suspect the reason your getting few responses to your exact question is- would I offer the name of a skilled technician to solve this problem?

I could well become their worst enemy over night.

10 -20 house hundreds of dollars and no result

I notice the couple of experts who frequent this site from Melbourne are keeping their collective heads down

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"is there a TT bearing expert in Melbourne?"

I suspect the reason your getting few responses to your exact question is- would I offer the name of a skilled technician to solve this problem?

I could well become their worst enemy over night.

10 -20 hours hundreds of dollars and a strong possibility of no result

I notice the couple of experts who frequent this site from Melbourne are keeping their collective heads down

No not a reference to Zaph who weall know has 2 heads- he lives in NSW

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I hate that Loc-Tite muck. More trouble than what it is worth IMO. I have it at my work and I only use it only sparingly and reluctantly!

Its how when and where you use it! There are also different types and strengths. Use it the wrong way and you have Vince on your back!

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Hi UM,

Some further progress, heat was applied to the motor without any affect, (no change in motor RPM),I think the motor is ok.

Applied heat to the ICs and a different story, motor speeded up, but swabbing with Metho reduced the motor (RPM. Sensitive to temperature change).

Set the potentiometer presets, so now the exact speeds are correct, in the centre of adjustment.

Also, the belt supplied is it an original "Luxman"? The platter/motor/pulley and drive belt are a designed system, not individual components.

Vince

In regards to your last sentence Vince, I'm not sure that it matters too much in regards to the drive belt.

I replaced the original belt on the PD350 I owned, with an after market belt.....and it was fine for the remaining 4 or 5 yrs I had the table.

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Luxman, Platter Rotational Accuracy:

Using a "Mitutoyo" Dial Indicater, the following measurements were made:

Axial Runout: .004", Runout On Diameter: .002", Spindle: .001"

Compared the above with the OA:

Axial Runout: .003", Runout On Diameter: .001",Spindle Runout: .002".

In my view both perfect!

Vince

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In regards to your last sentence Vince, I'm not sure that it matters too much in regards to the drive belt.

I replaced the original belt on the PD350 I owned, with an after market belt.....and it was fine for the remaining 4 or 5 yrs I had the table.

In a belt driven turntable, belt dimensions are the utmost importance; length, width and thickness (elasticity) are crucial in determining a given turntable's problem. Without the original belt, designed by the maker, any diagnosis is pointless!

Example: if the belt is too short it will increase speed and bearing wear, (side way force). If too long, will slip and speed will be slow. The correct belt length should be a loose fit without slipping.

A "Soundfan" should know this!

Vince

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In regards to your last sentence Vince, I'm not sure that it matters too much in regards to the drive belt.

I replaced the original belt on the PD350 I owned, with an after market belt.....and it was fine for the remaining 4 or 5 yrs I had the table.

In a belt driven turntable, belt dimensions are the utmost importance; length, width and thickness (elasticity) are crucial in determining a given turntable's problem. Without the original belt, designed by the maker, any diagnosis is pointless!

Example: if the belt is too short it will increase speed and bearing wear, (side way force). If too long, will slip and speed will be slow. The correct belt length should be a loose fit without slipping.

A "Soundfan" should know this!

Vince

Lets be realistic here Vince.

You will not find an original belt anymore for this table.

The aftermarket belt I ended up buying worked a treat, so I take some of your comments with a grain of salt. And no..... I didn't just buy any belt and hope for the best, the belt I purchased was meant for use with the PD350.

Give me some credit before lecturing me.....I did own this very table for nearly a decade.

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Lets be realistic here Vince.

You will not find an original belt anymore for this table.

The aftermarket belt I ended up buying worked a treat, so I take some of your comments with a grain of salt. And no..... I didn't just buy any belt and hope for the best, the belt I purchased was meant for use with the PD350.

Give me some credit before lecturing me.....I did own this very table for nearly a decade.

Don't think it was meant to be a personal attack on you personally....Soundfan...

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