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Beogram 3000 motor

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scorron
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scorron posted on Thu, Sep 5 2019 2:17 PM

I recently acquired a Beogram 3000 (type 5228, built in 1974) with a motor that barely turned. Using instructions from this forum, I disassembled, cleaned, reoiled and the motor turned normal speed. In fact, it seemed to work perfectly for a few weeks, and now it is having speed problems again. I've read just about everything posted on the subject online, on this forum and others. Has anybody solved the motor problems that plagued these turntables? 

I ordered a rebuilt SP12 (not cheap) and now I don't even know if the turntable will be usable. I certainly can't enjoy listening to it with the speed jumping around. 

Before anybody asks, the belt is new, the idler rubber soft, all parts have been cleaned and reoiled/greased, switches cleaned with 1000 grit sandpaper. 

 

Thanks in advance,

Sean

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Dillen
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These are typical symptoms of bearings not being oiled the right way.

Did you infuse the oil using vacuum etc. or did you merely add drops of oil to the bearing?
Which type of oil did you use?

Oh, and don't clean switches with sandpaper. It does permanent damage to the extremely thin platinum layer on the switch contacts.
Use a piece of paper soaked in contact cleaner, pulled a couple of times between closed contacts. 

Martin

scorron
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Thanks for the quick reply. 

I didn't have any handy way to pull vacuum, but I heated the bearings to several hundred degrees in synthetic 10w30 oil (I figured if it's good enough for my Volvo 240...), after I soaked them in acetone. I also degreased the felt and soaked in the same oil. I could rig something up to pull a vacuum, I suppose. 

I didn't go nuts on the switch contacts, but thank you, I had no idea they were platinum. Most switches I've seen of this type had a small silver pad on the contact point, not platinum. 

 

Dillen
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Wrong oil for a start. It simply doesn't have the necessary additives.

Use a good old SAE30 or a good high speed spindle oil like Mobil Velocite 6, which is what I have used for the last couple of years with great results.

 

We mustn't forget, that this is a one-phase AC-motor of the "short-circuit" type.

In theory this type of motor has no initial torque and relies solely on being extremely easy running, right from the start.

This is not just one metal object rotating inside another metal object.

This is a hard-chromed precision turned metal spindle running inside precision-cast sinter-bronze ("Oilite") bearings.

The oil sits inside pores in the bearing metal and is sucked out from the pores by a tiny vacuum created

by the rotating spindle, in turn creating an ultra-thin film of oil for it to run in.

Perfectly set up (bearings correctly oiled and aligned axially etc.) there won't be any metal-metal contact, which

again means no friction or wear to speak of.

Any oil added to the outside of the material (like oil added in drops as you would normally do) is simply being pushed away, slowly but certainly - as yours has been now, and nothing useable is coming from the pores, so you are back where you started from. - Except for the wrong oil you've added.

 

Clean off as much as you can of the oil you've added and infuse the right thing under vacuum.

Using a "Food-saver", this takes about 16-24 hours.
Using a harder vacuum, considerably less.

The motor will run as new and last for the next 30 years.

 

Martin

scorron
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I'll give the food saver a try. What about Zoom Spout turbine oil? Do you think that is the right quality? I can't find specs on it.

 

What if the bearing were treated like solid bronze? I was thinking of using a jewelers saw to cut an oil channel in the bearing, but that would be a last resort. 

 

Thanks again,

Sean

Dillen
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That'll be no and absolutely no.

Turbines typically use ball or roller bearings - completely different lubricants.
Any damage, even the slightest surface scuff inside the sinter bronze bearing, and the bearing is useless.
It's a very soft material. You can scratch it with a nail.
Don't treat sinter bronze as anything else.

Martin

Orava
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Orava replied on Fri, Sep 6 2019 9:54 AM

Dillen, have you any recomented supplier for oil? I seem that I have to buy 20liters if I buy from Finland.

 blah-blah and photographs as needed

scorron
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Thank you for the advice, Martin. I will try again on the motor bearings. 

Regarding the speed selector lever, mine was bare copper, so I glued a piece of felt to it, then oiled the felt. Is this an acceptable solution in your opinion? 

Thanks,

Sean

Dillen
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As long as it doesn't brake too much, I think it'll be fine.
I like to glue on a small sheet of teflon cut to shape.

Martin

scorron
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Thanks again for the advice.

I built a small vacuum chamber using a hand pump vacuum brake bleeder and a 1/4” brass nipple epoxied into a mason jar lid. It held -25 inches of mercury for 16 hours until bubbles stopped coming out of the bearings. I used a sewing machine/spindle oil. 

Beogram is back together and running well. I just hope it continues to do so this time. 

scorron
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I played the Beogram 3000 again last night, and according to the strobe, it is still running slow at startup (when cold) but speeding up gradually over the first 15-20 minutes. I have read that this was a problem even when the motors were brand new - is that correct? Has anybody found a solution other than motor replacement? 

The my ear, the speed is steady and consistent from one moment to the next, but over time it definitely speeds up considerably. That's a little annoying, but I guess I can live with it if, after warm up, the speed does not change. I can always adjust the speed for warm running and wait several minutes before using. 

Dillen
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Dillen replied on Tue, Sep 10 2019 1:56 PM

Wrong oil.

The motors were fine when new. Where did you read anything else?

At some point B&O issued a tech note about their stock of replacement motors getting old (decades), and that they could no longer guarantee, that the
motors would run out of the box without servicing.
That was because their replacement motors was produced at the same time as the Beograms in which they were used, and the oil in the bearings dry out regardless of use.

Martin

joeyboygolf
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SAE30 is the grade of oil used in 4 stroke lawnmower engines like Briggs and Sratton. It is available from garden maintenance or lawn mower repair establishments in quite small quantities.

Modern SAE30 could of course contain the wrong additives for the Beogram motor bearings.

Regards Graham

scorron
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Dillen:

Wrong oil.

The motors were fine when new. Where did you read anything else?

At some point B&O issued a tech note about their stock of replacement motors getting old (decades), and that they could no longer guarantee, that the
motors would run out of the box without servicing.
That was because their replacement motors was produced at the same time as the Beograms in which they were used, and the oil in the bearings dry out regardless of use.

Martin

I respectfully disagree. I started with 10w30 synthetic oil (Mobil 1, actually). At normal operating temperatures, it's characteristics should be identical to SAE30, except that it is less viscous when cold. The motor did not run well for long. I am willing to admit that the oil could have been too thick, and that I did not get enough into the bearing. 

You recommended Mobil Velocite 6 which has an ISO VG of 10 - which is significantly thinner than SAE30 - according to Mobil's website. I found a spindle oil with the same viscosity, and forced it into the bearings and felt pads by applying a medium vacuum for 12-16 hours. I still have a problem with cold start up. 

If you read the posts from "Coffee Phil" on Vinyl Engine (https://www.vinylengine.com/turntable_forum/viewtopic.php?t=101759https://www.vinylengine.com/turntable_forum/viewtopic.php?t=103680, and cetera) you'll see statements such as these:

 

"On the mid ‘70s Beograms sold in the US at least, there was an issue with the motors which no amount of cleaning would fix. The little two pole motor can develop poor temperature stability. They start out quite slow and after ~ 15 to 20 minutes come up to speed. The motors were replaced in warrantee for this reason."

"In the US (60Hz) the motors on Beogram 3000 were problematic. I have not heard of the 50 Hz versions being a problem"

"They typically work very well however the problem which you describe was chronic in the US versions of my Beogram 3000. The fix was to replace the motor."

 

Granted, these statements all come from a single person, and that source could be wrong, however, the symptoms he describes are exactly what I have experienced, and I have found at least one other mention of a US Beogram owner waiting 20 minutes before playing records because of the speed issue.

I am not new to rebuilding motors, mechanical, or electrical equipment. This is not a botched lube job. 

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