Tight bearings in Rega RB250

[denied]

I have a SystemdekIIX-900 which I bought new about twelve years ago and i've just taken it out of storage where it's been for about 6 months.

It has a Rega RB250 arm fitted (although badged as Moth).

The arm moves freely up-and-down but has resistance side-to-side. The arm can move all the way through it's swing, doesn't bind, doesn't feel rough - it's just there is resistance. It's not like you have to push it with any noticeable force, but it certainly won't track a record groove - I tried playing a record and guess what? The arm stays still.

Any suggesions as to how I resolve this..?

Thanks.

 

[makinson1]

You must clean and re-lube all of the bearings. Sorry. No easy way out of that. Disassemble the bearings in the yoke (in a clean environment). Wear surgical gloves that do not have clay filler and talcum powder in them. I use denatured alcohol to clean them so it won't attack any of the plastic parts. My latest favorite lube for bearings is a product marketed by the people that make PB-Blaster (Sold at auto-parts stores). It is called GDL and is a Zinc-phosphate compound with a name as long as your arm. It is OK for food-service machines so I guess you could drink the stuff, but you might experience a mild laxitive effect similar to the way castor oil goes through a goose. This oil is the anti-wear additive used in most motor oils to keep your pistons from welding themselves to the cylinder walls at high RPM.

 

[denied]

Most useful. So far i've tried turning the arm upside down and letting some light machine oil sit in the pivot tube overnight in an attempt to penetrate the bearing, but with no luck.

So how do I dissassemble the bearings in order to re-lube..? Do I need to remove the bearing from the pivot tube without ruining the arm..? I've already removed the retaining nut and desoldered the wires, but the arm itself wants to stay in the bearing at the moment! I've looked for this sort of stuff on the internet without joy..

Sorry for all the questions and thanks for the help.

 

[makinson1]

Short answer: Very Carefully. I think the 250, as opposed to the 300, has pressed in bearing shells (really tiny little devils) so once you loosen up or remove the adjustment capscrews you would have to be very careful not to hurt them. You may be able to lossen everything up enough to flush the accumulated gunk out of the bearings and apply some lube to the unit. Tools: good set of jewelry drivers, needle nose pliers with really small tips (www.hosfelt.com), lots of strong light, magnifier- headband type.

 

[jeff spall]

Hi,

I've just joined this forum and this is my first post, but I have recently taken a couple of RB250's completely apart, so I might be able to offer an opinion.

On the RB250, the bearings and the brass stubs that support them are held in place with a *lot* of locktite and the chances of getting the arm apart without damaging them are very slim. The brass bearing stubs are glued so tight and the brass is so soft that you are likely to badly damage the screwdriver slot.
Once the stubs are out, you will need to drift out the bearings as they are glued pretty tight as well. Just how much loctite is used varies very much from arm to arm.

If you have bad bearings then a high-quality replacement is very readily available. An ABEC5 SKF bearing can be had from RS components (in the UK, but they do international shipping)
http://rswww.co.uk

under their part number 540-306

The basic specification is a flanged, shielded radial bearing 6mm inside diameter, 13mm outside, 1mm flanges, so you could source it anywhere.

Here's my rega arm stuff and a picture of a dismantled arm:
http://www.william-reed.net/audio/

- in "rega arm mods part 1" there's a sketch of the standard bearing setup.

regards, jeff

 

[jeff spall]

Sorry, I should have added that a common cause of tight vertical (yaw) bearings is that the nut on the bottom of the vertical shaft has been moved. Again, this is fixed with locktite as are the bearings but, if it's been disturbed by, say, holding it whist the arm yoke is put on it can tighten up. Once this nut is undone, the vertical shaft (sorry, don't know what to call these bits!) can be pressed out of the bearings if you want to.

The re-assembly procedure would be to lightly polish the shaft so that it isn't too tight a fit in the bearings (push fit rather than press), then screw the shaft onto the yoke with some locktite. Assemble the shaft into the bearings. You'll notice some bearing play as these are *not* precision parts. Then you add the nut and very carefully tighten it to get the right, tiny, bearing pre-load. Can't give you a measurement, but you reach a point with no play but free rotation.

If there's any hint of "grittiness" or binding, then I guess the bearings are shot and you will have to go back to stage one and replace them. At least you then have the satisfaction that you have used a nice precision pair as replacements.

regards, jeff

 

[Rufus.T.Firefly]

rb 300 bearings

I have the same problem with a Rega rb300 arm, which was on a turntable I bought recently. The wiring was replaced, and I think the bearing must have been damaged, because lubing did not solve the tracking problem. My question is whether you
know if the rb 300 arm uses the same bearing as the rb 250 that has been described in this thread? Help would be wonderful, I have gone clinical over this.

 

[makinson1]

You may need a new bearing. Press it out carefully with an arbor press or something like that. If you take it in hand to a bearing supply house they will be able to match it. As far as the ABEC No# go higher is better. Graham claims they use ABEC7 in thier tone arm. I once built a knock off of the Linn Ittok with some ABEC9's from the gyros in the Patriot missile.

 

[Rufus.T.Firefly]

Thanks for the advice Makinson1, I am gathering my courage and will try
to remove the bearing next weekend.

 

[Panicos K]

Inside the vertical ''tube''through which the internal wires pass,there are two tiny hollow black rubber pieces.When RB250/300 are rewired,these sometimes come out of place,and might block movement of the arm.Check if this is the case for both the 250 and 300.

 

[makinson1]

Ditto that on being careful about removing the cable assembly. I make my own cables with better wire than the Incognito retro-fit and end up using standard chem lab rubber stoppers for test tubes.