This is a long shot but I was wondering if anybody knew anything about the VXR S17. The shaking speed seems inconsistent when set at a certain level. If anybody had any info or manual or even a circuit diagram I would be very grateful.

Here are a couple of "drop short" answers to your "long shot" question!

1) Brushes ... as in "check"!
2) Rheostat (does it have one?) ... check ... as in dirty track (or worn in one place).
3) Or it could also be due to our old friend ... accumulated crud (fluff, carbon deposits or dust, or muck in general) ... or even lack of lubrication!

I admit that the model number you give doesn't ring any bells - but somehow I doubt that a manual is really required.

The model is unknown.

If it's a single spindle shaker, you need to replace the bushes and bearings and if it's a flat bed shaker you need to check the drive belt for stretch areas and replace if necessary.

These are general service items and depending the manufacturer, you should be able to buy these from them at relatively low cost. Most OEM's will also send you the service documentation just by sending them an e-mail. This is unless it was made in some back garage in China with the original purchase being done through alibaba.com or the like

The roller type (If this is you have) has an off-set shaft that drives up to 24 lateral arms (in most cases for smaller labs this will be 12 lateral arms, 6 to a side). This shaft gets worn over time and frankly it will cost you cheaper to replace the whole roller shaker than to buy and fit a new shaft

Thanks for you help, the motor was the first thing I looked at, but it moves quite freely when spun by hand. I will try some of the suggestions though.

Yes ... but what about the brushes (length ... are they still making good spring loaded contact)?

As Jandre has illustrated, I should have added "mechanism" (as in worn, sticking etc.) to my list of suspects.

But (also as mentioned) it really depends on the type of "shaker", which can cover a multitude of variations ... from rocking, rolling, orbital, vortex and many more ... with mechanisms from a simple spindle to a complex system of cams and levers!

So ... what do you have there?

The motor is brushless. The unit is fairly simple it seems to be a motor attached to an of centre ball baring thing with a weight on one side of the motor. The feet of the platform and the device are on springs.

Could it be my old friend, the shaded-pole motor, I wonder?

On/off ... or is there some sort of (attempt at) speed control? I'm guessing not (if it is indeed a shaded-pole type). Fast, slow (geared)?

What fun! Any more clues, symptoms or other interesting snippets of information?

Just out of interest really ... how would you describe the action ? Rotating, cyclic, orbital, rocking ... ? And what is being "shaken" ... test tubes, flasks, Petri dishes, blood bags ... ?

I tried to post a picture but I couldn't get it to work. The platform is a 40cm by 20cm platform with a rubber surface. I think they shake beakers. Does the shaded pole motor have verticle metal strips down the side? The motion is rotory but slight the effect is to well shake (between 200 and 2200 I asume rotations per min but no units are given).At the bottom of the motor there is a metal disc with semi circles cut out at regular intervals (like its wearing a frilly skirt) which rotaes inbetween an LED and photo diode.

Shaded-pole motors are easily identified by the thick copper starting winding(s) that wrap around the laminated frame. It is (of course) these that produce the electro-magnetic "shading" (the phase shift needed for starting). Yours may not be a shaded type as they only produce a low starting torque. They also always run a bit hot (even when off load) due to their inherent inefficiency.

The clues you have given about the weight, and the "speed", rather suggest a "vibrating platform". This is not used in the Dental Lab by any chance?

Anyway, what about the fault. What's it doing (or not doing)? And - more importantly - does it matter? That is, are the users complaining? Sometimes they might be using things like this at a fixed speed, and maybe it's working just fine for their purposes!