Thanks, Frede.
I never thought of that and never had the problem either but I haven't done that many Beogram 1000's.
I have noticed something else, though. I'm sure you and others have too.
Symptoms are that the motor will either not start at all or it will start far too slow and only
slowly gain speed. After 10-20 minutes of warming up this way the speed may be correct but
there's also a chance it won't ever reach that point.
The motor bearings are sintered bronze. The material is poreus and has been oil-filled from the factory.
The motor shaft runs inside the bearings on a thin film of oil, sucked out from the pores. When running
properly there's no metallic contact from the shaft to the bearings (and no mechanical wear to speak of).
Over the years, some of the oil is used, some evaporates, the rest dries up and becomes a fairly hard sticky mass.
It's very difficult to get the dried oil out of the bearings, several turns with heat, vacuum, isopropanol alcohol,
thinner etc. will help a bit and the same procedure is used for pressing in fresh good old SAE30 oil
but still, after this treatment many motors won't run properly.
That is, the motor may run fine when put together and tested but let it sit for a week or two and it will have
the same speed problem again. This can be very frustrating.
The reason is not easy to see with the naked eye but using a microscope you can see that the
inner surface of a good bearing has its pores intact whereas the problem bearings have their pores smeared out.
This happens when the oil is used up or has dried to a point where no oil can be sucked out from the pores
anymore, leaving the shaft and bearings running metal against metal.
The bronze material used is very soft. Bronze is a soft metal in itself and the pores make it particularly delicate.
If the pores have been smeared out the bearing has been destroyed and will never run fine again, no matter
how much oil you add.
A "healthy" bearing may be saved and run fine again for many years.
In other words; If your Beogram is still running fine, it will need service now while its bearings
are still good enough to re-oil !
The above applies to all Beogram using 1-phase AC motors; Beogram 1000, 1001, 1200, 1202, 1203, 1500, 2000,
3000 etc.
Beogram 1000 came with 4 different motors (if I remember correctly). They are built slightly different
and have different bearing sizes but the principle is the same.
Theoretically, these 1-phase AC motors of the "short-circuit" type has no initial torque so an extra startup
winding has been added. That same winding also guarantees that the motor starts up the right way every time.
This low torque makes them particularly sensitive to proper lubrication.
Martin