Hi Laurens. Here’s some things you can check. (1) Check the Belt: Ensure the belt is in good condition and properly seated. A worn or loose belt can cause speed issues. If the belt is old, consider replacing it. (2) Speed Adjustment: The Beogram 1203 has a speed adjustment mechanism. You might need to fine-tune this. Use a strobe disc to check the accuracy of the speed and adjust accordingly. (3) Clean and Lubricate the Speed Change Mechanism: Sometimes, old lubrication can cause the speed change mechanism to stick. Clean out the old lubrication and re-lubricate with a suitable oil, like sewing machine oil1. (4) Check the Motor Pulley: Make sure the motor pulley is clean and free of any debris. Sometimes, dirt or grime can affect the speed. (5) Inspect the Electronics: If the mechanical parts are all in good condition, the issue might be electronic. Check for any faulty capacitors or resistors that might need replacing. There’s also a video on Youtube about fixing a slow 1203. I gaven’t fully watched it. But maybe you find something helpful. https://youtu.be/cQpVK42wgms?feature=shared

Lubricating the motor bearings is not that easy; Clean out in acetone bath for 24 hours, slush around every now and then to flush as much dirt and dry oil remains out of the pores in the metal as possible. Allow to airdry for a few hours. Submerge in sinter oil containing the correct and required additives. Pull vacuum until bubbling stops. Release vaccum and leave bearings in the oil for a few hours to allow the oil to soak into the pores. -And if the bearings are already worn from running without proper lubrication, even for just a brief moment, they won't ever be any good again. Easier is to simply replace the bearings (read here): https://www.dksoundparts.com/product/motor-bearings-set-for-beogram-motor-with-3mm-spindle/ Martin