Oster 123-02 are really loud

SOURCE: oster 76

There can also be a problem with the switch, which can be gotten to by unscrewing the the 2 screws at the end of the clipper . . .you must then test (with the thing unplugged!!!!!!!!!) to see if the switch wires are good or if the switch is broken by flipping the switch and or the toggle and then checking the wires with an ohm meter (easily available from radio shack or ?? for under 10 bucks or any kid who's into electronics. If the switch is good, when its turned on resistance goes to 0, if bad th switch shoes infinite resistance on or off . . .

If it hums and the motor is turning, but the blades don't move you need to replace the gear and or lever . . see this diagram
http://www.peasridge.co.uk/clipper-advice/clippers-products-oster-a5.shtml

SOURCE: Oster Golden A5 clippers not cutting

The stationary blades are held on by a couple of screws. Loosening these screws will allow some lateral movement of the blades. Adjust the blades till the proper alignment is restored. Just like scissors, there must be gaps between the moving and stationary blades at one point, then the moving blades close the gaps which cut the hair.

SOURCE: Bought Oster Golden A5 clippers new but did not

There is a small gun-metal colored bar at the very rear, just below the back of the blade. It pushes inward, in the direction of the blade. Push it firmly in and pull up on the teeth of the blade. It should pop upward. You can then remove the blade from the tongue that it sits upon. When you want to put it back, slide the blade back on the tongue, then, WITH THE MOTOR TURNED ON, push the blade down to its seated position. It will click into place.
Terms regarding these devices are all too often assumed as understood. For most purposes, these are what you have to know for the A5 Oster. The cover plate is the part with two screws that has the name and other info on it. If you remove the two screws and the plate, you will see a nylon part that moves the blade back and forth--that is the lever. The other end of the lever, with a hole in it, is connected to a metal part called the link. Both parts are easily removed by simply pulling them upward from the device. The bakelite gear is the part that the link sits on (the larger hole in the link). It too can be simply pulled up off the metal shaft that it rides upon (careful not to lose the washer under it). That gear is turned by the armature gear of the motor (which is where things get much too involved to cover here, but from that point on the device very rarely has problems). Incidentally, the lever, the link, and the gear can all quite simply be replaced. They are available quite inexpensively at Amazon under Oster A5 Clipper parts (note that the one speed and the two speed take different bakelite gears, but the lever and the link are the same). If you were to replace parts such as these or simply lubricate them, remember that a good white lithium grease is recommended in light application for the gear and the shafts (lever and gear shafts and armature gear). Also, the gear shaft has a hole down its middle (and two small holes that lead to the outside of the shaft. The shaft should be filled with grease so that grease can get through those small holes to lubicate the inside of the bakelite bearing. The two pads (one on each side of the lever) should be oiled. The simple way to tell if you need to replace parts is to grip the blade end of the lever while all parts are in place and try to move it back and forth, as though it were running the blade. If there is any more than the slightest movement, replace the lever (replace that anyway if the part that contacts the blade is rounded off) link and gear.
Good luck.

SOURCE: Proffesional Oster clippers model 274-69 seems to be frozen...

First, these are very sensitive to no lubrication. They should be lubricated every use to every few uses. Put a drop or two of light machine oil (sewing machine oil is about right) directly on the cutting blades. That may fix your problem. Also, watch the blades once you getit running and make sure the teeth totally pass each other or it will pull hair -- no fun! The travel of the moving blade is generally adjustable via a large plastic screw on the side of the clipper.

SOURCE: OSter Titan hair clippers

Oster titan blades. I have had mine for 5 years.
Oil one is a little ball on the side of clippers push in with oil tip. Make sure your clippers are running for this. You also have to grease them once in awhile with clipper grease. You should have a front panel that has screws. open and grease put case back on. for cord you can try an oscar fix place or try and see if the company will replace if you have not had them long. hope this helps.