Does golden a5 2 speed and turbo a5 2speed have same bakelite gear of 20 heads?

It sounds like you know pretty well what you're doing and mainly just need parts then. I suggest clipperparts.com. They are the kings of clipper parts and very knowledgeable if you need a little extra help

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 (if they are worn, they should be replaced. They, and the Bakelite gear, are available from various dealers through Amazon under Oster Parts). 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). Check it for worn or missing teeth.
If you don’t have a tube of oster grease, 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 small pads on each side of the lever (in the case) are oiled, not greased.
The bearings for the Oster are sleeve bearings that require oil (the one closest to the blade is served by the oil port; the little round chrome looking thing with the spring loaded ball in it). The other end is more difficult and would require disassembly, at which time it probably should be replaced.
Oster clippers, by the way, are known for getting pretty warm. Oster blade wash will help with that, as well as oiling the blades.
Hope this helps you.

bushens inside, i can replace

If the nylon lever (the tab that moves the blade back and forth) is not moving with the blade off, or only moving sometimes, chances are that you have a stripped bakelite gear. Take the two screws out of the cover plate and remove it. Remove the lever (the nylon part that moves the blade) Remove the link (the metal part that the lever connects with). Remove the bakelite gear (the part that the link fits down over). You should then be able to see if the teeth are chewed or worn off to the point that the armature gear will not turn the bakelite gear. If that is the case, replace the gear. Amazon carries both single speed and 2 speed gears under Oster A5 clipper parts. All these parts should have a light coat, where they move, of lithium grease, and the two pads (one on each side of the lever) should be oiled. You might also check the condition of your brushes (under the caps on each side of the clipper. Take cap off, remove cover from brush, remove spring and brush to see how worn they are).
Good luck.

The flange on the front bearing should face away from the fan blade (and protrude slightly up through the hole in the case toward the bakelite gear area), and the flange on the back bearing should face away from the windings (toward the switch area of the case). The felt pads around the bearing should be thoroughly soaked in oil before you put them back in, although the blade end bearing is oiled through the small oil port (the small chrome circular port near the air slots).

If the power lever (the tab that moves the blade back and forth) is not moving with the blade off, or only moving sometimes, chances are that you have a stripped bakelite gear. Take the two screws out of the cover plate and remove it. Remove the lever (the nylon part that moves the blade) Remove the link (the metal part that the lever connects with). Remove the bakelite gear (the part that the link fits down over). You should then be able to see if the teeth are chewed or worn off to the point that the armature gear will not turn the bakelite gear. If that is the case, replace the gear. Amazon carries both single speed and 2 speed gears under Oster A5 clipper parts. All these parts should have a light coat, where they move, of lithium grease, and the two pads (one on each side of the lever) should be oiled. You might also check the condition of your brushes (under the caps on each side of the clipper. Take cap off, remove cover from brush, remove spring and brush to see how worn they are).
Good luck.

If the blade mover is going when you turn the clipper on than all you need to do is take the blades apart and clean them well with a Oster spray and then oil them. I would recommend cool lube.

If the power lever (the tab that moves the blade back and forth) is not moving with the blade off, chances are that you have a stripped bakelite gear. Take the two screws out of the cover plate and remove it. Remove the lever. Remove the link (the metal part that the lever connects with). Remove the bakelite gear (the part that the link fits down over). You should then be able to see if the teeth are chewed or worn off to the point that the armature gear will not turn the bakelite gear. If that is the case, replace the gear. Amazon carries both single speed and 2 speed gears under Oster A5 clipper parts.
Good luck.

Your armature feed threads are most likely worn. This will continue to wear gears out unless the armature is replaced. Any Oster factory service center such as ourselves should be able to help. John, Shavers World. 313-534-0736

If the power lever (the tab that moves the blade back and forth) is not moving with the blade off, chances are that you have a stripped bakelite gear. Take the two screws out of the cover plate and remove it. Remove the lever. Remove the link (the metal part that the lever connects with). Remove the bakelite gear (the part that the link fits down over). You should then be able to see if the teeth are chewed or worn off to the point that the armature gear will not turn the bakelite gear. If that is the case, replace the gear. Amazon carries both single speed and 2 speed gears under Oster A5 clipper parts.
Good luck.