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Saturday, September 16, 2017

Beogram 8000: A Tangential Arm Drive Problem

In cleaning and lubricating the Beogram mechanics one of the first things I wanted to check on is the small plastic bearing that travels the tangential arm drive screw to move the tangential arm assembly across a record and back to the rest position.

I wasn't too surprised when I discovered the bearing had a broken tab on the side that pushes the arm assembly back to stop. That seems to be a pretty common state in these Beogram 8000 units I am seeing.


In the last Beogram 8000 project I ran into this exact same issue where the round, plastic arm drive bearing (I called it a bushing in that post) had a broken tab where the mounting bracket attaches. I was able to re-attach the bracket and the Beogram was able to function. After returning the turntable to its owner the Beogram had problems with its arm lowering. I had the Beogram shipped back to me to discover that problem was due to a piece of FOD interfering with the arm lowering mechanism. That FOD piece was the broken tab off the plastic drive bearing!

I immediately looked at the arm lowering mechanism of this new Beogram 8000 turntable and sure enough, there was the broken plastic piece sitting in the compartment where the arm lowering mechanism is. This is indeed the same problem as the last Beogram 8000. Now that is a surprise.





Here is a closer look at the broken arm bearing pieces.





As I said earlier, this appears to be a common issue with these older Beogram 8000 turntables. Extra force must be being exerted on that part of the bearing when the tangential arm assembly is moving. Perhaps it starts failing as the Beogram electronics begin to fail and the arm drive system malfunctions.


Also as I mentioned, the Beogram can still function with the broken drive bearing tab. However, the drive shaft will likely make a noticeably louder sound when traveling the direction that is pushing on the broken tab. The real solution is to replace the bearing with a fully intact one. I do have some spare Beogram 8000 units but all of them except one also had arm bearings with same broken tab. I used that intact bearing on the previous Beogram 8000 project.

Now I will have to look for a new solution.





I might be able to fabricate something I can epoxy on the side of the bearing with the broken tab but a better solution would be to come up with a 3D printed replacement part.

I am going to start looking at these arm drive bearings on all of my Beogram 8002 turntables to see if any of them have this problem.












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