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Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Tuesday, May 11, 2021

Beogram From North Carolina: Speed Control and Braking Working Again

The speed control and braking problem described in the previous post about this Beogram 8002 is fixed now.  It turned out to be an easy repair that was made easier to diagnose since I have the luxury of owning quite a few spare, fully functional boards for the Beogram 8002.  It is one of my favorite Beogram turntables and I have several that I use for my own use. 

So instead of diving into a search for a bad sensor, my first trouble-shooting step was to swap the Beogram 8002 control boards.  This would quickly tell me if the problem was a sensor or a board problem.

It was a board problem.  The swapped board worked perfectly. 
That meant the problem was either a bad connection or a failed component on the circuit board.
Before pulling parts it is always a good idea to carefully inspect the boards first.
Sure enough...I found a wire that came loose.  Looking up the wire's function made sense why it was causing the problem I experienced.  The wire was for the Beogram platter speed control.  It doesn't get more obvious than that.

This picture shows the speed sensor wire (the red dots in the photo) fitted properly again.



























This excerpt from the Beogram 8002 schematic shows the wire function.





























For a reference, here is speed sensor 0PE2



Hooking the Beogram 8002 components back up and checking the Play test again results in the speed control and braking functions doing their job.

The Beogram 8002 speed indicator now displays the full speed values (down to two digits) that it measures during operation of the platter.

Starting with Standby mode followed by 33.33 RPM and 45.00 RPM here are some photos.























































Now I think all of the electrical functions of this Beogram 8002 are working correctly.
I will do some measurements tomorrow to verify that thinking but for now I am going to stop and enjoy the feeling of solving the problem :-).

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