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By popular request (really, I got quite a few emails about this!...;-), I finally completed my Beogram DC motor restoration video! It demon...

Wednesday, September 7, 2016

Beogram 4002 (5501): Restoration of the Arm Lowering Mechanism and Installation of a New Tracking Sensor Light Source

I started the restoration of this (exciting) early 5501 type Beogram 4002 that came from the UK to my bench with the rebuilding of the arm lowering mechanism. The first step of this procedure is to remove the solenoid linkages and the damper for inspection/cleaning and re-lubrication. This shows the assembled mechanism:
This shows the disassembled and cleaned components:

The next step is to do the same for the damper-to-arm linkage. In order to get to its pivot point that needs new lubricants, one has to take out the sensor arm:
This shows the arm sideways on a piece of cloth. Removal of the retaining washer and the small spring that is underneath (careful here, if you do that at home...this spring is important but quickly lost) allows the removal of the linkage:

After the linkage is reinstalled, the arm ends to be re-implanted. At this point it is important to get the lateral parallelism properly adjusted:
The arms need to be parallel and perpendicular to the rods on which the carriage travels.
After that the vertical parallelism can be adjusted with a set screw in the back of the arm assembly:
The arms need to be at the same height (I apologize for the slightly unfocused picture taken in the 'heat of battle'...;-).

The final step is to install a new tracking sensor light source. The old lightbulbs are pretty fragile at this point in time, and so the installation of an LED based replacement is recommended to ensure day-to-day use reliability.
This shows the original light source with its black light shield:
I used a SMD LED based replacement part that I designed a while ago. It represents an improvement, not only in longevity, but also in function since it has a Beogram 4000 inspired trimmer that allows adjusting the light intensity. This is very convenient when it comes to the fine tuning of the tracking sensor feedback. I will do this procedure at a later point in time, since a few other things need to be sorted out with this lovely Beogram before I can adjust the tracking mechanism. Here is an impression of the new part installed:
The next steps will be fixing the cracked pulley and the broken end groove detection sensor, and to get the carriage position switches back into spec. 

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