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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

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

Friday, October 2, 2015

Beogram 4002 (5513): Replacing the Tracking Sensor Light Bulb with a Plug-In Ready SMD LED Assembly

Yesterday, I installed my latest version of the SMD LED light source for the tracking sensor of the Beogram 4002 (5513) that I am currently restoring.

A while ago I developed a drop-in ready SMD LED based assembly for replacing the incandescent bulb fixture. While this worked great, it still required the application of the inconvenient original tracking sensor sensitivity adjustment process. The mechanical positioning of the light sensors relative to the light source is quite tricky, and it is always chore to get this adjustment precisely right. The reason for this is that the mechanism is quite sensitive, while the adjustment mechanism is pretty coarse, requiring a lot of trial and error to get the adjustment right.

A recent beolove-affair with a Beogram 4000 taught me a better way to get this adjustment right: Add a trimmer potentiometer to the LED circuit, which allows the adjustment of the intensity of the LED. This gives an additional adjustment parameter that enables a straight forward fine tuning of the tracking response. I liked this a lot in the 4000, so I adapted the approach to the 4002's higher bulb voltage.

I made a short video about the installation and the tracking response adjustment process for this new design:

Here are a couple high-res pictures of the new LED assembly. I will be happy to provide this part to other enthusiasts!. This shows the added trimmer:

And this is a shot of the bottom side. The LED is in the same spot as the filament of the original light bulb assembly. The body of the replacement part is 3D printed and has the same shape as the lower part of the original fixture. This ensures a precise fit onto the light sensor assembly below the aperture:

This shows the part installed:

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