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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...

Wednesday, April 22, 2015

Beogram 4000: Cleaning of the Tone Arm Carriage Position Switches and a Non-Returning Carriage

Before doing my standard rebuilding steps on the Beogram 4000 that I am currently restoring I decided to make sure the control system works properly. Earlier tests revealed that the arm carriage would not return to the home position if set loose across the platter when no record was present. Essentially, the carriage would run all the way to the center of the record and then stop. If everything is o.k. it should trigger the End Switch (ES) and then return to the home position all the way to the right and turn the turntable off.

I decided to start tackling this issue by making sure the carriage position switches work properly. I think it is generally a good idea to give these switches some attention, since they are vital for the trouble free operation of this model. It is not too difficult to do, but I thought a video might prove helpful for other enthusiasts when they engage with this beautiful design. So, here we go:

After I was done with cleaning the switches, I tried the carriage run again. And it still did not work! Closer inspection revealed that the spring that activates the ES switch did not fully engage the switch. I removed the spring carrier a second time, and bent this particular spring a bit downwards to give the switch a bit more travel. This fixed the problem, and the carriage now returned if set loose across an empty platter.

However further play with the mechanism revealed that it was still possible to accidentally drive the carriage into an end position where the ES would not be triggered. This condition occurred when using the left-arrow on the keypad to drive the carriage beyond the point where the ES is activated (the arrow key apparently overrides the ES). In this situation the ES released again, and that prevented the carriage from returning after letting the arrow-key go.

This issue was solved by moving the spring that activates the ES a bit to the right on the carrier plate. In effect, this allows to drive the carriage to its physical end point with the arrow key, while not exceeding the turn on zone of the ES switch.

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