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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...

Sunday, November 15, 2015

Beogram 4000: Lubricating and Adjusting the Solenoid to Tonearm Linkages

After installing a working solenoid and removing the alien voltage regulator from the Beogram 4000 that I am currently restoring, I tested the arm mechanism, but it was still a bit sluggish. This  suggested that the connecting linkage between damper and tonearm lift needed lubrication. Also the horizontal parallelism of the tonearm was grossly out of whack. I tried to adjust this with the set screw in the connecting arm on the back of the tonearm counter weight, but this screw was epoxied in, preventing the insertion of a screwdriver...another result of Mr. Handyman's restoration efforts, I guess. 
This shows the back of the tonearm assembly:

First I took the connecting arm out and extracted the set screw by heating the arm with my rework hot air blower:

After removing the set screw:

While I had the arm out I also installed a nut and a washer on the screw that holds the arm counterweight to replace the locking ring that is normally installed. This allows to fix the zero-weight position in place by tightening the nut for much better long-term stability (and survivability during shipping):

After installing the arm back and adjusting the set screw properly the arm was horizontal and aligned with the sensor arm as it should:

Then I took out the sensor arm assembly to extract the solenoid to arm linkage:

I recently made a video that shows in detail how to do this procedure. The difference here was that the linkage was not completely seized to its pin, and that the sensor arm could be moved a bit forward easily after removing the screw that holds it in place:

This is important to give the linkage a bit more room when it is pushed out from its pin. There is a possibility to damage the wiring that goes into the sensor arm if this is not done. After removing the locking washer and the spring underneath (careful here...this spring can jump off if one is not aware), I lifted the linkage out

and cleaned everything. Then I added a bit of silicone grease to the pin and put everything back together. After installing and aligning the sensor arm assembly, the tone arm snapped into place as it should when rotated horizontally out of its rest position. Also, after trying out the mechanism by pressing ON revealed a smooth operation of the arm lift. This hopefully concludes the tonearm mechanism restoration.

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