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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, January 20, 2019

Beogram 4004 (5526): A New DIN Plug, Final Adjustments and a Test Drive with Bob James!

After restoring the electronics and the motor of the Beogram 4004 (5526) that I am restoring right now, it was finally time to make some final adjustments, clean the aluminum surfaces, add a new DIN plug and then enjoy a first vinyl on it. Before making the adjustments, I added a M3 nut to the counterweight screw to enhance the stability of the weight calibration. This shows the original setup with a circle and some paint to hold things in place:
I added the M3 nut and a washer
and balanced the arm for zero weight.
Then I adjusted the tracking weight with a digital scale:
Then I adjusted the platter height and then the arm lowering limit that the needle misses the lower areas of the ribs (located at the set down points) by about a mm:
This is an important adjustment to ensure that the needle does not hit the ribs should it ever be lowered onto the empty platter due to a malfunction in the record detection circuit.
Then I adjusted the floating chassis to ensure a flush alignment between platter and surrounding aluminum panels. 

The final adjustment was the tracking feedback. The final fine tuning was done with the brightness adjustment trimmer on the LED light source for the sensor:

The last thing to do was to update the corroded DIN plug:
The Beogram 4004 came with a convertible DIN7 plug with the two 'additional' prongs removable that it could be turned into a DIN5 when used with non-B&O equipment. Pins 6 and 7 on the DIN7 carry the Beolink signal. This allowed using the remote control of a Beomaster 2400 to start and stop the connected 4004. 

Unfortunately, these convertible DIN7 male plugs are not available anymore. I usually install a female DIN7, which allows preserving the original DIN7 functionality, while allowing the easy conversion to DIN5 and RCA with a suitable adapter cable. 
This shows the DIN7 installed:
and connected to a DIN5 male-to-male jumper, which allowed me connecting the 4004 to my Beomaster 6000 4-Ch for testing.

I selected a just acquired vinyl record by Bob James: Lucky Seven: This album was recorded in 1979 and it has a few very nice smooth jazz funk tracks on it, most notably (IMO...;-) "Blue Lick" on the A side. Of course, I cleaned it ultrasonically with a CleanerVinyl Easy6 setup after I received the vinyl from a Discogs seller.

This shows the 4004 in action together with Bob:

Beautiful! And so far it is performing perfectly. The new 1985 motor runs very stable and it is very quiet.

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