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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...

Monday, November 23, 2015

MMC20 Cartridge Mount Replacement: Third Design Iteration

This is a follow-up to my initial posts about the design of a MMC20 cartridge mount replacement. The first design iteration is discussed here and the second one here. The result of the second iteration was pretty close as in that I was able to stick a cartridge on it and that the base fit into the arm tube of a Beogram 400x. The issues with V2 were that the angle at which the cartridge mounted was about 4 degree off and that the cartridge was a bit loose. Furthermore, the nylon based print was too flexible. 

Version 3 shown here uses a different, stiffer material and I changed the geometry a bit to ensure proper mounting angle and a tighter cartridge fit. Here are a few impressions:

The mount now fits with a decent press fit into the arm tube (I did have to sand it slightly - a concession to the still imperfect printing tolerances at Shapeways). It also looks fairly original, although the material is a bit rough in difference to the original injection molded plastic:

The good thing is that the tab is invisible once the cartridge is mounted. Here is a picture of the fit:

Quite prefect now, I would say...After I stuck the cartridge on I measured the coil resistances while wiggling the mount a bit. It seems the contacts between mount and cartridge are now stable!
To get this ready for prime time, however, I still need to learn to gold-plate the Cu strips. Another point is to find a more perfect way for glueing the contacts PCB. Beolove springs from continuous improvement! But I am fairly positive now that this design is getting pretty close for some in-situ testing.

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Comments and suggestions are welcome!