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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, November 4, 2015

Beogram 8000: Repair of Broken Off Plastic Tabs on Tonearm Carriage with a 3D Printed Part (I)

I finally got back to the Beogram 8000 that recently arrived from Japan. After fixing the spindle rotary encoder issue, I had to put this project on hold to complete a Beomaster 8000. One of the remaining major restoration tasks was the repair of the broken off plastic tabs that hold the arm carriage to the metal rods on which it rides. They must have broken off during a rough transport experience or a similar stressful moment. Anyway, there was not much choice other than replacing the carriage with one from a donor 8000 or going creative on this issue with a 3D printer. I chose the latter since I usually cannot accept Beograms being parted out.

This picture shows the broken off tab in the back of the carriage:

and the photo below shows the other broken off tab in the front of the carriage. The white stuff is evidence that someone tried to glue the broken off part back into place, but it must have come off again:
The repair of this one will be the topic of my next post. Here is a picture of the second tab in the back that was still in immaculate condition:
It was immediately clear what was missing from the broken off tab: The part that swings underneath the rail rod on which the carriage travels. This keeps the carriage on track even if gravitational forces are briefly suspended during transport etc...

Gluing the broken off parts is futile in such cases. There is no plastic glue that can be strong enough to fix this type of issue. There is just too much torque on the part, while the contact surfaces are really skimpy and no match for the acting forces. So I set out to design a creative solution based on a 3D printed part. This is what I came up with:

The small tab clamps into the gap below the tone arm counter weight and holds the part in place. The bent section of the part goes underneath the rail holding the carriage in place. Here are two pictures of the part installed:

The part clips into place with a solid click and pretty much holds itself in place without the need of glue etc...I will nonetheless glue it once I am confident that it does its job well, to make sure that the Beogram survives its return journey to Japan. It is a pretty interesting process to design such a custom part since it needs to fit an already existing part precisely. This required a number of trial and error iterations until a satisfactory fit and a happy 'click' were achieved. Here is a picture of all the iterations that I printed before I had the one that is shown installed above:
If you look real close, every one is different. A lot of effort, but now the carriage of this Beogram is again held in place safely! At least in the back, the repair of the broken tab in the front will be the topic of my next post.

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