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Monday, January 1, 2018

Beogram 4002 (5513): Restoration of Arm Lowering and Tracking Systems

When I start a new 4002 restoration the first step is usually to rebuild the arm lowering and tracking systems. The arm lowering mechanism usually needs attention due to hardened lubricants that impede the action of the solenoid and the damper assemblies. For this one needs to disassemble the mechanism. This shows it assembled:
and after taking the solenoid and the linkages out:
Once the parts are on the bench
one can clean them and re-lubricate everything. 

After reassembly it was time to get to the linkage that connects the damper plunger to the tone arm. This linkage frequently causes arm lowering delays, especially after a 4002 has been in storage for a while. To get to it the sensor arm assembly needs to be removed. This shows the assembly from the back:
and after extracting it:
The linkage can be removed after taking the retaining washer off (careful with that since there is a small spring underneath it that can be lost very easily):
After cleaning and re-lubricating its pivot point the arm can be replaced. And then it is time to adjust the horizontal parallelism to ensure that both arms are parallel and orthogonal to the carriage travel vector:
Once this was done I replaced the tracking sensor light source with a LED based drop-in assembly that I designed a while ago. This shows the original tracking sensor bulb housing (black square):
After unsoldering its two leads and removal of the two bolts that hold it in place it can be extracted. This picture shows it in comparison with the replacement Beolover part:

The small blue 'box' is a trimmer that allows adjustment of the light intensity of the LED. This is very help fun for fine tuning the tracking sensitivity of the system. This shows the LED assembly implanted:
Like all Beolover parts featured on this blog, this assembly is available to other B&O enthusiasts. Just send me an email or use the contact form to the right.
The final step of this part of the restoration was to replace the cracking-prone carriage pulley with a machined aluminum replacement (let me know if you are interested in getting a pulley, I'd be happy to get you in touch with Nick who is our supplier for this part). This shows the original pulley in place:
And the lovely looking aluminum part installed:
And this concludes this part of the restoration process.













1 comment:

  1. I am follow all the process with great expectation. Thank you.

    ReplyDelete

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