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Wednesday, June 14, 2017

Beogram 8000: Tracking and Tracking Force Adjustments

I am anxious to try this Beogram out playing records again. That time is almost here and tonight I took the next steps to get there.

First up is calibrating the tonearm tracking force. Most of the MMC cartridges have a recommended tracking force of 1.0 gram or a little higher. I like to calibrate the tonearm tracking force so the tracking force sliding scale is right on when the indicator is on the "1" position.

For these tracking adjustment procedures I use one of my old MMC-4000 cartridges. I fit it to the tonearm and checked the initial tracking force weight with the scale at the "1" position. It measured low.






















The adjustments for the tonearm tracking force are made by calibrating the tonearm counter-weight with the tracking force sliding scale.






















Here is the tracking force adjusted to within 0.01 grams.























I should mention that for these adjustments I want most of the Beogram functionality operating but I don't want the platter turning. Bang & Olufsen designed these turntables so you can disable the platter motor by itself. With the turntable power unplugged I pull off the P4 connector from the main board. I can now plug the turntable in and operate all of the other functions.






















This is a good time to adjust the tonearm set down position. I set this one just before the middle of the record's lead-in section.
























Now for the record tracking check. In this test the service manual instructs that the tonearm is lowered onto a record for playing while the platter is disconnected. The platter is then manually rotated and observed how many rotations of the record occur before the tangential arm motor advances the arm assembly.




























Any necessary adjustments will involve using the small screw shown above to adjust the aperture of the tracking sensor light. That adjustment will speed up or delay when the control circuit advances the arm.  I check the arm tracking at several positions.






















Now that the adjustments are done I reconnected connector P4 and gave the turntable a quick play test (without connecting the turntable to any amplifier). This is just to get a good feeling that it is ready to bundle up the Beogram case and give the turntable a real functional test.






















That step will have to wait until tomorrow.

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