After installing the new hood on the Beogram 4000 that I am finishing up I gave it some more playtime together with my Beomaster 6000 4-Channel (they just like each other...;-) and I realized that the arm lowered too fast. I first tried to increase the damper time constant by screwing the vale screw a bit further in, but to no avail. In fact the damper got very slow, but the needle still lowered very fast into the groove. What is going on!
I took the panels off again and had a close look. It turns out that the damper to tonearm linkage is very close to the damper plunger, and so it gets moved immediately when the damper starts moving. Since the damper needs to build up a bit of vacuum inside before it can do its damping action it is faster for the first mm or so and then becomes fully damped. This had the negative effect that the arm would be lowered already during this first mm before the damping action finally set in.
I always wondered why later 4002/4004 models have a modified damper to arm linkage. This shows the modern version:
The setscrew on the lower end of the linkage allows the change of the distance between damper and linkage when the arm is up. The adjustment instructions in the 4002 manual yield a situation where there is a small gap between damper plunger and linkage, so that the damper does not rush into the linkage during its first mm of movement. This causes the arm to be lowered only after the motion is fully damped.
The Beogram 4000 on the other hand (and some older 4002 versions) have a linkage that cannot be adjusted:
I scratched my head a bit how to introduce that gap a the damper plunger, and after a while it struck me that I could also alter the upper end of the linkage where it controls the lowering of the arm. I added a few layers of shrink tubing to the connecting end which lifted the linkage up a bit, creating the desired mm gap on the other end:
After this modification the arm lowered very smoothly.
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