Beogram 8000: Replacing the Carriage Belt

Another loose end in the Beogram 8000 that I am readying for shipping I needed to attend to: I earlier noticed that the carriage belt was quite loose, i.e. at the end of its lifetime. On the occasion of my recent effort to replace a cracked BUNA-N volume belt in a Beomaster 6000 I ordered samples of the entire lineup of EPDM 1/16 O-rings at the O-Ring Store with the goal to be ready for future belt replacements of yet unknown diameters. So I thought I probably had the proper EPDM ring for the Beogram 8000 already in stock! And indeed: It turned out that the E70025 (1-3/16" diameter) ring made a good replacement of the original belt. Here are a couple of impressions:

This shows the original belt with rotary encoder sensor cluster removed (just pull the plastic clamp out and carefully pull the board up while making sure that the IR emitter passes through a gap in the encoder wheel), which is necessary to get the belts over the encoder wheel:

And here after installing the new belt:

It is interesting to note that my first attempt with a 1-1/16" belt did not work out. When I checked initially the carriage would move very well with it. However after attempting to play a record, it turned out that the Beogram would have trouble to move the arm to the run-in groove.

What happened was that the firmware in the microcontroller reduces the power on the carriage motor before the touch-down point to get a more precise positioning (and probably also because it just looks more elegant...;-). However this is apparently not done via encoder feedback but rather via a blind  flight power reduction without monitoring the encoder action. This resulted in a very slow movement of the arm do to the unexpected friction caused by the too-tight belt. It would take several seconds from moving swiftly near the position and then via a very slow final movement to the touch-down position. Replacing the ring with the 1-3/16 version cured this issue and now it behaves like with the original ring. All good now under the hood! Playing right now my just arrived 180g reissue of Queen's 'A Day at the Races' - those were the days!...;-)