I received the tachodisc from Martin (Thanks!) and installed it in the Beogram 8000. The platter turns wonderfully and at the proper speeds. The variable speed adjustments seem to work as well. The arm moves right and left and drops and raises as it should. That's the good news.
It is still having issues. It doesn't seem to recognize the beginning of a record, or if a record is on the platter. When I press Play, the carriage moves inward, but it will continue inward until it runs out of threaded rod. It will not drop, nor will it return to rest on its own. If I press << or >> as the arm is moving, the arm will stop, then I can press Play again and the arm will drop, and track the record properly. However after 40 seconds the arm cues up and returns to its rest. When I cue the arm to the end of a record and let it run out, it will not lift and return, it just sits in the leadout groove until about 40 seconds and then cues up and returns to rest. The << and >> buttons work fine and will cue up the tonearm, and track it right and left at variable speeds depending on how hard the buttons are pushed. If I press Stop, the arm cues up and returns to its resting spot and the motor shuts off. The sensor arm bulb illuminates, but the red LED that indicates the arm is in motion doesn't light. It will blink if I press Play again while the tonearm is down. I'm not sure what the blinking LED is supposed to indicate. With the stylus on the record, when I press Pause, the arm raises, and after about 10 seconds it parks itself.
So I don't know if the problem is with the sensor arm not recognizing a record, or if the problem is in the CPU circuit that counts the revolutions of the sprial shaft. The fact that it doesn't recognize the end of the record seems to indicate a problem with the CPU not receiving the necessary information about carriage position from the revolution counter. I think I am close to getting the 8000 sorted, but I can't figure out what is causing this problem. If anyone can help me diagnose the cause of the problem, I'd appreciate it.
