This post is a wrap up of the functional testing on this Beogram 8002 turntable.
For my own reference between various Beogram 8002 turntables I like to collect oscilloscope photos of key Beogram signals.
Here is a photo of my test leads connected to the main board of the Beogram 8002.
Position Sensor 1 (the position of the tangential arm assembly)
Position Sensor 2
Detector Arm (the signal from the sensor in the fixed arm)
Speed Sensor (the signal from the platter speed sensor)
Servo Motor Forward
Servo Motor Reverse
My oscilloscope has four channels so I will just monitor what is happening on the servo motor and the position sensors first.
As a reference, here are the signals when the Beogram 8002 is parked in the Standby mode.
Pressing the Play button drives the Beogram tangential arm assembly forward and disengages the SO switch.
Notice there is a designed delay from when the SO switch disengages and the position sensors start to cycle.
Once the tonearm sets down the servo will advance again as the tonearm moves through the lead-in groove of a record.
There will be periodic activity on the position sensors and servo forward voltage as a record plays and the Beogram keeps the tonearm tangential to the record. The position sensor signal pulses will vary depending on how much compensation the servo motor is told to adjust for by the tracking sensor.
When the end of the record is reached the servo motor moves the tonearm through the run-out groove and stops. The motor reverses and begins the return of the tangential arm assembly back to the Standby mode position.
The reverse to home (or Standby position) can also be initiated during record play by pressing the Stop button.
Another action that results in a return to the Standby position is when the fast scanning button is used to move the tonearm forward until the maximum forward position is reached.
To look at the platter speed sensor and the arm detector sensor I swapped out those test leads with the two oscilloscope leads I had been using to monitor the servo motor.
I will just show one photo with these connected.
That meant adding the Tracking Sensor signal probe wire to the main board.
Looking at the basic turntable functions again with the tracking sensor being monitored gives these photos.
This picture is of typical record play events over a 12 second period.
I am ready now to do some minor work on the Beogram 8002 cabinet and reassemble this turntable for the listening tests.