Beogram 8000: Using the Workbench Beogram 8000 to Test a Speed Sensor Assembly

Now that the Workbench Beogram 8000 test setup has a three-pin connector in the platter drive harness for swapping speed sensor assemblies I can give that a try.

Here is the Workbench Beogram 8000 speed sensor assembly being swapped out with another assembly sent to me for testing.

The speed sensor assembly test candidate was taken out of its P4 wire harness and still has its P4 contacts. The owner should be able to re-insert them when I send back the tested speed sensor assembly.

I ended up making an adapter harness that would plug into my Workbench BG8000 3-pin test connector on one end and has mini-grabber probes on the other end.

In this case the mini-grabbers attach to the wires from the speed sensor assembly being tested.

Exercising the Beogram 8000 Play function with an empty platter I observed the Beogram search for a record while changing from 33.33 RPM to 45 RPM (as expected).  The speeds locked in easily so I think it is fair to say this speed sensor assembly is good.

I was curious as to how this other speed sensor assembly looks compared to the speed sensor that belongs to the Workbench Beogram 8000 turntable.

For that check I re-installed my Workbench BG8000 main board assembly.  That is because it is wired with probes for the sensors. I wanted to use my oscilloscope to capture a picture of the Beogram 8000 speed sensor assemblies at work and see how they compare.

My four probes for this test are -
1. Position Sensor 1

2. Position Sensor 2

3. The speed sensor LDR signal as it comes from the 1P4-7 connector

4. The speed sensor signal as it passes through the 1IC1 op-amp.

Here is a picture of the oscilloscope measurements I made.
I have one image for each sensor assembly at 33.33 RPM and 45 RPM...so a total of four pictures.
I arranged them together on one image so I can align the images to compare the speeds.

Not really surprising, the two sensor measurements do look different (because they are two different light sensitive devices).  However, even thought the signals do look different you can see that the period of the two speed sensor devices is the same (corresponding to 45 RPM and 33.33 RPM).

It is interesting that my Workbench turntable's sensor assembly operates at a 50% duty cycle while the test sensor assembly is less (maybe 35 to 40 percent ?).
That is another measurement I will start making on these Beogram 800x turntable restorations so I can compare them from turntable to turntable.

With both sensor assemblies this Beogarm 8000 was able to lock in the correct platter speed. 
I am declaring this speed sensor assembly sent for evaluation is good.