This is a follow up to my recent post about the redesigned Beogram Commander remote control board, which now works in both (DC-motor) Beogr...
Wednesday, January 20, 2016
Beogram 4002 (5513): RPM Stability Test and an Updated Display on the BeoloverRPM Device
I spent some time learning to program the small display that I integrated into my BeoloverRPM device that is useful for precision RPM adjustment as well as long term RPM stability characterization. I added min and max values as well as the total measurement time. Here is an impression of the display:
Quite high res and a nice contrast! However, guys of my age at least will need reading glasses to appreciate the small font...;-). Is life ever perfect??.
Anyway, I applied this new BeoloverRPM version to the Beogram 4002 that I just got going again and I performed a 12 hour RPM measurement. Here is the resulting graph:
This is a pretty good result about matching the specified 0.05% fluctuation number of the service manual. There are four spikes that exceed this specification (they are about 0.15% deviations). I have now measured a few 4002s with DC motor, and they all seem to have these spikes once in a while if one waits long enough. I think we see here the shortcomings of purely analog feedback systems. While these spikes are clearly measurable, they will be hardly audible. Most people can only detect changes of about 0.3 to 0.7%. So this Beogram should be fine for enjoying music.