A Pair of Beomaster 1900 Receivers for Restoration: Finishing up Unit #1

The first of the two Beomaster 1900 receivers is now complete.  

I wrapped up the testing tonight by checking the Total Harmonic Distortion (THD) at 1KHz with 20 Watts of power out of the Beomaster 1900 into my dummy 8Ω speaker load as well as the Frequency Response from 20Hz to 20KHz at an output level of 20 Watts.

Here is a photo again of the dummy speaker load test setup.

The Total Harmonic Distortion (THD) with a 1Khz sine wave into the Beomaster 1900 Tape source input and maximum rated power (20 Watts) across the dummy speaker load measured 0.068% which is well below the service manual specified maximum THD level of 0.2%.

Next I performed a frequency response measurement from 20Hz to 20KHz frequencies with and input level of 260mV into the Tape input and the power level at 20 Watts again.

The result was a ±1 dB swing from the 20Hz to 20KHz frequency range. That is pretty much the same as I measured for the Beomaster 2400 receiver I restored earlier.

 

Those are very satisfactory measurements for this Bang & Olufsen series amplifier.

This Beomaster will now go into a listening room while I get the second Beomaster 1900 unit restored.

Here are a couple of final photos from the workbench.
This Beomaster 1900 receiver shouldn't be seeing the workbench again for fifty years.