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Beolover SyncDrive: DC Platter Motor Replacement for Beogram 4002 and 4004 (Type 551x and 552x)

Late Beogram 4002 and the 4004 (Types 551x and 552x), which have DC platter motors instead of the earlier synchronous AC motors usually suff...

Sunday, July 22, 2018

Beomaster 4400 (2419): No Load Current Adjustment

Here is a quick updated on the Beomaster 4400. Yesterday the Beomaster was powered up for the first time after the restoration. All of the power supply voltages checked out good. Continuing on today I set the no load current. That procedure calls for measuring across the two emitter resistors on each channel with the volume at zero and no speakers connected. The idle current trimmers are adjusted so that each channel is at 10mV to 15mV across their respective output emitters.

To start with I am setting these on the low end of the range so I set each to 10.2mV. I will test with that for a while and monitor the temperatures of the output transistors. Once I am comfortable with that I will look at increasing the output.

Here are the left and right channel adjustments.

I'm afraid I couldn't wait to hear what this amplifier sounds like so I connected up an iPod Nano to TP2 and the Beomaster speaker 1 outputs to my Beovox S-55 speakers (that I always test with in the shop).

I realize it is too early and there are still performance tests to run but the Beomaster sounds great in this first test.

I checked out the FM tuner controls. The large tuning dial and the six presets all work. Stereo decoding appears to be working fine. The signal strength looks strong but I will check everything out further in the next few days.

So far I have had power on the Beomaster for over an hour with it playing through the Beovox S-55 speakers. The heatsink fins remain cool. I will let the Beomaster continue to play for twenty-four hours.

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