UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier.

DMcMahon · 27th Oct 2021, 7:42 pm

The mains transformer is an RS filament transformer, so its original intended purpose was to power the heaters (filaments) of valves that require 6.3V, as Laurence has previously explained this transformer has 2 separate 6.3V secondary windings and it looks like they are wired in series to provide a nominal 12.6V output.

Transformers depending upon their design can increase voltage (step up), decrease voltage (step down) or keep the input and output voltages the same like a 1:1 isolation transformer. In this case it is a step down transformer.

The AC output from the Mains transformer goes to the bridge rectifier (which effectively is 4 rectifier diodes connected in bridge rectifier configuration encapsulated in the black module). This rectifies the AC voltage to produce a DC voltage, but it is not a clean DC, it has an AC component called ripple.

To remove/reduce the AC voltage ripple, the output of the Bridge Rectifier has to be filtered/smoothed by the Choke and the large grey reservoir electrolytic capacitor.

There may also be further filtering/de-coupling capacitors at the amplifier PCB to further clean up the DC supply.

David

27th Oct 2021, 7:42 pm	#89
DMcMahon Dekatron Join Date: Apr 2019 Location: Worthing, West Sussex, UK. Posts: 6,603	Re: Homebrew Record Player. BSR UA6 deck and RS Components. Stereo Amplifier. The mains transformer is an RS filament transformer, so its original intended purpose was to power the heaters (filaments) of valves that require 6.3V, as Laurence has previously explained this transformer has 2 separate 6.3V secondary windings and it looks like they are wired in series to provide a nominal 12.6V output. Transformers depending upon their design can increase voltage (step up), decrease voltage (step down) or keep the input and output voltages the same like a 1:1 isolation transformer. In this case it is a step down transformer. The AC output from the Mains transformer goes to the bridge rectifier (which effectively is 4 rectifier diodes connected in bridge rectifier configuration encapsulated in the black module). This rectifies the AC voltage to produce a DC voltage, but it is not a clean DC, it has an AC component called ripple. To remove/reduce the AC voltage ripple, the output of the Bridge Rectifier has to be filtered/smoothed by the Choke and the large grey reservoir electrolytic capacitor. There may also be further filtering/de-coupling capacitors at the amplifier PCB to further clean up the DC supply. David