missing BG4000

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  • #1104
    hcraig244
    Beoworld Member

      Well…..here we go, first post is another episode in the continuing saga of the missing Beogram and its errant power supply….the doner machine turned upP1016717 (Copy)

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    • #3617
      hcraig244
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        So ready to be returned to its home……been quite a journey, the success is largely due to Manfys inspiration and guidance¬† regarding the voltage regulator and toroidal transformer.

        Its good to know that a failed transformer isn’t the end of the road for a BG4000

        P1016764

        #3616
        hcraig244
        Beoworld Member
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          Played over the weekend without fault………P1016760

          #1751
          hcraig244
          Beoworld Member
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            Installed the voltage regulator, bolted to the chassis, no additional heatsink required….gave her a spin and nothing is getting more than lukewarm….Martin recommends removing 2TR6 from the circuit board due to overheating causing the 6vdc supply to become unstable…..so I’m good with this, good test required and that should be that!P1016759

            #1750
            hcraig244
            Beoworld Member
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              Resistor received, however I ordered a 3w component and received a 25w instead……bit overkill but quite adequate….P1016757

              #1682
              hcraig244
              Beoworld Member
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                As I’m now down to 1 bridge rectifier I thought it would be wise to check a few things out before I do a lengthy test run:

                Output from the new 6vdc regulator = 160ma under operating load

                Output from the existing 24vdc regulator (0tr1) = 440ma under operating load

                The transformer arms are good for 1.25A so I think we’re good to go, the bridge rectifier is rated at 3.7A. I will monitor the temperatures of all components, TR1 particularly though the data sheet says its good for 80w (seems high to me).

                Also I have ordered a 33 ohm 3w resistor to see if I can drop all the heat over it instead of the regulator, I can then fasten the resistor to the chassis for cooling……

                #1679
                hcraig244
                Beoworld Member
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                  Tried a 22 ohm resistor in line with the regulator and this dropped the input voltage to a little over 10vdc…the heat dissipated by the regulator has dropped and the resistor is doing some of the work….P1016748 (Copy)

                  • This reply was modified 1 year, 6 months ago by hcraig244.
                  #1678
                  hcraig244
                  Beoworld Member
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                    This is the current wiring detail I have implemented……..revised supply

                    #1651
                    hcraig244
                    Beoworld Member
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                      this is the input to the new voltage regulator from the centre tap of the the transformer, much improved though still a little high, this measurement was taken under load, this was previously sitting at 24v

                      P1016745 (Copy)

                       

                      • This reply was modified 1 year, 6 months ago by hcraig244.
                      #1649
                      hcraig244
                      Beoworld Member
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                        moving on…..got the dual outputs from the centre tapped transformer sorted out, after a good deal of head scratching….and glasses of wine! I removed the 6vdc bridge rectifier and reinstalled the smoothing capacitor, output from the centre tap connection of the transformer to the input of the new regulator and now get a decent full wave rectification.

                        cant seem to get a jpeg loaded……..maybe later

                        • This reply was modified 1 year, 6 months ago by hcraig244.
                        #1340
                        hcraig244
                        Beoworld Member
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                          This looks like an issue with the centre tapped transformer, I have read on the internet that a common neutral on the DC outputs of dual supplies of different voltages fed from centre tapped transformers are not allowed, this may be my problem.

                          When I disconnect the 24vac supply from the transformer to the 24vdc rectifier I get the expected 12vdc from the output of the 12vdc rectifier, so I know the 12vdc rectifier is working fine..I have no problems with the 24vdc side which is working fine, as this is the required higher supply im not surprised.¬† I cant see anything untoward except the common neutral to both rectifiers……..any advice regarding this would be welcome, as always ;¬¨)

                          #1339
                          hcraig244
                          Beoworld Member
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                            Ok…..cleaned the drawing up to include the actual transformer wiring details and took some measurements…..these are all with the turntable running and under normal load conditions…everything works fine though the voltage regulator gets hot…put a heat sink on it which helps quite a bit.supply3

                            #1115
                            hcraig244
                            Beoworld Member
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                              This is how the new power supply is tied in…supply

                              #1220
                              hcraig244
                              Beoworld Member
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                                However the 6vdc fell off when the regulator went into high temp cut off……it was getting very hot!….few measurements revealed that I am getting 24v at the input to the voltage regulator instead of the 12v i was expecting, the output from the transformer is 12v to the 6v rectifier…..

                                #1117
                                hcraig244
                                Beoworld Member
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                                  This is the regulator 6vdc output under operating loadP1016727 (Copy)

                                  #1116
                                  hcraig244
                                  Beoworld Member
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                                    This is how it looks, I have the regulator connected on leads to allow measurments to be taken easilyP1016726 (Copy)

                                    #1112
                                    hcraig244
                                    Beoworld Member
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                                      timestamp is a bit of a challenge here……my replies are all jumbled up, however wired up the transformer and powered up….slowly with the variac and watched the output of the 6vdc regulator it came up nicely…..and as i wound up the variac the output started to fall back to 0vdc….like a capacitor charging up?

                                      #1111
                                      chartz
                                      BRONZE Member
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                                        Very nice and tidy Craig.

                                        #1110
                                        hcraig244
                                        Beoworld Member
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                                          This is the data sheet for the voltage regulator…Untitled

                                          #1109
                                          hcraig244
                                          Beoworld Member
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                                            just getting my head around the order of things here….I will try harder

                                            #1108
                                            hcraig244
                                            Beoworld Member
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                                              This is the data sheet for the transformer….yellow and black connected together to provide the 24v supply across orange and red to the 24vdc rectifier, connecting red and black (12v) to the 6vdc rectifier…..sounds straightforward enough 818By9byH9L._SL1500_

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