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Need help understanding a power circuit (caps and diodes)



The Next CEO of Stack OverflowLM7805 and Zener DiodesPower origin and power planes placement on PCBLayout of decoupling capacitorsBulk Capacitance and Inrush Current Limiting Diodes burn for PSU first stageNeed help identifying replacement Magic Smoke ContainerNeed Help Understanding a Circuit (Atari 2600 XTAL Oscillator)Why do some capacitors not have vents?switch mode power supply diodesUnderstanding how an audio amplifying circuit worksDC Power Supply Output Caps: Electrical Advantage to using many smaller capacitors instead of few large?










8












$begingroup$


I'm trying to repair an old electric piano (Baldwin Piano Pro EP101) and I've gotten advice to check out the filter caps in the power circuit. I've metered out the voltages and I found power where I didn't expect it. Please see image:



enter image description here



Power from transformer coming in the top. Pins "I" and "J" are ground on the bottom. I've mirrored the board so the traces match up with the components on the top side.



  1. Why do I find voltage on the (-) side of the black capacitor?

  2. Why is the (+) of the black capacitor going to ground?

  3. I think both of these capacitors are in series, but why is there ground in the middle of the two caps?

  4. Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be? Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?

Am I on the right track? Should I just start pulling parts and testing them out of circuit? If you're interested in the overall problem, see the short youtube video here: Baldwin Piano Pro - Very loud noises



Edit: Thanks for the feedback.Larger picture and my attempt of a diagram. Surprised to see AC and DC volts when I measured. Not sure what that is about.





schematic





simulate this circuit – Schematic created using CircuitLab



enter image description here










share|improve this question









New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$







  • 1




    $begingroup$
    measure the voltage across the black capacitor ..... what do you get? ..... Why is the (+) of the black capacitor going to ground? because the negative terminal of the black capacitor is connected to a voltage that is more negative than ground
    $endgroup$
    – jsotola
    9 hours ago







  • 2




    $begingroup$
    I'm with @Transistor , Some details of that transformer are missing. Either those red & green transformer wires are connected somehow to the yellow transformer wires (perhaps inside the transformer), or there are other wires coming from the transformer not shown. You seem certain that I,J are ground...could there be a transformer connection to this point?
    $endgroup$
    – glen_geek
    9 hours ago










  • $begingroup$
    The overall problem looks like keyboard trouble.
    $endgroup$
    – AltAir
    9 hours ago










  • $begingroup$
    Measure Vdc across every part and Vac across the Caps. You should expect +Vdc across each cap and Vac<5%Vdc. Suspect any with 0V
    $endgroup$
    – Sunnyskyguy EE75
    9 hours ago










  • $begingroup$
    @glen_geek You're right. There is a wire coming from the transformer that I labeled as 0 V. I think I am wrong to call that Ground.
    $endgroup$
    – lopazopy
    6 hours ago















8












$begingroup$


I'm trying to repair an old electric piano (Baldwin Piano Pro EP101) and I've gotten advice to check out the filter caps in the power circuit. I've metered out the voltages and I found power where I didn't expect it. Please see image:



enter image description here



Power from transformer coming in the top. Pins "I" and "J" are ground on the bottom. I've mirrored the board so the traces match up with the components on the top side.



  1. Why do I find voltage on the (-) side of the black capacitor?

  2. Why is the (+) of the black capacitor going to ground?

  3. I think both of these capacitors are in series, but why is there ground in the middle of the two caps?

  4. Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be? Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?

Am I on the right track? Should I just start pulling parts and testing them out of circuit? If you're interested in the overall problem, see the short youtube video here: Baldwin Piano Pro - Very loud noises



Edit: Thanks for the feedback.Larger picture and my attempt of a diagram. Surprised to see AC and DC volts when I measured. Not sure what that is about.





schematic





simulate this circuit – Schematic created using CircuitLab



enter image description here










share|improve this question









New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$







  • 1




    $begingroup$
    measure the voltage across the black capacitor ..... what do you get? ..... Why is the (+) of the black capacitor going to ground? because the negative terminal of the black capacitor is connected to a voltage that is more negative than ground
    $endgroup$
    – jsotola
    9 hours ago







  • 2




    $begingroup$
    I'm with @Transistor , Some details of that transformer are missing. Either those red & green transformer wires are connected somehow to the yellow transformer wires (perhaps inside the transformer), or there are other wires coming from the transformer not shown. You seem certain that I,J are ground...could there be a transformer connection to this point?
    $endgroup$
    – glen_geek
    9 hours ago










  • $begingroup$
    The overall problem looks like keyboard trouble.
    $endgroup$
    – AltAir
    9 hours ago










  • $begingroup$
    Measure Vdc across every part and Vac across the Caps. You should expect +Vdc across each cap and Vac<5%Vdc. Suspect any with 0V
    $endgroup$
    – Sunnyskyguy EE75
    9 hours ago










  • $begingroup$
    @glen_geek You're right. There is a wire coming from the transformer that I labeled as 0 V. I think I am wrong to call that Ground.
    $endgroup$
    – lopazopy
    6 hours ago













8












8








8


2



$begingroup$


I'm trying to repair an old electric piano (Baldwin Piano Pro EP101) and I've gotten advice to check out the filter caps in the power circuit. I've metered out the voltages and I found power where I didn't expect it. Please see image:



enter image description here



Power from transformer coming in the top. Pins "I" and "J" are ground on the bottom. I've mirrored the board so the traces match up with the components on the top side.



  1. Why do I find voltage on the (-) side of the black capacitor?

  2. Why is the (+) of the black capacitor going to ground?

  3. I think both of these capacitors are in series, but why is there ground in the middle of the two caps?

  4. Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be? Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?

Am I on the right track? Should I just start pulling parts and testing them out of circuit? If you're interested in the overall problem, see the short youtube video here: Baldwin Piano Pro - Very loud noises



Edit: Thanks for the feedback.Larger picture and my attempt of a diagram. Surprised to see AC and DC volts when I measured. Not sure what that is about.





schematic





simulate this circuit – Schematic created using CircuitLab



enter image description here










share|improve this question









New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$




I'm trying to repair an old electric piano (Baldwin Piano Pro EP101) and I've gotten advice to check out the filter caps in the power circuit. I've metered out the voltages and I found power where I didn't expect it. Please see image:



enter image description here



Power from transformer coming in the top. Pins "I" and "J" are ground on the bottom. I've mirrored the board so the traces match up with the components on the top side.



  1. Why do I find voltage on the (-) side of the black capacitor?

  2. Why is the (+) of the black capacitor going to ground?

  3. I think both of these capacitors are in series, but why is there ground in the middle of the two caps?

  4. Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be? Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?

Am I on the right track? Should I just start pulling parts and testing them out of circuit? If you're interested in the overall problem, see the short youtube video here: Baldwin Piano Pro - Very loud noises



Edit: Thanks for the feedback.Larger picture and my attempt of a diagram. Surprised to see AC and DC volts when I measured. Not sure what that is about.





schematic





simulate this circuit – Schematic created using CircuitLab



enter image description here







power capacitor diodes






share|improve this question









New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.











share|improve this question









New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









share|improve this question




share|improve this question








edited 7 hours ago







lopazopy













New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.









asked 10 hours ago









lopazopylopazopy

435




435




New contributor




lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.





New contributor





lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






lopazopy is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







  • 1




    $begingroup$
    measure the voltage across the black capacitor ..... what do you get? ..... Why is the (+) of the black capacitor going to ground? because the negative terminal of the black capacitor is connected to a voltage that is more negative than ground
    $endgroup$
    – jsotola
    9 hours ago







  • 2




    $begingroup$
    I'm with @Transistor , Some details of that transformer are missing. Either those red & green transformer wires are connected somehow to the yellow transformer wires (perhaps inside the transformer), or there are other wires coming from the transformer not shown. You seem certain that I,J are ground...could there be a transformer connection to this point?
    $endgroup$
    – glen_geek
    9 hours ago










  • $begingroup$
    The overall problem looks like keyboard trouble.
    $endgroup$
    – AltAir
    9 hours ago










  • $begingroup$
    Measure Vdc across every part and Vac across the Caps. You should expect +Vdc across each cap and Vac<5%Vdc. Suspect any with 0V
    $endgroup$
    – Sunnyskyguy EE75
    9 hours ago










  • $begingroup$
    @glen_geek You're right. There is a wire coming from the transformer that I labeled as 0 V. I think I am wrong to call that Ground.
    $endgroup$
    – lopazopy
    6 hours ago












  • 1




    $begingroup$
    measure the voltage across the black capacitor ..... what do you get? ..... Why is the (+) of the black capacitor going to ground? because the negative terminal of the black capacitor is connected to a voltage that is more negative than ground
    $endgroup$
    – jsotola
    9 hours ago







  • 2




    $begingroup$
    I'm with @Transistor , Some details of that transformer are missing. Either those red & green transformer wires are connected somehow to the yellow transformer wires (perhaps inside the transformer), or there are other wires coming from the transformer not shown. You seem certain that I,J are ground...could there be a transformer connection to this point?
    $endgroup$
    – glen_geek
    9 hours ago










  • $begingroup$
    The overall problem looks like keyboard trouble.
    $endgroup$
    – AltAir
    9 hours ago










  • $begingroup$
    Measure Vdc across every part and Vac across the Caps. You should expect +Vdc across each cap and Vac<5%Vdc. Suspect any with 0V
    $endgroup$
    – Sunnyskyguy EE75
    9 hours ago










  • $begingroup$
    @glen_geek You're right. There is a wire coming from the transformer that I labeled as 0 V. I think I am wrong to call that Ground.
    $endgroup$
    – lopazopy
    6 hours ago







1




1




$begingroup$
measure the voltage across the black capacitor ..... what do you get? ..... Why is the (+) of the black capacitor going to ground? because the negative terminal of the black capacitor is connected to a voltage that is more negative than ground
$endgroup$
– jsotola
9 hours ago





$begingroup$
measure the voltage across the black capacitor ..... what do you get? ..... Why is the (+) of the black capacitor going to ground? because the negative terminal of the black capacitor is connected to a voltage that is more negative than ground
$endgroup$
– jsotola
9 hours ago





2




2




$begingroup$
I'm with @Transistor , Some details of that transformer are missing. Either those red & green transformer wires are connected somehow to the yellow transformer wires (perhaps inside the transformer), or there are other wires coming from the transformer not shown. You seem certain that I,J are ground...could there be a transformer connection to this point?
$endgroup$
– glen_geek
9 hours ago




$begingroup$
I'm with @Transistor , Some details of that transformer are missing. Either those red & green transformer wires are connected somehow to the yellow transformer wires (perhaps inside the transformer), or there are other wires coming from the transformer not shown. You seem certain that I,J are ground...could there be a transformer connection to this point?
$endgroup$
– glen_geek
9 hours ago












$begingroup$
The overall problem looks like keyboard trouble.
$endgroup$
– AltAir
9 hours ago




$begingroup$
The overall problem looks like keyboard trouble.
$endgroup$
– AltAir
9 hours ago












$begingroup$
Measure Vdc across every part and Vac across the Caps. You should expect +Vdc across each cap and Vac<5%Vdc. Suspect any with 0V
$endgroup$
– Sunnyskyguy EE75
9 hours ago




$begingroup$
Measure Vdc across every part and Vac across the Caps. You should expect +Vdc across each cap and Vac<5%Vdc. Suspect any with 0V
$endgroup$
– Sunnyskyguy EE75
9 hours ago












$begingroup$
@glen_geek You're right. There is a wire coming from the transformer that I labeled as 0 V. I think I am wrong to call that Ground.
$endgroup$
– lopazopy
6 hours ago




$begingroup$
@glen_geek You're right. There is a wire coming from the transformer that I labeled as 0 V. I think I am wrong to call that Ground.
$endgroup$
– lopazopy
6 hours ago










2 Answers
2






active

oldest

votes


















1












$begingroup$

I can only guess what those clever Japanese designers had in mind with these diodes.



Large E-caps must have a Dissipation Factor of << 1% where DF=ESR/Xc(120Hz) with 120Hz ripple current thus with the same current means Vac/Vdc =DF= <1%



Thus C1 is bad , C2 seems OK C3,C4,C5 are all bad.



I would replace all 5 Caps and consider replacing any other E-caps found on other circuit boards from Digikey or Mouser. Consult with tech support for equivalent or better in similar sizes.



enter image description here





schematic





simulate this circuit – Schematic created using CircuitLab






share|improve this answer











$endgroup$




















    7












    $begingroup$

    +1 for mirroring the underside of the board. Best practice is to draw the schematic and mark up the measured voltages. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. I suspect that there's a transformer centre-tap connected somewhere other than the top of the board so try to draw that too.




    Why do I find voltage on the (-) side of the black capacitor?




    The circuits must require both positive and negative supplies with respect to ground. This is common in audio circuits.




    Why is the (+) of the black capacitor going to ground?




    So that correct polarity is maintained.




    I think both of these capacitors are in series, but why is there ground in the middle of the two caps?




    Time for a schematic.





    schematic





    simulate this circuit – Schematic created using CircuitLab



    Figure 1. (a) A single-rail supply. (b) A split-rail supply giving both positive and voltage power outputs.




    Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be?
    Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?




    No. All is well in that regard.



    Post a schematic as best you can and we'll update the answer.






    share|improve this answer









    $endgroup$












    • $begingroup$
      Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
      $endgroup$
      – Sunnyskyguy EE75
      9 hours ago






    • 1




      $begingroup$
      My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
      $endgroup$
      – Transistor
      8 hours ago











    Your Answer





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    2 Answers
    2






    active

    oldest

    votes








    2 Answers
    2






    active

    oldest

    votes









    active

    oldest

    votes






    active

    oldest

    votes









    1












    $begingroup$

    I can only guess what those clever Japanese designers had in mind with these diodes.



    Large E-caps must have a Dissipation Factor of << 1% where DF=ESR/Xc(120Hz) with 120Hz ripple current thus with the same current means Vac/Vdc =DF= <1%



    Thus C1 is bad , C2 seems OK C3,C4,C5 are all bad.



    I would replace all 5 Caps and consider replacing any other E-caps found on other circuit boards from Digikey or Mouser. Consult with tech support for equivalent or better in similar sizes.



    enter image description here





    schematic





    simulate this circuit – Schematic created using CircuitLab






    share|improve this answer











    $endgroup$

















      1












      $begingroup$

      I can only guess what those clever Japanese designers had in mind with these diodes.



      Large E-caps must have a Dissipation Factor of << 1% where DF=ESR/Xc(120Hz) with 120Hz ripple current thus with the same current means Vac/Vdc =DF= <1%



      Thus C1 is bad , C2 seems OK C3,C4,C5 are all bad.



      I would replace all 5 Caps and consider replacing any other E-caps found on other circuit boards from Digikey or Mouser. Consult with tech support for equivalent or better in similar sizes.



      enter image description here





      schematic





      simulate this circuit – Schematic created using CircuitLab






      share|improve this answer











      $endgroup$















        1












        1








        1





        $begingroup$

        I can only guess what those clever Japanese designers had in mind with these diodes.



        Large E-caps must have a Dissipation Factor of << 1% where DF=ESR/Xc(120Hz) with 120Hz ripple current thus with the same current means Vac/Vdc =DF= <1%



        Thus C1 is bad , C2 seems OK C3,C4,C5 are all bad.



        I would replace all 5 Caps and consider replacing any other E-caps found on other circuit boards from Digikey or Mouser. Consult with tech support for equivalent or better in similar sizes.



        enter image description here





        schematic





        simulate this circuit – Schematic created using CircuitLab






        share|improve this answer











        $endgroup$



        I can only guess what those clever Japanese designers had in mind with these diodes.



        Large E-caps must have a Dissipation Factor of << 1% where DF=ESR/Xc(120Hz) with 120Hz ripple current thus with the same current means Vac/Vdc =DF= <1%



        Thus C1 is bad , C2 seems OK C3,C4,C5 are all bad.



        I would replace all 5 Caps and consider replacing any other E-caps found on other circuit boards from Digikey or Mouser. Consult with tech support for equivalent or better in similar sizes.



        enter image description here





        schematic





        simulate this circuit – Schematic created using CircuitLab







        share|improve this answer














        share|improve this answer



        share|improve this answer








        edited 3 hours ago

























        answered 3 hours ago









        Sunnyskyguy EE75Sunnyskyguy EE75

        69.9k225101




        69.9k225101























            7












            $begingroup$

            +1 for mirroring the underside of the board. Best practice is to draw the schematic and mark up the measured voltages. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. I suspect that there's a transformer centre-tap connected somewhere other than the top of the board so try to draw that too.




            Why do I find voltage on the (-) side of the black capacitor?




            The circuits must require both positive and negative supplies with respect to ground. This is common in audio circuits.




            Why is the (+) of the black capacitor going to ground?




            So that correct polarity is maintained.




            I think both of these capacitors are in series, but why is there ground in the middle of the two caps?




            Time for a schematic.





            schematic





            simulate this circuit – Schematic created using CircuitLab



            Figure 1. (a) A single-rail supply. (b) A split-rail supply giving both positive and voltage power outputs.




            Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be?
            Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?




            No. All is well in that regard.



            Post a schematic as best you can and we'll update the answer.






            share|improve this answer









            $endgroup$












            • $begingroup$
              Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
              $endgroup$
              – Sunnyskyguy EE75
              9 hours ago






            • 1




              $begingroup$
              My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
              $endgroup$
              – Transistor
              8 hours ago















            7












            $begingroup$

            +1 for mirroring the underside of the board. Best practice is to draw the schematic and mark up the measured voltages. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. I suspect that there's a transformer centre-tap connected somewhere other than the top of the board so try to draw that too.




            Why do I find voltage on the (-) side of the black capacitor?




            The circuits must require both positive and negative supplies with respect to ground. This is common in audio circuits.




            Why is the (+) of the black capacitor going to ground?




            So that correct polarity is maintained.




            I think both of these capacitors are in series, but why is there ground in the middle of the two caps?




            Time for a schematic.





            schematic





            simulate this circuit – Schematic created using CircuitLab



            Figure 1. (a) A single-rail supply. (b) A split-rail supply giving both positive and voltage power outputs.




            Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be?
            Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?




            No. All is well in that regard.



            Post a schematic as best you can and we'll update the answer.






            share|improve this answer









            $endgroup$












            • $begingroup$
              Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
              $endgroup$
              – Sunnyskyguy EE75
              9 hours ago






            • 1




              $begingroup$
              My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
              $endgroup$
              – Transistor
              8 hours ago













            7












            7








            7





            $begingroup$

            +1 for mirroring the underside of the board. Best practice is to draw the schematic and mark up the measured voltages. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. I suspect that there's a transformer centre-tap connected somewhere other than the top of the board so try to draw that too.




            Why do I find voltage on the (-) side of the black capacitor?




            The circuits must require both positive and negative supplies with respect to ground. This is common in audio circuits.




            Why is the (+) of the black capacitor going to ground?




            So that correct polarity is maintained.




            I think both of these capacitors are in series, but why is there ground in the middle of the two caps?




            Time for a schematic.





            schematic





            simulate this circuit – Schematic created using CircuitLab



            Figure 1. (a) A single-rail supply. (b) A split-rail supply giving both positive and voltage power outputs.




            Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be?
            Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?




            No. All is well in that regard.



            Post a schematic as best you can and we'll update the answer.






            share|improve this answer









            $endgroup$



            +1 for mirroring the underside of the board. Best practice is to draw the schematic and mark up the measured voltages. You can add one in using the CircuitLab button on the editor toolbar. Double-click a component to edit its properties. 'R' = rotate, 'H' = horizontal flip. 'V' = vertical flip. I suspect that there's a transformer centre-tap connected somewhere other than the top of the board so try to draw that too.




            Why do I find voltage on the (-) side of the black capacitor?




            The circuits must require both positive and negative supplies with respect to ground. This is common in audio circuits.




            Why is the (+) of the black capacitor going to ground?




            So that correct polarity is maintained.




            I think both of these capacitors are in series, but why is there ground in the middle of the two caps?




            Time for a schematic.





            schematic





            simulate this circuit – Schematic created using CircuitLab



            Figure 1. (a) A single-rail supply. (b) A split-rail supply giving both positive and voltage power outputs.




            Does it mean I have power coming in through the "M" pin at that bottom that shouldn't be?
            Or maybe one of the diodes at D9 and D10 (2nd and 3rd from the left) are bad and letting the power go the wrong way?




            No. All is well in that regard.



            Post a schematic as best you can and we'll update the answer.







            share|improve this answer












            share|improve this answer



            share|improve this answer










            answered 9 hours ago









            TransistorTransistor

            87.9k785189




            87.9k785189











            • $begingroup$
              Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
              $endgroup$
              – Sunnyskyguy EE75
              9 hours ago






            • 1




              $begingroup$
              My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
              $endgroup$
              – Transistor
              8 hours ago
















            • $begingroup$
              Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
              $endgroup$
              – Sunnyskyguy EE75
              9 hours ago






            • 1




              $begingroup$
              My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
              $endgroup$
              – Transistor
              8 hours ago















            $begingroup$
            Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
            $endgroup$
            – Sunnyskyguy EE75
            9 hours ago




            $begingroup$
            Sorry but your schematic here looks nothing like the board as all inputs go only to Anodes while an AC bridge input connects to one Anode and one Cathode on each input. But the caps are correct and there is no obvious 0V reference except may I,J which are paired.
            $endgroup$
            – Sunnyskyguy EE75
            9 hours ago




            1




            1




            $begingroup$
            My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
            $endgroup$
            – Transistor
            8 hours ago




            $begingroup$
            My Figure 1 isn't meant to be a board schematic. All the inputs go to anodes only. That's why I requested more details.
            $endgroup$
            – Transistor
            8 hours ago










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