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  1. I don't think they made transformers, but they...

    I don't think they made transformers, but they received transformers from one of their suppliers. I.m pretty sure no one supplier ship to Marshall transformers like that but pretty much well packed...
  2. Those screen draw (sometimes) current at...

    Those screen draw (sometimes) current at startup...a lot, why ?
    I asked just to share opinions about possible scenarios by the other techs experience as for me no one power tubes I used till now...
  3. ..and Yes, it was confirmed. It is a bad tube. I...

    ..and Yes, it was confirmed. It is a bad tube. I swapped it to the other side of the rail. After some successful starts up yesterday, today it was time to smoke its 1k/ 5w screen grid resistor into...
  4. ....like this ? :)...

    ....like this ? :)
    https://m.youtube.com/watch?v=_2raNqztPX0
  5. Thanks, I will swap it on other position and...

    Thanks, I will swap it on other position and hope to confirm the tube is bad.
  6. Most probable reason for screen resistor burning

    Hello,
    I recorded a issue to one of my power tube from a new 6CA7 matched set. At start up one of the screen resistor it start to burn. It is happen just at first startup after the amp stayed off...
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    It is something which intrigues in Rod Elliot...

    It is something which intrigues in Rod Elliot floating paraphase description , as: "The second form is shown shown below (version 2), and it works by using the second valve as a unity gain inverter,...
  8. The "wattage" is expression of power and is...

    The "wattage" is expression of power and is related by the heat dissipated by the speaker coil in You instance. You have to determine this as maximum admissible condition. Maybe some guys know how...
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    That is correct

    That is correct
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    Sure, I.ll need to do the amplification of...

    Sure, I.ll need to do the amplification of paraphase more than unity by a factor. That meant less local feedback. In consequence the feedback resistor should be bigger, That is correct ? I used 470k...
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    Can be introduced in simulation a build-out...

    Can be introduced in simulation a build-out resistor to balance the output impedance as M Blencowe suggested, please?
    ...
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    It,s a "splitted" PT secondary, as well can run...

    It,s a "splitted" PT secondary, as well can run the amp in class B operation with max voltage the tubes can handle( think 800V to EL34) but keeping screens to a safe 400V. See old sixties Dynacords...
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    double post , sorry

    double post , sorry
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    Latest news. Before leaving the house I still...

    Latest news.
    Before leaving the house I still found some time to modify the bias circuit as in picture below, as it was suggested:

    55139

    Now the amp is absolutely quiet. Zero noise, none.
    I...
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    Thanks for You good intentions but in two hours...

    Thanks for You good intentions but in two hours have to go at work, I.m very sorry must I leave You. Thanks for support gents. Have a nice week!
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    It is not, take a look at the pics in post 95

    It is not, take a look at the pics in post 95
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    No , there is one cap which goes to second triode...

    No , there is one cap which goes to second triode grid, This was changed. The couplings to power stage are the same 47nf
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    I posted wrong pics from rush, Now there are the...

    I posted wrong pics from rush, Now there are the right one , Sorry.
    I just changed the capacitor between first and second triode 47nf and 470 nf. Didn't see any changes
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    470n 55137 47nf 55138 This was picked...

    470n

    55137

    47nf

    55138

    This was picked up with ground clips to chassis. Previous was with ground clips floated, and also I used a digital filter to smooth the traces.
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    No, this was done with ground clips floated,...

    No, this was done with ground clips floated, seems it is not right. Post other pics in minute
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    The source of noise is the ripple from bias...

    The source of noise is the ripple from bias supply as it was confirmed. The problem is why is not cancelled in power stage. Is not a subject of any ground loops as it is very simple, but I.ll check...
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    Ok, I tied the inverter back to power grids and...

    Ok, I tied the inverter back to power grids and this is what I get in differential mode:

    This is with 47nF interstage

    55131

    This is with 470nF interstage

    55132
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    Are You talking about interstage between first...

    Are You talking about interstage between first stage and paraphase ? Couplings between inverter and power grids ? Or both ? Thanks

    The traces in post 79 was done without Pi coupled to the grids....
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    1.No ripple with power off. 2. The noise is...

    1.No ripple with power off. 2. The noise is coming from speaker, I can feel touching how is working when power on.
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    This is what You,re looking for, please? 55130

    This is what You,re looking for, please?

    55130
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    https://m.youtube.com/watch?v=Fx_DuHrTt6g

    https://m.youtube.com/watch?v=Fx_DuHrTt6g
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    Of course it is, but do You think is relevant for...

    Of course it is, but do You think is relevant for my issue, please ? cause I don't.
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    Are You asking about OT output with tubes removed...

    Are You asking about OT output with tubes removed ? Yes it is . This is what I get:

    55129
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