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Thread: Beam Pentode orientation in relation to mains transformer

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    Beam Pentode orientation in relation to mains transformer

    I am confused by a Morgan Jones illustration on pg 10 of this book, Building Valve Amplifiers -- https://drive.google.com/file/d/0B6x...ew?usp=sharing

    I think he means that the proper tube orientation is the tube on the left in the first pic, is that correct?
    Click image for larger version. 

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    Here is another angle
    Click image for larger version. 

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    Edit: 2nd pic is not the orientation I wanted. I have no idea why that image flipped sideways and the other is in normal orientation

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    As best I can tell, you have it right.

    Thanks for that - some neat-looking ideas for construction there.

    Justin

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    Justin, Im with you. I 90% believe that the left tube is correct orientation.

    Anyone else ??

    I tried to scan to where I thought it might talk about this in the RCA manual but it was page 1024. Not a good page to try for on a PDF format

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    I would think the only way to know for sure is to dissect-a-tube & figure out where the BFPs are... Or, what kind of tube is it, and maybe someone has already sacrificed one?

    Or just leave an extra inch on the tube socket wire, and if it makes noise, rotate the socket...

    Justin

    And which RCA manual? Biggest one I have is RC30, 762 pages. Maybe it's downloadable somewhere!

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    "... If an older Boogie and classic Marshall had a (clearly illegitimate) child and you baked it in an oven set to clown shit crazy." - Chuck H. -
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    He's showing the orientation of the electron beams controlled by the beam-forming plates...he's orienting the tubes (and thus the beams) to flow "parallel with" the possible magnetic disturbance field coming from the transformer; ie: plate electron beams in same plane/orientation as transformer core plates (not the windings).

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    Click image for larger version. 

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    This picture answers a lot of questions for me.

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    Although rather "hard" on the tubes, simply increasing its idle current until it "red plates" will also *show* you exactly where the "beams" are hitting, since where the plate turns red first is where the beams are hitting.

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    Or this similar picture:
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