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Thread: Mercury Magnetic Power Tranny

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    Mercury Magnetic Power Tranny

    Hi, im building a Ceriatone 5e3 from this layout: http://www.ceriatone.com/images/layo...one_080508.jpg
    I have Mercury Magnetics Transformers for it, but the voltages on the PT seems to be different although it is a Tone Clone tweed deluxe PT. On the Layout B+ is 325V, and on the chart for my Tranny it is labeled 380V, which seems like a very big difference to me. Is this ok?? I understand from other threads that i can lower the voltage by using a NOS 5y3, but I don?t have one. If this is a possible fix, can i use the sovtec 5y3 that i have and switch it out later without causing harm?
    The Filament wires on the layout are labeles 3,15V and on my PT they are 6,3. I?m guessing that is some parallel/series thing, but I just want to make sure how to wire those before I make mistakes as this is my first amp build.
    Finally, I have read in some other thread that grounding the Center Taps from both B+ and Filament on the MM PT will fry the Tranny. Can that be right?? In this thread: http://music-electronics-forum.com/s...ead.php?t=6235 it is pointed out that if a 5V CT is there it should not be grounded, so maybe that was confused with the filament ct in the other thread... On the layout both B+ CT and filament CT are grounded.
    Sorry for the stupid questions, but help will be greatly appreciated.

    Edit: link

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    Last edited by Steel Duck; 07-29-2008 at 10:26 AM.

  2. #2
    Old Timer
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    We need a bit of clarification here, are we talking 325v/380v AC or dc? Loaded or unloaded?

    Tone Clone is a brand name, not a mission statement, MM offer a whole bunch of options, they can't all be right.

    A Tweed deluxe (or clone) might run 350-385vdc after the rectifier (NOS 5Y3) BUT unless MM knew what rectifier you were using they wouldn't know this and I doubt they would include it as a a spec for a PT. Confirm with them what dc voltage you should see after a NOS 5Y3. 380-0-380VAC rated secondary B+ winding will NEVER give you 5E3 type voltages. 330-0-330VAC B+ secondary will be about right.

    The Sovtek 5Y3 isn't really a 5Y3, if you really want to use a 5Y3 buy NOS, or maybe try a 5V4, these are very popular for 5E3.

    Your heaters will measure 3.15VAC from each leg to ground, really you want to measure from pin 2 of a 6V6 to pin 7, you should see >6.3VAC.

    Centre taps from B+ & 6.3VAC heater windings should be grounded, there is not usually a centre tap for the 5VAC rectifier winding (though Hammonds have them). Confirm?

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    Hi, thanks for the reply.
    This is what i could find on MMs homepage: Tweed -- stock B+ -- 380-0-380 unloaded. The information that followed was a chart of the leads identical to the one on this document: http://taweber.powweb.com/store/merc/FTDP.pdf
    The sovtec 5y3 isn?t really a 5y3? Will i be able to use the sovtec, but it just won?t sound the same, or is it a completely different annimal? I think ive heard some people use the sovtec, but the reason i got it i must admit is it was the only brand my suplyer had

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  4. #4
    Old Timer
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    Well, it's what you have so go with it, they seem to imply "correct" final voltages.

    The Sovtek will give slightly higher final B+ voltages, with the stock circuit & 250/270ohm cathode resistor you don't really want much over 385vdc, or 40mA, on the 6V6 plates (measured to ground). If you do have more than this it would be sensible to sub the cathode resistor for 300-330ohms.

    5V4s are plentiful, have a tighter response and slow warm up.

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    Thank you very much. I will build it with what i have now and be mindfull of the voltages. Then try the 5v4 or a NOS 5y3.

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    I'm using one of there out put trannys now the FTDO-59M has different taps for 6v6 or 6l6 on my next build think I'll try your PT

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