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Thread: Trinity Tramp - EL34/6L6 switch question

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    Member Fred G.'s Avatar
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    Trinity Tramp - EL34/6L6 switch question

    Hi All,

    I'm in the final stages of building a Trinity Tramp. I'm confused about the "behavior" of the EL34/6L6 switch. Here's what's happening:

    I wired the switch according to the instructions. It's a DPDT switch. The "top" two lungs are jumpered together, as well as connected to the EL34 2.5k tap. The "bottom" two lugs are jumpered togetherand wired to the 6L6 5K tap. The center two lugs are wired together, and that goes to the octal socket.

    After I wired this, I did a continuity test on the switch to verify everything was working properly. I expected the switch to show continuity from the center lugs to EITHER the "top" or "bottom" lugs, BUT - INSTEAD, there was total continuity across the entire set of lugs, regardless of switch lever position!!!

    I took everything apart and tested the switch, and it worked as expected. Re-wired everything, and again found continuity across every lug in the switch, regardless of the switch lever's position..

    I'm guessing this has something to do with the way the transformer is constructed, but I sure as hell don't understand it. Can somebody explain this phenomenon to me?

    Thanks in advance!

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    Lifetime Member Enzo's Avatar
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    If you would post or link the schematic of what you are building it will be much easier to comment on.

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    Member Fred G.'s Avatar
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    Quote Originally Posted by Enzo View Post
    If you would post or link the schematic of what you are building it will be much easier to comment on.
    https://www.trinityamps.com/docs/TrampSchematic19.pdf

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    How are you measuring 'continuity'? If you are using the continuity range on a DMM it will probably indicate continuity through the resistance of the winding. Try measuring on the DMM 200ohm range, that will show the difference between the switch dead shorted and the winding resistance.

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    Member Fred G.'s Avatar
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    Quote Originally Posted by Dave H View Post
    How are you measuring 'continuity'? If you are using the continuity range on a DMM it will probably indicate there is continuity through the resistance of the winding.
    Dave,

    That is EXACTLY how I was measuring. I guessed it had something to do with the way it was reading "through" the winding, but I wanted some verification. I'm still just getting my mind around how this would occur through the switch - it sure threw me for a loop last night, though.

    Thanks!

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    When you are measuring continuity or resistance of a transformer winding, the meter only sees a piece of wire and measures its copper DCR.

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    Member Fred G.'s Avatar
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    But I was measuring across the SWITCH - this is what confused me (and still kinda does).

    I'd have thought I'd see continuity between the center lugs and either the top or bottom lugs, depending on which way the switch was thrown.

    Instead, it was "mass continuity" - lol. No matter how the switch was thrown, there was complete continuity across ALL lugs.

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    Lifetime Member Enzo's Avatar
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    Totally has to do with the winding. From the two end terminals of the switch you have the winding. Whatever its resistance might be, it will be low.

    "Continuity" readings are for guys wiring houses. Use the resistance scales.

    Look at the schematic. Those two terminals are directly wired to the transformer winding. Imagine you were measuring between those two places and the switch itself was gone.

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    Lifetime Member Enzo's Avatar
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    This sort of thing comes up more often than you might think. People often write in claiming a bunch of resistors in their amp measure very low. It is because of other circuit paths in parallel with the resistor. You can never forget everything is in a circuit, nothing stands alone in the world. Unless you are just measuring a resistor from the drawer. The circuits often have other circuit paths connected to a part in question.

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    Member Fred G.'s Avatar
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    Quote Originally Posted by Enzo View Post
    This sort of thing comes up more often than you might think. People often write in claiming a bunch of resistors in their amp measure very low. It is because of other circuit paths in parallel with the resistor. You can never forget everything is in a circuit, nothing stands alone in the world. Unless you are just measuring a resistor from the drawer. The circuits often have other circuit paths connected to a part in question.
    OK, looking at the schematic, I can visualize what is happening here. It was just so counter-intuitive (to me, at least) that I couldn't buy into what was actually happening at first.

    Thanks for all your answers!

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