Help with not standard transformer

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JLouis
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Help with not standard transformer

Post by JLouis » Thu Jan 11, 2018 6:05 pm

Hello

Just got a used Metropoulos serie 10’000 (Year 2012) from US (110v). After changing the connection for Europe (230v), the fuse blew (amp ON and Standby ON). The PT seems be working with no shortcut (tested) but the secondary voltage are far higher than they should be (approx 1.5 times).

The PT wire colours are not to standard:
Primary (in order) Orange - Yellow - Red (110v) - Blue - Brown
Secondary:
    Heater: 2 Green thick 1 Green thin
      Bias Green and White,
        Main voltage (in order) Yellow - Blue - Grey - Black

        I try to figure out where the prob. come from but with no success so far.
        Any help should be appreciated :help:

        Thanks.

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        neikeel
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        Re: Help with not standard transformer

        Post by neikeel » Fri Jan 12, 2018 3:24 pm

        I suggest you contact George if it is one of his builds, he will be able to advise on the correct primaries for your area.

        Tends to have common, 120v, 220v and 240v wires, so the common should be the same for all areas, the red is usually 120v (i.e. US) .

        You might be able to 'ring' the windings out with a good meter, I believe Orange is common.

        Common to 240v will have highest R and 120v lowest R with the one you want being the middle. I suspect you hooked up to the 240v tap - hence the high voltages. Blue is normally 220v and purple (is yours brown or purple?).
        Neil

        JLouis
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        Re: Help with not standard transformer

        Post by JLouis » Sat Jan 13, 2018 3:56 pm

        Thank you Neikeel

        George already advised me that the brown is the right one.
        Nevertheless I checked the value as you mentioned and got the following figures:

        Primary:
        Orange - Yellow 0.9 Ohm
        Orange - Red 1.0 Ohm
        Orange - Blue 1.2 Ohm
        Orange - Brown 1.7 Ohms

        Secondary:
        Bias - 35 Ohms
        Power 14 Ohms
        Heater is very low 0.2 Ohm but the power light goes ON before the fuse blow. I conclude that there is no shortcut here.

        What I don’t understand is why the secondary voltage is so high:

        Instant lecture before the fuse blew:
        Bias 150vrms
        Heater 10vrms
        Power 500vrms

        I checked the value of the filter capacitors and the diode bridge - both are fine
        Also the connection to the bias with the resistor and the diode, fine as well

        I am puzzle :scratch:

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        neikeel
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        Re: Help with not standard transformer

        Post by neikeel » Sun Jan 14, 2018 11:11 am

        It sounds very much like your wall voltage is 'high' for the selected tap, so if you are using the blue 220v tap (mainland Europe) then use the brown one as if you are receiving 240v and see if that drops the voltages across the board
        Neil

        JLouis
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        Re: Help with not standard transformer

        Post by JLouis » Sun Jan 14, 2018 1:17 pm

        Just disconnected the transfo and the fuse blew again :palm:

        Also took some measures and obtained almost the same than previously

        Primary 230 Vrms (normal for Switzerland)
        Secondary
        Heater 10 Vrms
        Power vs CT 300 Vrms
        Total power 609 Vrms
        Bias 150 Vrms

        Need to be replace but this trans will remain a mystery for me :scratch:

        JLouis
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        Re: Help with not standard transformer

        Post by JLouis » Sun Jan 14, 2018 1:26 pm

        Thank you Neil for your post.

        Already use the brown tap as the wall voltage is 230v in Switzerland .
        It seems as this transfo is not wired/adapted for my country and need to be replace.

        I contacted George for advice, may be he kept some notes on that transfo when he built this amp.

        Thx again for your help :toast:

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