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    M-125 Question

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    5/35

    Posts : 14
    Join date : 2014-03-01
    Location : Friday Harbor WA

    M-125 Question

    Post by 5/35 on Tue Feb 28, 2017 9:55 am

    When testing using a variac set at 12vac, shouldn't I be reading a dc voltage at the plates and screens (pins 3 & 4)? And since I am not, can I suspect a bad trans?
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    Bob Latino
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    Join date : 2008-11-26
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    Re: M-125 Question

    Post by Bob Latino on Tue Feb 28, 2017 10:32 am

    5/35 wrote: When testing using a variac set at 12vac, shouldn't I be reading a dc voltage at the plates and screens (pins 3 & 4)? And since I am not, can I suspect a bad trans?

    Do you mean a variac set to 120 VAC ? and not 12 VAC ? With the amp on with all tubes inserted, check the DC voltage from pin #8 of the rectifier tube socket to chassis ground .. If you get no DC voltage then the rectifier is not working and you will also get no DC voltage on the plates and screens.

    Bob
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    5/35

    Posts : 14
    Join date : 2014-03-01
    Location : Friday Harbor WA

    Re: M-125 Question

    Post by 5/35 on Wed Mar 01, 2017 9:29 am

    Thanks Bob,

    A zero is just a place holder..... Right?
    I'll check as you describe once I return from short road trip.

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