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  1. #1
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    Question Old tube receiver connection symbols?

    I recently acquired a Martel/Rotel FAX-150c tube receiver made in the 1960's. Stamped on the rear chassis beneath the speaker screw connections are the following:

    right 0 8 0 8 left

    So is the 0 the positive or is the 8 the positive?

    Under the FM/AM group the following is stamped on the chassis beneath the screw connections:

    FM G AM

    Would I use the G ( only ground I see ) to connect the phono ground wire?

    The phono inputs are marked MAG and X-TAL so the MAG would refer to a magnetic cart but what is X-TAL?

  2. #2
    Suspended markw's Avatar
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    Quote Originally Posted by Poultrygeist
    I recently acquired a Martel/Rotel FAX-150c tube receiver made in the 1960's. Stamped on the rear chassis beneath the speaker screw connections are the following:

    right 0 8 0 8 left

    So is the 0 the positive or is the 8 the positive?
    It doesn't matter which is which as long as you are consistent. Logically, I would use 8 as the positive.

    Quote Originally Posted by Poultrygeist
    Under the FM/AM group the following is stamped on the chassis beneath the screw connections:

    FM G AM

    Would I use the G ( only ground I see ) to connect the phono ground wire?
    No, that's for antenna connections. For a phono ground use a screw on the metal chassis. Many receivers have a knurled knob for this purpose but any screw on the chassis will do in a pinch.

    It sounds like the receiver has only 300 ohm twin lead connections for FM. The antenna would be connected to the FM & G connections. A long-wire AM antenna would go to the other.

    Quote Originally Posted by Poultrygeist
    The phono inputs are marked MAG and X-TAL so the MAG would refer to a magnetic cart but what is X-TAL?
    Correct. The MAG input is used for a magnetic cartridge. XTAL refers to old, obsolete high-output crystal (or ceramic) cartridges that aren't used any more. That input lacks the gain and RIAA curve required for magnetic cartridges.

  3. #3
    ISCET CET, FCC CTT, USITT Dual-500's Avatar
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    "0" will be the common which may or may not be floating from chassis ground. As such, "8" will be the hot or "+" and should be in phase with the input signal.

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