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Thread: 7868 tube

  1. #1
    Junior Member
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    7868 tube

    Dear All,

    Please information for 7868 pushpull amp power supply Voltage,
    I use transformer 250 Volt but this amp not work Thanks

  2. #2
    Supporting Member Chuck H's Avatar
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    There may be other reasons the amp isn't working.

    You can use lower voltage on a tube but you must also bias the tube to work with the lower voltage.

    Here is a data sheet for the 7868 tube:

    NJ7P Tube Database Search

    Chuck

  3. #3
    Supporting Member Jazz P Bass's Avatar
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    Here is a link to an RCA amplifier using 7868 output tubes.
    Link:7868 Amps

  4. #4
    Supporting Member Chuck H's Avatar
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    JPB, It's good to have a known working model to look at. The OP is less fluent in english and
    possibly understanding the electronic requirements of the circuit. I don't really know yet. If he were to follow the bias indicated in that schem with his B+ that would be incorrect. How incorrect depends.

    Is he saying he has a 250-0-250 transformer, a 125-0-125 transformer or a straigt up 250V with no CT and what kind of rectifier is he using? Is it tube rectified as in the example schem or is it diodes. And if it's diodes is it a bridge with a 250-0-250 without the CT in use, a bridge with a straight 250 secondary, a full wave with a 250-0-250 or a full wave with a 125-0-125???

    We don't really know what's going on yet so I was worried that a schematic could complicate the matter.

    Chuck

  5. #5
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    7868 amp

    Thanks for reply

    I used 6AN8 on driver and 7868 on final push pull used pioneer OT,
    power transformer output voltage is 0-250V / 200mA IN4007 telefunken rectifire full wave

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