Johnson Valiant Drive Issues

Discussion in '"Boat Anchor" & Classic Equipment' started by N1BCG, Dec 21, 2016.

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  1. N1BCG

    N1BCG Ham Member QRZ Page

    Suffering from low drive?

    Several Valiants have come across the workbench with this issue, so I decided to share the secret to restoring that Valiant libido to where it should be and with only minor invasive surgery!

    "Valiant A", as we'll call it, had nearly no drive on 20M. "Valiant B" had widely varying drive on the upper bands. In both cases, the 5763 would not be able to create the specified 7.5 mA of PA grid current, and high settings of the DRIVE pot would cause saturation.

    As it turns out, later factory wired Valiants and all Valiant IIs have an additional coil "L6C" mounted to the SW3A band selector switch which increases the inductance and Q of the driver tank circuit.

    L6C can be easily made with 12 turns of insulated solid conductor hookup wire tightly wound on a 3/8" diameter (I used a drill bit). Installation is simple:

    1) Red wire from driver tank coil removed from terminal #4 on SW3A. Insulate the end as it will not be used.
    2) Green wire from driver tank coil moved from terminal #5 to terminal #4 on SW3A.
    3) L6C installed between terminals #4 and #5 on SW3A.

    The attached schematic shows the change of heart the E.F. Johnson engineers had late in the original Valiant production run that became the norm for the Valiant IIs.

    You should see an improvement in drive for 20M and up or your money back. Not recommended for 11 meter operation. Use as directed.

    Last edited: Dec 21, 2016
    N2EY likes this.

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