Drake (T-4XC) T-coils dot colors

Discussion in '"Boat Anchor" & Classic Equipment' started by PA9Z, Dec 3, 2021.

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  1. PA9Z

    PA9Z Ham Member QRZ Page

    Hi Forum

    While re-aligning my Drake T-4XC, the manual says (page 5-2) that the slug alignment position depends on the color of dot on top of the slugs of T4-7. Now 3 of the slugs have off-white dots (the dot of T6 is missing), but they may also be pale yellow.

    My question: how yellow are the yellow dots? Bright yellow or very pale?

    '73 Rob PA9Z
  2. WA1GXC

    WA1GXC Ham Member QRZ Page

    I would recommend that unless absolutely necessary to adjust the coil-slug screws due to prior misalignment or tampering by a previous owner, do
    not adjust the screws in any way. The ferrite slug/screw assembly is somewhat delicate and if frozen and you do not want to risk damaging it.

    There should be enough adjustment-range utilizing the RF trimmers/Injection trimmers array on the side of the transmitter--adjusting for every band
    during this same procedure--to bring all transformer circuits--T4, 5, 6, 7 into resonance.

    If you find you require maximum capacitance (fully tight adjustment on any trimmer), you may re-position the "RF TUNE" control to very slightly lower
    frequency on any band with the front-panel control--that will give more inductance--and you will be able to re-adjust the associated trimmer capacitor to a less-tight
    position to achieve resonance and maximum drive power.

    If you look at the very small dimension differences in the manuals--white dot, yellow dot, etc.--you will see it is not even 1 mm difference. I know I cannot
    reliably measure that adjustment precisely with the transformers installed in-place.
    I suspect your off-white dots are faded yellow with age. Measure the lengths and if they seem
    reasonable, in accordance with specifications, just proceed as above with trimmers.
    Good luck!

    Last edited: Dec 4, 2021
    K7TRF likes this.
  3. PA9Z

    PA9Z Ham Member QRZ Page

    Thanks Harris again for your good advice. Indeed, I did not touch the sealed screws of the individual slugs, I only adjusted the whole beam connected to the wired mechanism.

    Indeed the differences of the settings between the various coloured slugs is minimal. I wondered why there is a difference in the adjustment settings anyway.

    In the mean time I was able to adjust the coils. I also replaced the two finals and the rig is now producing a nice 100W+

    73 from the Netherlands!

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