Adjusting Hallicrafters SX-85 Main Dial and Band Spread Position

Discussion in '"Boat Anchor" & Classic Equipment' started by KD2NOM, Feb 3, 2018.

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  1. KI4AX

    KI4AX Ham Member QRZ Page

    You might start thinking about changing the resistors too. A lot of those old Carbon Resistors are probably already out of specs.
     
  2. KP4SX

    KP4SX XML Subscriber QRZ Page

    Particularly the high value ones. There's probably a couple 1-2Meg ones in the AVC section that you can almost count on being way off spec.
     
  3. KK6IYM

    KK6IYM Ham Member QRZ Page

    After you have changed all the electrolytic capacitors, and the waxy paper caps, and added safety caps, and changed the out-of-spec resistors, and the weak tubes, and the three wire cord, and fuse, and re-wired the switch so black goes there not white, then you will want to re-align the radio according to the manual. That means getting a good signal generator and maybe an analog VTVM. See how much fun you are having? It won't stop with just one radio. There will be more.

    Norm
     
    G3ZBP, KI4AX and KP4SX like this.
  4. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Soooooo - if my three wire cord has two black and one green wire - does it matter which black wire goes to the fuse and which goes to the transformer primary?
     
  5. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I certainly hope so!
     
  6. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Question - when replacing the paper caps, can I use a metalized polyester film MET cap, or should I be using a Metalized Polypropylene Film PPT cap? Or should I be using the Orange / Brown dips?

    Thank you.
     
  7. KP4SX

    KP4SX XML Subscriber QRZ Page

    Doesn't matter in this application. In some physical locations you may find radial lead caps fit more conveniently than axial. But that's moot. You're replacing ones made out of PAPER! All space age plastics are infinitely better.
     
  8. KK6IYM

    KK6IYM Ham Member QRZ Page

    There are many factors that go into deciding which type of cap to buy--physical size--multilayered caps are smallest; component value--some types only come in certain values; cost--some cost a lot more; accuracy--some are rated at 5%, 10%, 20%; voltage rating--some can withstand high voltages; stability--some are much more stable and some change with temperature to compensate for an associated component changing to maintain frequency stability; some look more like the original; some work better at coupling; some work better at filtering; some fail open for safety reasons; etc.

    Over time, you will learn more and more about all these things, but for now--as Bill just stated--you are replacing waxed paper so almost anything but another waxed paper cap will perform better. I have a stock of caps--silver micas, orange dips, yellow tubulars, ceramics, electrolytics, and many times, it is really just whim or which I have more of that causes me to choose one type over another. Ceramic caps have higher voltage ratings and work well in transmitter circuits where the voltages can run quite high. They are also available in lower values. Silver micas are normally used in tuned circuits, but because they seldom fail, don't need replacement unless one is found to be bad.

    Almost everything you see over 1 MFd is going to be electrolytic. You will always want to be sure you have them with the negative going to the lower impedance side of the circuit--or the more negative side--like ground or the center tap of a power transformer. Capacitors can be combined like resistors to get to a certain value or voltage rating. Often electrolytic caps are used in series to handle higher voltages.

    Norm
     
    Last edited: Feb 6, 2018
  9. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Thank you both very much for the explanations - I'm learning so much!
     
  10. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    NOM:

    The cord should NOT have 2-black wires! That does not meet NFPA NEC! It could have blue, brown, and green/yellow. With those the brown wire goes to the fuse, the blue wire goes to the "other" side of the transformer, and the green/yellow goes to ground.

    If, for some reason, there are 2-black wires, the wire going to the smaller blade needs to go to the fuse and the wire going to the wider blade needs to go to the "other" side of the transformer. If, for some reason, both of the blades are the same size (really bad) then, looking at the end of the plug, with the ground pin down, the wire going to the LEFT hand blade goes to the fuse and the wire going to the right hand blade goes to the "other" side of the transformer.

    Glen, K9STH
     
    N0TZU likes this.

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