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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. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    This is invaluable information - thank you for taking the time to write this up for me.
     
  2. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    OK - the new capacitors are here. As well as a new three wire powercord and inline fuse. I also decided to get a desolder pump since the solder wicks were taking forever to work properly - there is a lot more solder on these connections than one would find on a PCB :)

    I also picked up an inexpensive multi-meter that also checks resistance and capacitance. I've watched some great videos from Mr. Carlson and decided to check which side the foil is on using an oscilloscope before installing the new caps.

    I am pleased with the amount of new knowledge a project like this provides!
     
  3. KP4SX

    KP4SX Subscriber QRZ Page

    You don't need to worry about the foil side with new caps. That's why they aren't marked !
     
  4. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    It is not my intention to be argumentative. As a novice in the area of electronics, I consulted this group and the internet. The information I found was that although the new caps would work regardless of orientation, the proper way to install is with the foil end connected to the point of lowest impedance or ground. This is the reference material I used:

     
  5. SM0AOM

    SM0AOM Ham Member QRZ Page

    On IF and RF frequencies at least, you do not need to worry about the "outer foil", because of the very low reactance compared to circuit impedance. If you for some reason want to exploit the non-significant self-shielding properties of foil capacitors, then connect the outer foil to "ground".

    Audiophools usually interpret various non-physically significant matters with great seriousness, which is not warranted in the much more
    practical and reasonable radio world.

    73/
    Karl-Arne
    SM0AOM
     
    KE4OH and N2EY like this.
  6. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Thank you for your thoughtful response. I will move forward with the cap replacement - part of me was just using this as an excuse to borrow an oscilloscope and become proficient at it's use.
     
  7. KP4SX

    KP4SX Subscriber QRZ Page

    If it HAS a outer foil end marked then certainly go by it. The manner in which they 'wrap' the foil and dielectric in modern caps eliminates this concern.
     
  8. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    There is an Electrolytic capacitor in a can that is marked as 30-10-10 uf @450VDC - from what I gather I should be able to purchase 2 x 10uf 450VDC and 1 x 30uf 450VDC Electrolytic capacitors and re-stuff the can with those. The issue I have run into is that I can find the two 10 uf caps leaded - however Mouser only carries the 30uf as a radial or boxed cap. Can I actually purchase a new 30-10-10 or compatible capacitor or do I need to locate a 30uf leaded cap?

    Thank you for putting up with my questions.

    Mark
     
  9. KB4QAA

    KB4QAA XML Subscriber QRZ Page

    Hey, go for it! Mr. Carlson's demonstration is interesting. If you are a detail oriented stickler, then there is nothing wrong with checking every foil cap. On the other hand, they aren't typically a problem, and time-wise it is more practical to deal with the rare problem by exception. shrug.
     
  10. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I don't think I stated that properly when referring to leaded. I meant that the 30uf is axial vs. the 10uf having the leads on the bottom.
     

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