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. KP4SX

    KP4SX XML Subscriber QRZ Page

    You might search for 33uf which is the 'standard' nowadays.
    Look for the skinny Nichicon caps about the thickness of a pencil. They are great for restuffing. Typical part number at Mouser 647-UCS2W390MND9.
    20180214_073504.jpg
     
    KA0HCP likes this.
  2. SM0AOM

    SM0AOM Ham Member QRZ Page

    I believe it would be extremely difficult to locate a can type 30+10+10 µF electrolytic today.

    There is nothing "sacred" about the values of filtering capacitors, so for simplicity, use 3 pieces of 33 µF 450V
    electrolytics and re-stuff the can with them if they fit mechanically. The end result would be the same.

    73/
    Karl-Arne
    SM0AOM
     
    N2EY likes this.
  3. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Excellent! I have a bunch of E-caps on their way already.
     
  4. W2WDX

    W2WDX Subscriber QRZ Page

    One other point on resistors. If you do find some that need to be replaced its is important to replace them with non-inductive types, especially in RF circuits. Some resistors, like wire-wound can add inductance to a circuit causing unpredictable results like oscillations. Just to be sure I always use carbon composition; however, other non-inductive types work fine.

    On filtering capacitors, to say there is nothing sacred about values is sort of true, but should carry a caveat. Voltage ratings should be nearly twice the working voltage of the circuit, or as close to that as practical. Also, significantly increasing capacitance will not improve filtering, but may increase in-rush currents at levels that can stress the power transformers (or chokes if used) when power is applied.
     
    Last edited: Feb 14, 2018
  5. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Great info - next step is to start testing resistors.
     
  6. W2WDX

    W2WDX Subscriber QRZ Page

    I added something more with an edit.
     
  7. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Understood and thanks for the additional information.

    All the paper caps have been replaced with 630v caps with the exception of the 250VAC safety cap I put in at the AC input.

    The electrolytics are getting replaced with the three identical (but new) rating e-caps
     
    KP4SX likes this.
  8. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Update:

    - Replaced all the paper wax caps
    - Replaced the Electrolytic caps under the chassis
    - Upgraded the main power cap with a safety AC cap
    - Replaced the power cord with a 3 wire, inserted a 3 Amp fuse and ran a ground to chassis
    - Have a 30/10/10 Electrolytic Can Cap coming from Hayseed Hamfest (https://hayseedhamfest.com/collections/hallicrafters/products/s-85-re-cap-kit) - they actually have a re-cap kit - oh well, I figured out how to source all my caps and have spares now.

    Once the Can Cap is replaced i'll test the tubes and then fire her back up. I spot checked several resistors and they were all still within spec - so we'll see how she receives. I'll align her after all that.

    Thanks for all the input!

    s-85-recap1.jpg s-85-recap2.jpg
     
    KA0HCP likes this.
  9. KP4SX

    KP4SX XML Subscriber QRZ Page

    Bravo! Sounds like you are doing everything right. I might quibble about a 3A fuse though :)
     
  10. KD2NOM

    KD2NOM XML Subscriber QRZ Page


    Ahhh - I see your point - I was advised to put in a 2A fuse - I will replace that.
     

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