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

    Well, the ferrite core assortments I ordered from Talon came today but unfortunately out of all 40 various slugs, not ONE of them was the correct diameter - they were are 1/8" or smaller - so I'm still in the market ...
  2. K9STH

    K9STH Ham Member QRZ Page

    Just which band ranges do you need the slugs for? Or, for i.f. cans?

    I have the remains of a parted out Hallicrafters S-40A that used, if I remember correctly, the same, basic, coils as the later S-85. There may be some of the slugs still around. I don't remember if the i.f. cans were the same. Somewhere in the S-40- series they went to smaller sized i.f. transformers, maybe even with the S-85 / S-86 versions.

    Glen, K9STH
  3. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    The one I need most is for the oscillator trimmer (C19). It's a 1/4" diameter by 3/8" slug - flat on one end and slotted for a non-conductive tool on the other. I also need one for the top slug of the 3rd IF can - but that is actually aligned at this time and not as pressing (it also appears to be 1/4" diameter but has a recess in the bottom to accommodate the ferrite coil transformer plate.

    Please note that the pictures are not of my particular IF Transformer but that is the style.

    download.png images.jpg
  4. K9STH

    K9STH Ham Member QRZ Page

    Methinks you are confused! C-19 is a mica trimmer capacitor and there is not any slug involved, only a flat piece of mica that is between the fixed plate and the movable plate that is adjusted by turning the machine screw that is in the middle.

    Do you actually mean a slug for L-7? L-7 is used to adjust the low end of Band 4 and C-19 is used to adjust the high end of Band 4.

    Both C-19 and L-7 are contained in a single assembly but are definitely different components.

    Glen, K9STH
  5. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Methinks thou art correct - it IS L7 - the Oscillator Slug that is broken.

    Thanks for keeping me honest Glen!
  6. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    I think I have found a working solution for the slug and will update you in a little bit. I've replaced the damaged slug and have replaced all the tubes as well (I ordered a replacement set). I'm letting the radio warm up and then will be aligning her.

    I have a question - with the radio turned on, the volume and sensitivity set to minimum, and the radio in the standby OR receive position (no antenna connected) I get a little bit of static every now and then - maybe once every five minutes or so. I don't see any arcing. I have recapped the radio but not replaced the resistors (yet).

    I can turn the main tuning dial and find a point of loud static and can reproduce it once I find it (tuning up and down around it).

    What should I be looking at to locate and correct this static?

  7. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Sigh - I tried using carbon steel set screws with an oxide finish in the radio to replace the damaged ferrite tuning slugs - alas - they fit beautifully and are very easy to adjust, however the cause the band to be well over 4 MHz off on the lowest band. I'll continue looking to source the correct slugs - I may have to actually purchase another S-85 to get enough parts to build one ....
  8. K9STH

    K9STH Ham Member QRZ Page

    Look for something shorting out the plates of the tuning capacitor at the point where the static happens. This could be anything from a bent plate to a burned place on the plate to just plain dirt / dust on the plate.

    Glen, K9STH
  9. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    Thanks Glen - I see the main air capacitor has a bent plate on the far end - I'll make some adjustments and see what I see.
  10. KD2NOM

    KD2NOM XML Subscriber QRZ Page

    So - I declare success!

    Unable to source a ferrite slug, I decided to figure out how to use the ones I have. since they were only broken on the one end, I flipped them around and used a rotary tool with a diamond tip and made my own adjustment tool slot. Worked like a charm. I completed the alignment procedure outside of the chassis to make sure I could get it close and will do it again now that it is in the chassis. I am able to tune across all the bands using my 40 meter dipole and to some extent, using my 10 meter vertical.

    I put the original tubes back into the radio before tuning it as the replacement 6K6-GT arrived severely burnt and causing a wicked hum in the radio when powered on regardless of volume settings.

    Additionally, the UHF/VHF matching transformer did not work at all - it really lowered the overall signals coming in - as soon as I removed it I was amazed by the number of stations I am receiving.

    I learned a WHOLE lot about basic electronics and RF with this project - and I know I still have volumes to learn.

    Many thanks to everyone who helped - especially Glen!

    I'll post a final description of all the work done.


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